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OPERATION AND MAINTENANCE HANDBOOK

FOR

MODEL 608D

VHF SIGNAL GENERATOR

Page 2,

Page 4,

Page 4,

Page 4,

Page 8,

#608D006

ERRATA

Paragraph 1-3, line 14:

change 1'0.5 milliwatt" to "0.1 milliwatt".

Specifications, Output Level Calibration Accuracy:

change "12 decibels" to "±l decibel".

Specifications, External Sine Wave Modulation:

change "4 to 25-volt rms signal required" to"0.5-volt rms or better r- -~uired".

Specifications, External Pulse Modulation:

change "Positive la-volt peak pulse required" to"Positive 5-volt peak pulse required".

Figure 2, item 20:

arrow should point to recessed screw above ZERO

i

OPERATION AND MAINTENANCE HANDBOOK

FOR

MODEL 608D

VHF SIGNAL GENERATOR

Copyright 1955 by Hewlett-Packard Company

The information contained in this bookletis intended for the operation and main­tenance of Hewlett-Packard equipment andis not to be used otherwise or reproducedwi thout the written consent of the He lett­Packard Companyo

HEWLETT-PACKARD COMPANY275 PAGE MILL ROADs PALO ALTOs CALIFORNIA, U. S. A o

•

Section I

Section II

TABLE OF CONTENTS

MODEL 608D

VHF SIGNAL GENERATOR

GENERAL DESCRIPTION

1 -1 Intr oductory. . . • . • . • . . .1-2 Auxiliary Equipment . • . • . . •1-3 General Electrical Characteris tics.

INSTALLATION AND OPERATION

Page No.

112

-.D2 -1 Introductory.0 · . · · · · , 5

0 2 -2 Installation 5(:l · . · · · , ·co 2 -3 Operating Controls, Dials, and0-.D Terminals · , · · · · 5'* 2-4 Turning on the Equipment 6

Q) 2 -5 Continuous Wave Operation · 11> 2-6 Internal Sine Wave Modulation 120.0' 2 -7 External Sine Wave Modulation 13

cO 2 -8 Pulse Modulation 14""d · · · · · ·

r.= 2 -9 Crystal-Controlled Beat FrequencyIII t Calibrator 15· , · · · ·N 2-10 Signal Generator Loadingcr-..... Considerations 15· , · ·.....

2 -11 Adjust. Control 16acO Fine Freq. ·....1-tQ)

U)

Section III THEOR Y OF OPERATIONIl'lIl'l"-.. 3 -1 General 17cr- . . · , ·..... 3 =2 Radio Frequency Oscillator 19"-..Il'l 3-3 Radio Frequency Buffer · · · . 20

3-4 Radio Frequency Power Amplifier · 21(:l 3 -5 Output Attenuator and R-F Powerco

Monitor 220 . · , · · , , ·-.D 3-6 Xtal (B eat Frequency) Calibra tor 233-7 Modulator Section · · · · · · 243 -8 Modulation-Measuring Circuits · · . . 263-9 Power Supply · · , · , 263-10 Heater Supply Multivibrator • · 27

Section IV

TABLE OF CONTENTS (Contd.)

MAINTENANCE

Page No.

4-14-24-34-44-5

4-64-74-8

4-9

4-10

4-11

4-124-134-14

4-15

4-16

4-17

Introduction. . . • . . . . . . .Cabinet Retnoval ..•.....Periodic Checks and Routine Care.Localizing Trouble .Power Supply Trouble Shooting and

Adjusttnent .Systetn Analysis Check Chart . . .Replacetnent of Electron Tubes . .Radio Frequency Oscillator Tube

Replacetnent . . . • . . .Radio Frequency Atnplifier and

Buffer Tube ReplacetnentXtal Frequency Oscillator Tube

or Crystal Replacetnent . .Replacetnent of Electron Tubes

Within the Regulated PowerSupplies . . . . • . .

Attenuator Probe ReplacetnentReplacetnent of Latnp IICalibration of the Percent

Modulation Meter . • .Output Volts Meter Calibration and

R-F Power Monitor ServiceRepairing the Calibrator

Oscillator . . . . .Trouble Shooting Chart

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LIST OF ILLUSTRATIONS

Page No.

VHF Signal Generator =hp- Model 608D, . Y:;ooI"tispieceModel 608D Signal Generator Front Panel

Controls ., 0 0 <1 :) 0 • ~ ~ :J <1 I' <1 8Diagram Shovling Relationships of Front

Panel Controls to Major Circuits 10Block Diagram for Signal Generator 608D 18Cabinet Removal Diagram • 0 • 0 0 0 30R-F Tuner Drive Mechanism 0 , 0 • 32Tube Location Diagram • 0 , • • • 42R-F Oscillator and Amplifier Tube

Replacement Diagram .?.. 44Diagram Showing Adjustment for

Internal Freqo Calibrator • . 46R-F Generator Assembly Rear View r

Showing Output Attenuator Drive System 48R -F Output Attenuator P~ obe~ Showing

Pickup Loop and Impedance MatchingNetwork ••. 0 • • 0 0 • • • 0 50

Model 608D Signal Generator Right SideView g Cabinet Removed, • • . . , , . •. 64

Model 608D Signal Generator Rear ViewgCabinet Removed •.• 0 , • • • 65

Model 608D Signal Generator Left SideView p Cabinet Removed. 0 • 0 .0 0 • 66

R-F Generator As emblyg Side PlateRemoved to Show Tuning Compartments 67

Tube Compartment of R-F GeneratorAssembly, Frequency Dial and CoverPlate Removed • 0 0 0 0 0 • 0 68

Signal Tracing Block Diagram 69Tube Socket Voltage and Resistance

Diagram g Right Side Chassis 71Tube Socket Voltage and Resistance

Diagramg Rear Chassis. 0 • • 0 73Tube Socket Voltage and Resistance

Diagram 9 R-F Generator Assembly 75

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Fig. 1. VHF Signal Generator -hp- Model 608D

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1-1

1-2

SECTION I

GENERAL DESCRIPTION

INTRODUCTORY

The Hewlett-Packard Model 608D VHF Signal Generator is ageneral purpose test instrmnent which furnishes accurately adjust­able radio frequency signals from 0, 1 microvolt to 0.5 volt overthe frequency range from 10 to 420 megacycles and which may beamplitude modulated by internally generated sine waves or by ex­ternally applied sine waves or pulses. The 608D includes a built­in crystal-controlled heterodyne calibrator which permits theoperator to adjust the output frequency very accurately at checkpoints every 5 megacycles over the full frequency range of the in­strument. The output signal level is adjusted by an attenuatorcalibrated in both volts and dbm and can be read directly to anaccuracy of ±1 db over the full frequency range without the use ofexternal pads, monitoring devices. or charts. The 608D featuresstraightforward operation through the use of reliable. direct­reading controls and meters throughout. With its high quality out­put signal, the -hp= Model 608D is especially suitable for applica­tions requiring a minimum of incidental amplitude or frequencymodulation.

The Model 608D Signal Generator is designed to meet the exactingrequirements of precision laboratory work and yet to be equallyuseful for general applications in the 10 to 420 megacycle frequencyrange. The equipment can be used for testing, calibrating. andtrouble shooting VHF radio equipment and circuits and for measur­ing standing wave ratios, antenna and transmission line character­istics, receiver sensitivity, etc. To obtain utmost accuracy inthis type of application. particular care has been taken -in the de­sign of the 608D to hold spurious modulation to a very low valueunder all operating conditions.

AUXILIARY EQUIPMENT

The Model 608D Signal Generator is a complete test equipmentready for use as received from the factory. A special wrenchneces sary for removing the r -f amplifier tube is supplied and ismounted on the instrument chassis. To use the crystal calibratorincluded in the equipment, an earphone headset must be providedby the operator. For external modulation of the signal generator.an external source of modulating voltage must be provided by theoperator. A special coaxial fuseholder for protection to the output

-1-

attenuator is available as an accessory. This fuse protects theoutput attenuator from. dam.age in the event that an external voltageis accidentally applied to the RF OUTPUT jack, The fuseholderconnects directly to the output jack and is provided with a standardfem.ale type N output jack. A type 8AG s 1/16 am.p fuse is utilized.The fuseholder has an insertion loss of 0.50 db at 200 m.c. 0.56db at 300 m.C t and 0.65 db at 400 m.c; and its VSWR is not greaterthan 1. 35 when connected to a 50-ohm. resistive load.

1-3 GENERAL ELECTRICAL CHARACTERISTICS

The Model 608D generates r -f output signals over the frequencyrange from. 10 to 420 m.egacycles which are indicated on a direct­reading dial. The frequency dial calibration is accurate to betterthan 1% when the m.ovable index is in its original position as indi­cated by the alignm.ent of the adjustm.ent knob with the white lineon the panel. Calibration accuracy m.ay be im.proved by em.ploy­ing the crystal-controlled heterodyne calibrator. which providescheck points at every 5 m.egacycles over the entire frequencyrange of the equipm.ent. The frequency dial index is adjustablefrom. the front panel so that at any check point the calibration m.aybe set very close to the calibrator accuracy of 0.01%. The check­point signals are obtained by connecting an earphone set (not partof the equipm.ent) to the XTAL CAL. OU1PUT jack. The cali- " JJ

brator is capable of providing up to-e-;-s:m.illiwatt of power to a ./600-ohm. headset and is adjustable by the XTAL CAL. GAINcontrol.

An output attenuator. calibrated to be read directly in both voltsand decibels. continuously varies the output signal from. +4 to-127 dbm. (350 m.illivolts to 0.1 m.icrovolt) and m.ay be read to anaccuracy of ±l db or better over the entire frequency and attenu­ation range when connected to an external 50-ohm. resistive load.The internal im.pedance of the generator, as seen at the outputjack. is nom.inally 50 ohm.s over the full frequency range; andwhen connected to a 50-ohm. resistive load, the VSWR due to m.is­m.atch will not be greater than 1. 2 (SWR of 1. 6 db).

The r-f output signal from. the 608D m.ay be am.plitude m.odulatedby internally generated 400- and 1000-cycle sine waves or byexternally applied sine waves above. 5 volt rm.s over the frequencyrange from. 20 cps to 100 kc or by externally applied pulses aboveapproxim.ately 10 volts, When pulse m.odulated. the 608D is capableof generating pulses of radio frequency energy as short as 4 m.icro­seconds at r -f signal frequencies above 40 m.egacycles and pulsesas short as 1 m.icrosecond above 220 m.egacycles. The degree ofsine wave m.odulation is continuously variable from. 0 to 95% by afront panel control. All sine wave m.odulation of the r -f output

-2-

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signal is continuously monitored and indicated in percentage on adirect-reading modulation meter having an accuracy of ±10% ofthe meter indication at readings between 30 and 95%.

The emrelope of the sine wave modulated signal contains less than5% distortion. Incidental amplitude modulation of the CW out?utsignal is less than 0.1%, The total L'?vel of harmonics and spurioussignals contained in the CW output signal is 40 decibels below thelevel of the output signal when the output level is greater than 200mi crovolts.

R-f leakage is held to a minimum and is such that when the outputsignal is adjusted for 0.1 microvolt. the conducted signal leakageat any other front panel connector and the radiated leakage twoinches from the instrument are each less than L 0 microvolt.

The 608D is 13 -3/4 inches wide by 16 inches high by 20 inchesdeep and weighs 64 pounds. The ins trument is housed in an alu­minum cabinet finished in gray baked enameL Guard-rail typehandles are provided to assist in handling and to protect the frontpanel controls. Ventilation is provided by louvers in the side andback surfaces of the cabinet. The chassis is removable by loosen­ing the four screws in the rear of the cabinet.

-3-

SPECIFICATIONS FOR THE MODEL 608D SIGNAL GENERATOR

FREQUENCY RANGE:

ACCURACY OFFREQUENCY CALIBRATION:

CRYST AL CALIBRA TOR:

OUTPUT VOLTAGE:

OUTPUT LEVEL METER:

OUTPUT LEVELCALIBRATION ACCURACY:

RATED LOAD:

OUTPUT CIRCUITSTANDING WAVE RATIO:

INTERNAL MODULATION:

EXTERNAL SINE WAVEMODULATION:

PERCENT MODULATION:

ENVELOPE DISTORTION FORSINE WAVE MODULATION:

INPUT IMPEDANCE FOREXT SINE MODULATION:

EXTERNAL PULSE MODULA TION:

INPUT IMPEDANCE FOREXT PULSE MODULATION:

FREQUENCY STABILITY:

RESETABILITY:

RESIDUALFREQUENCY MODULATION:

LEAKAGE:

10 to 420 megacycles covered in five bands.

With crystal calibrator, to. 050/0 at checkpoints. Without calibrator, to. 5% overall.

5 megacycle oscillator accurate to to. 01%providing check points at each 5 megacyclesover full frequency range. Provides O. 1milliwatt or better to 600-ohm earphone set.

Continuously adjustable from 0.1 microvoltminimum to 0.5 volt maximum when operatedinto rated load of 50 ohms.

Monitors r-f power level fed to output attenu­ator; calibrated a to 7 dbm and 0.1 to 0.5 volt.

For all conditions of operation the accuracyof the attenuator dial is within t2 decibelswhen operated with 50-ohm load.

Nominally 50 ohms resistive.

The VSWR measured at the output connectoris less than 1. 2 (SWR 1.6 db).

Sine waves at frequencies of 400 and 1000cps ±5%. Percent modulation continuouslyadjustable from zero to 95% at output levelsup to a dbm •.5 ';clf' Y'Mj r:.t!. (le'Trel/!..4 to 2:5 volt rms signal required. Percentmodulation continuously adjustable from a to95% at output levels of a dbm and below formodulating frequencies from 100 cps to above20, 000 cps.

Indicated by direct-reading panel meter accu­rate to ±10%.

Less than 5% at 30% modulation for frequenciesfrom 100 to 5000 cps. Less than 10% at 50%modulation.

20, 000 ohms shunted by 50 micromicrofarads.5#

Positive~volt peak pulse required. Com­bined rise and decay time of r-f output pulseless than 4 microseconds from 40 mc to220 mc; less than 1 microsecond from 220 to420 megacycles. Residual level at least 20db below 0.5 peak pulse output.

50,000 ohms shunted by 40 micromicrofarads.

Frequency drift less than 0.005% over a 10minute interval after initial instrument warm-up.

Better than to. 1% after initial instrumentwarm-up.

Less than 1,000 cycles at 50% amplitude modula­tion for RF output frequencies above 100 mc andless than 0.001% at RF output frequencies below100 mc.

Negligible; permits receiver sensi tivi ty measure­ments down to at least O. 1 microvolt.

-4-

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SECTION II

INSTALLA TION AND OPERATION

2-1 INTRODUCTORY

This section contains instructions for installing and operating theModel 608D Signal Generator 0 The infortnation contained in thissection is as follows:

2 -2 INSTALLATION

The Model 608D operates frotn a notninal 115/230-volt» 50 to 400cps single-phase power source o If the equiptnent is to be operatedfrotn a 230-volt source» the power transfortner pritnary windingtnust be reconnected as indicated on the schetnatic diagratn o Thepower cord supplied for connecting the generator to the powersource is equipped wi th a tnotor -base connector and contains threeconductors. The third conductor projects frotn the cord at eachend in the fortn of a green pigtail lead. This lead is for ground­ing the signal generator chassis to an external ground. To groundthe signal generator chassis connect one pigtail lead under one ofthe tnounting screws for the tnotor base connector on the instru­tnent chassis o Connect the other pigtail lead to the a-c outlettnounting boxo

InstallationOperating Controls» Dials. and TertninalsTurning on the EquiptnentContinuous Wave OperationInternal Sine Wave ModulationExternal Sine Wave ModulationPulse ModulationCrystal-Controlled Beat-Frequency CalibratorSignal Generator Loading Considerations

2 -22 -32-42-52-62-72-82-9

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2 -3 OPERATING CONTROLS. DIALS» AND TERMINALS

The front panel operating controls» dials» and tertninals for the608D are listed with their functions in Table 1 and are shown inFig o 2 0 A sitnplified block diagratn showing which circuits areaffected by various front panel controls is shown in Fig o 3 0

i

2-4 TURNING ON THE EQUIPMENT

CAUTION

Do not obstruct the ventilating louvers on thesides of the instrument cabinet. Safe opera­ting temperature depends on free air flowthrough these louvers.

To place the signal generator into operation, proceed as follows:

a. Locate the signal generator near a 115 -volt a -c powersource,

b. With power switch in "off" position, connect the powercord to the signal generator and to the power source.

._> c. Place the MOD. SELECTOR in the CW position and theOUTPUT LEVEL control to near maximum. Other con­trols may be set in any posi tion before turning generatoron.

f. Allow equipment to heat for 5 minutes before use. Ifgreatest frequency stability is required, allow equipmentto heat for 45 minutes.

d. Turn power switch to the ON position. The POWER pilotlamp should indicate that power is applied to all circuitsof the signal generator. '"o

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Controls and TerminalsTable 1.

e. After approximately I-minute warm-up, adjust the AMP.TRIMMER for maximum reading and OUTPUT LEVELcontrol to obtain a SET LEVEL reading on the front panelOUTPUT VOLTS meter.

Ref. No.Fig. l. Designation Function

1 Power Receptacle Receives power. from cordsupplied. For use on 115-volt, 50 to 400 cycle, single-phase, a-c source.

-6-

Table 1. (Continued)

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2 DC 0.25 AMP (fuse) Protects the internal d~c

power supply against shortcircui ts in the ins trument.

3 AC 3 AMP (fuse) Protects power source andinstrument against shortcircuits.

4 Power Switch In the ON position all cir-cuits of the signal genera-tor are energized.

5 POWER (pilot Pilot lamp that indicateslamp) when main circuits are

energized.

6 MOD. SELECTOR Prepares circuits for de-( switch) sired type of modulation.

7 FREQUENCY Selec ts frequency range toRANGE (switch) be used and positions the

range pointer on the MEGA-CYCLES dial.

8 FREQUENCY Selects output frequency inCONTROL combination with FREQUENCY

RANGE switch.

9 MEGACYCLES Indicates the frequency of(dial) the r~f output signal directly

in megacycles.

10 AMP. TRIMMER Tunes r -f power amplifier(control) circuit to track with oscillator

for maximum output as indi-cated on output meter.

11 OUTPUT LEVEL Adjusts the r -f power level(control) existing at input to output

a ttenuator.

-7-

Fig. 2. Model 608D Signal Generator Front Panel Controls

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Table 1.

Dc signation

OUTPUT VOLTS ­DBM (tlleter)

Output Attenuator(control)

RF OUTPUT(jack)

XTAL CAL, OUT­PUT (connector)

XTAL CAL~ GAIN(control)

EXT, MOD(jack)

MOD. LEVEL( control)

PER CENT MODU­LATION (tlleter)

ZERO

EXT. PULSE(jack)

CALIBRA TIONADJUSTMENT

-9 -

Function

Indicates r -f power levelexisting at input to out­put attenuator.

Selects and indicates ther-f output level in tllicro­volts, tllillivolts, anddecibels.

Output connector for 1'-'

output signal (SeeCAUTION).

Output connector to con­nect earphones to crys­tal calibrator.

Adjusts loudness of beatfrequency signal obtainedfrotll XTAL CAL. OUT­PUT jack.

Receives sine wave frotllexternal source for tllod­ulation of r -f output sig­nal.

Adjusts tllodulation per­centage to desired valueas indicated on tllodula­tion tlleter.

Indicates the percentagetllodulation of the r-foutput signal.

Electrically sets the tllodu­lation tlleter to zero withins trutllent in operationwi th no tllodulation applied.

Receives pulses frotll ex­ternal source for tllodula­tion of the r -f output signal.

Positions window hail lineto frequency dial.

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CAUTION

Do not connect any source of r-f or d-c powerto the RF OUTPUT jack on the Model 608DSignal Generator. To do so will burn out theitnpedance tnatching network in the output at­tenuator and no output will be obtained.Special care tnust be taken when working with,. transceiver" type equiptnents, such as VHFaircraft equiptnent, to insure that the trans­tnitter retnains inoperative while the signalgenerator is connected to the equiptnentantenna.

NOTE

For protection to the output attenuator on theModel 608D Signal Generator, a special fuse­holder is available for connection to the RFOUTPUT connector. When using the signalgenerator for any application where there isthe possibEity of voltage being applied to theRF OUTPUT jack, this fuse tnay be used be­tween the output jack and the test cable con­necting the signal generator to the externalequiptnent.

2 -.1; CONTINUOUS WAVE OPERATION

General

For CW operation the 608D supplies a continuous wave output sig­nal with less than 1% hartnonic or spurious signals and with lessthan 0.1% incidental atnplitude tnodulation. Over 1 tnilliwatt ofpower can be obtained acros s an external 50 -ohtn load with theoutput level directly indicated to an accuracy of better than ±1 dbfor all types of operation (see paragraph 2-10). When set for CWoperation, the MOD. LEVEL and XTAL CAL, GAIN controls areinoperative and tnay be set to any position. The PERCENT MODU­LATION tneter, however, tnonitors the output signal during alltypes of operation and tnay give tnotnentary fluctuations resultingfrOtn switching transients.

-11-

Step-by-Step Procedure for Obtaining CW Operation

a. Following the" turning on" procedure described above, setthe MOD SELECTOR to CWo

b. Select the desired band of frequencies with the FREQUENCYRANGE selector.

c. Set the MEGACYCLES dial to the desired frequency.

d. Set the OUTPUT LEVEL control to near m.axim.Ulu.

e. Adjust the AMP, TRIMMER for m.axim.um. output as indi­cated on OUTPUT VOLTS m.eter.

f. Connect the external load to the RF OUTPUT jack on thesignal generator. (See preceding CAUTION.)

g. Set the OUTPUT LEVEL control to obtain a reading atSET LEVEL on the OUTPUT VOLTS m.eter.

h. Set the output attenuator for the desired output level asread directly from. the output attenuator dial.

2 -6 INTERNAL SINE WAVE MODULATION

General

For internal sine wave m.odulation of the r-f output signal, the608D supplies the sam.e quality r-f signal as is obtained for CWoperation and which m.ay be m.odulated by either 400 - or 1000-cycle internally generated sine waves selected by the MOD. SELEC­TOR switch, The m.odulating frequencies are accurate to wi thin±10%, and evelope distortion of the m.odulated carrier is less than5% for m.odulation percentages to 30%. The percent m.odulationis continuously adjustable from. 0 to 95% by the MOD. LEVELcontrol and is read directly from. the PERCENT MODULATIONm.eter to within ±10% of the m.eter reading from. 30 to95%. Inci­dental frequency m.odulation resulting from. am.plitude m.odulationof the output signal is held extrem.ely low~ being less than 1000cycles for reasonable m.odulation percentages. For m.odulationpercentages below 50%, the frequency m.odulation index will notexceed 1. O. Output frequency and power level are set in thesam.e m.anner as for CW operation except that the MOD, SELEC­TOR is set to 400 or 1000.

-12-

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Step~by-Step Procedure for Obtaining Internal Modulation

a. Follow complete step-by-step procedure for obtaining CWoperation.

b. Set the MOD SELECTOR to 400 or 1000 as desired.

c. Set the MOD_ LEVEL :::c -etrol for desired degree of modu­lation as indicated on the PERCENT MODULATION meter.

d. Subsequent changes may be made in the frequency dial andoutput attenuator settings while instrument is being operatedwi th modula tion.

NOTE

It may be noticed that ~7hen the percentmodulation is increased to very highlevels there will be a resulting increasein the reading of the OUTPUT VOLTSmeter. The OUTPUT LEVEL controlshould be reset to maintain a readingat SET LEVEL on the OUTPUT VOLTSmeter.

2 -7 EXTERNAL SINE WAVE MODULA TION

General

An external signal source generating frequencies from 20 to above100,000 cycles per second with an amplitude of approximately. 5volt may be used to modulate the r -f output signal from the signalgenerator. The modulation is of the same high quali ty as thatobtained with internal modulation. The modulating signal is ap­plied through an appropriate cable to the EXT MOD. jack on thefront panel. The degree of modulation is continuously adjustableby means of the MOD_ LEVEL control and is indicated directly onthe front panel PERCENT MODULATION meter. Being a peakreading device, the modulation meter also indicates the modula­tion percentage of complex waveforms (square waves, sawtoothwaves, etc.) that are applied to the EXT. MOD, jack. The inputimpedance at the EXT, MOD jack is approximately 20,000 ohms.

Step-by-Step Procedure for Obtaining External Modulation

a, Follow complete step-by-step procedure for obtaining CWoperation.

-13-

b. Set MOD, SELECTOR to EXT, MOD. position.

c. Connect modulating source to EXT. MOD, jack.

d. Set MOD. LEVEL control for desired degree of modulationas read on the PERCENT MODULATION meter.

e. Subsequent changes may be made in frequency dial and out­put attenuator settings while the instrument is being opera­ted wi th modulation.

NOTE

It may be noticed that when the percentmodulation is increased to very highlevels there will be a resulting increasein the reading of the OUTPUT VOLTSmeter. The OUTPUT LEVEL controlshould be reset to maintain a reading atSET LEVEL on the OUTPUT VOLTSmeter.

2 -8 PULSE MODULATION

General

An external pulser generating positive pulses above 5 volts in am­plitude may be used to modulate the r-f output signal from the 608DSignal Generator, The resultant r -f output pulse from the signalgenerator is of good quality at r-f frequencies above 100 mega­cycles. is free of transients. and has low residual signal betweenpulses. For pulse operation the signal generator produces essen­tially no r-f output signal until an external positive pulse is appliedto the EXT, PULSE jack. The amplitude of the modulation pulseis not adjustable by the MOD. LEVEL control; however, the indi­cations on the PERCENT MODULATION meter cannot be used withsignals supplied to the EXT. PULSE jack. Any pulse above 5 voltsamplitude will 100% modulate the r-f output signal, the peak levelof the r-f pulse being within 1 db of the CW level established bythe same settings of the OUTPUT LEVEL control and the outputattenuator.

Step-by-Step Procedure for Obtaining Pulse-Modulated Output

a. Follow complete step-by-step procedure for obtaining CWoperation.

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c. Connect modulating source to EXT, PULSE jack on frontpanel.

2 -9 CR YSTAL -CONTROLLED BEAT-FREQUENCY CALIBRATOR

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The frequency (MEGACYCLES) dial in the 608D Signal Generatoris calibrated to be accurate within 1. 0%. To obtain higher ac­curacy, a crystal-con trolled calibrator has been included whichprovides the operator with a means of setting the MEGACYCLESdial calibration II on frequency" at any multiple of S megacyclesover the entire frequency range of the signal generator. Basically,the calibrator provides a S-megacycle signal accurate to ±O. 01%which, by heterodyning with the output frequency, produces abeat-frequency check point at every integral multiple of S mega­cycles. These check points appea.r as audible beats which can beheard by connecting a common headset to the XTAL., C~_L. OUT­PUT jack, with a volume control (XTAL CAL, GAIN) provided foradjusting the sound leveL An adjustment (knurled knob left ofMEGACYCLES dial) is provided which adjusts the position of theindex window a small amount each side of center and is used toset the MEGACYCLES dial lion frequency" at the selected checkpoint. For best accuracy the MEGACYCLES dial should be setlion frequency" on a calibration line nearest to the frequency tobe used.

SIGNAL GENERA TOR LOADING CONSIDERA TIONS

When using the Model 608D, the external load connected to theinstrument should be SO ohms resistive for best accuracy of in­dicated output power. The output attenuator dial has been cali­brated by using a "flat" load of SO ohms. The internal impedanceof the generator is sufficiently close to SO ohms so that in theworst case a VSWR of only 1.2 (SWR of 1. 6 db) exists when thegenerator is compared wi th 50 ohms. Error in power level indi­cation with this magnitude of VSWR will have no important effecton the accuracy of the output attenuator dial. However. if thevalue of the load is not known and if best accuracy in measure­ments is desired, it is necessary that the standing wave ratio inthe line to the load be minimi:~ed.

Table 2 shows the calculated power loss when the load on the sig­nal genera tor caus es a voltage standing ra ti 0 of the magni tudeshown. The VSWR values shown _re a comparison between a loadand a SO-ohm transmission line. The minimum loss figures arebased on a mismatch of 1.2 VSWR between the signal generator

-15-

and transm.ission line. Mism.atches causing the voltage standingwave ratios given in the left-hand colum.n will give power lossessom.ewhere between the lim.its shown in the rem.aining two colum.ns.The m.axim.um. loss shown is the total loss from. the m.axim.um.power available from. the generator for a given setting of the out­put attenuator and includes the possible generator VSWR of 1. 2.The data does not allow for losses in the transm.ission line to theload, for in m.ost cases such losses are sufficiently sm.all so thatthey are not of im.portance.

It will be seen that when the load is m.atched to the transm.issionline (VSWR ': 1.0) the loss from. the m.axim.um. power availablefrom. the signal generator is approxim.ately 0.06 db in the worstcase. Although the losses as shown in db do not consist of largenum.erical values, it should be noted that they m.ay represent aconsiderable change in the voltage calibration of the output attenu­ator dial so far as the voltage im.pressed across the external loadis concerned.

Table 2

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VSWR Min. Max.in 50-ohm. Power Power

Line Loss Loss

1.0 .06 db .06 db1.5 .08 db .37 db2.0 .3 db .85 db2.5 . 6 db 1.3 db3.0 .9 db 1.7 db4.0 1 • 5 db 2.4 db5.0 2 • db 3 . 1 db

In m.ost cases when m.aking m.easurem.ents on receivers designedto work from. a 50 -ohm. line and antenna. the s tanding wave ratioin the line from. the signal generator to the receiver is not signifi­cant. The reason for this is that any power reflected from. thereceiver back towards the generator represents a deficiency inreceiver design, and the am.ount of power lost in such cases isconsidered as a loss subtractive from. the gain of the receiver. Asom.etim.es overlooked factor which contributes error in high­frequency m.easurem.ents is the im.proper as sem.bly of coaxialconnectors. A standing wave ratio of several db with attendanterror can often be attributed to this cause.

-16-

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2-11 FINE FREQ. ADJUST. CONTROL

Model 608D Signal Generators with serials 104 and above areequipped with a short range incremental tuning device for makingextremely small changes in the output signal frequency. Thefine frequency tuner is operated from the front panel by a smallknob to the left of the main FREQ. control knob. This controladds a very small capacity to the existing capacity in the oscil­lator tank; the change occurring over 180 0 rotation of the knob.When the dot points to the left, the vernier capacity is maximum;when the dot points to the right, the capacity is minimum. Themain frequency dial calibration is most accurate when the dot onthe knob is alligned with the dot on the front panel,

When the signal generator is operated at the high ends of thefrequency ranges and when the finest possible frequency controlis required, adjust the main frequency control very closely tothe desired frequency with the vernier set slightly above mini­mum capacity, i. e., dot pointing to right; then adjus t the verniercontrol for the exact desired frequency. When operating at thelow ends of the frequency ranges the effectiveness of the vernieris decreased and must be used at near maximum capacity.

The accompanying figure shows the vernier device as it ismounted within the oscillator tuning compartment of the r-fgenerator assembly, The fine frequency tuner consists of asmall metal disk mounted off center at the end of a bakelitecontrol shaft. The shaft is mounted level wi th the oscillatortuning capaci tor about 1/2 -inch away. As the shaft is turned,the disk moves closer or farther from the tuning capaci tor toincrease and decrease the capacity in the tuned circuit,

-16a-

MAIN TUNING CAPACITOR

f"INE TUNING CONTROL

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SECTION III

THEOR Y OF OPERATION

3-1 GENERAL

The electrical circuits of the Model 608D Signal Generator aredivided into the sections shown in the block diagram in Figure 4,plus a power supply which is not shown. Briefly, the operationof the various sections is as follows:

a. The radio frequency oscillator generates the r -f signalwhich is fed through a buffer and power amplifier to theoutput jack of the signal generator. The oscillator is ofthe Colpitts type and provides a continuously variable sinewave signal of high stability.

b. The buffer isolates the oscillator from the power amplifierand minimizes interaction between the two circuits.

c. The radio frequency power amplifier receives both the r-fand modulation signals and amplifies the r -f energy forapplication to the output attenuator. The r-f amplifier alsoreceives variable bias from the modulator which permitsadjustment of the power level fed to the output attenuator.

d. The output power monitor samples the r=f energy fed tothe output attenuator and indicates the power and voltagelevel on a front panel meter.

e. The output attenuator obtains monitored r-f energy fromthe power amplifier, applies the selected degree of attenua­tion, and conducts the energy to the front panel output jack.

f. The beat frequency calibrator generates harmonics of the5 mc signal from the crys tal and mixes these harmonicswith r-f energy coupled from the r-f amplifier. The re­sultant beat frequency signal is amplified and fed to thefront panel earphone jack.

g. The internal modulation oscillator generates either a 400or 1000 cycle -per -second sine wave for application to themodulation system.

h. The modulator receives all signals for application to ther -f power amplifier and also supplies variable bias to ther-f amplifier for control of the r-f output level.

-17-

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i. The modulation-measuring circuits receive detected mod­ulation from the r-f power monitor. amplify and rectify it,and indicate the modulation percentage directly on a frontpanel meter,

RADIO FREQUENCY OSCILLATOR

The radio frequency oscillator generates a sine wave signal from10 to 420 megacycles in five frequency bands, each band havingapproximately a 2: 1 frequency range. A type 5675 "pencil" triodetube is used in a Colpitts circuit tuned by a precision split-statorcapacitor (plate meshing type) and five separate r -f transformers,Ll through L5. The tuning capacitor, which is specially construc­ted for high stability and resetability, consists of two stator sec­tions connecting to the grid and plate of the oscillator tube and afloating rotor which meshes equally between the two stators. Thetuning capacitor assembly, mounted inside and near the top of thetuning compartment in the r-f generator housing, is driven by aball bearing mounted worm drive through the top of the housingcasting.

The tuned coils consist of precision-wound, plated wire on 5/8­inch diameter ceramic forms on the As B, and C bands and ofsilver-plated, Nilvar loops on the D and E bands. The five in­ductors are mounted on a revolving turret actuated by the FRE­QUENCY RANGE selector. As the tu:':'ret is rotated, the desiredcoil is positioned in the tuned circuit just below the oscillator tubeand tuning capacitor, connections being made through large silver­plated contacts mounted directly on the bottoms of the two statorsof the tuning capacitor, Both ends of the tuning inductor and capaci­tor are at r-f and d-c potential, with no part of this circuitgrounded.

The oscillator tube, V6, is operated across the -165-volt and+225-volt supplies with considerable series resistance to limitthe maximum plate current that can flow, The plate is series-fed through a 3000-ohm resistor, R45, which also serves to iso­late the tuned circuit from r-f ground at C15. while the cathodeis returned to -165 volts through R42 and R43, Cathode by-passcapacitor C25 is actually part of the tube mounting plate and isnot visible when the plate is in posi tion. R42 prevents resonancein the cathode lead; R43 in conjunction with R45 limits the maxi­mum plate current that can flow through v6. Bias for the controlgrid is obtained across grid leak resistor R44. which under usualcondi tions develops approximately 70 volts of bias, C 16 couplesthe tuning coil to the grid, the drive being determined by the ratioof grid-plate to grid-cathode impedance. These impedances con­sist partly of inter -electrode capacity shown as dotted components

-19 -

in the partial schematic diagram, and largely of lumped constantsin the tuned circuit. The grid-plate capacity is shunted by thetuned circuit and a small trimmer capacitor C18, while the grid­cathode capacity is shunted by trimmer capacitor C59. Cl8 setsthe minimum capacity of the tuned circuit and is used to adjust thehigh frequency limi t of all bands when the oscillator tube is re­placed. C59 is an additional adjustment usually set for minimumcapacity and requiring no readjustment. 'This capacitor has minoreffect on the grid drive at the high frequency ends of the bands andis usually set for maximum drive. The inductances of the tunedinductors is variable over a small range by adjusting a singleshorting turn on each coil for the A, B, and C bands and by adjust­ing the size of the single loops for the D and E bands. These ad­justments are used at the factory to set the low frequency limitof each frequency band.

Heater voltage for the oscillator tube is obtained from a multivi­brator operating on regulated voltage which supplies very stableheater power. All power to the oscillator tube is brought throughthe housing by special filters having very high attenuation of radiofrequencies to prevent conduction of the r-f energy outside f.~

instrument. The tuned circuits for the oscillator are located in alower front compartment, t:le other circuits in a tube compartmentabove. An inside view of the r-f generator assembly is shown inFigure 14. The oscillator tube is mounted through the top of thetuning compartment so that the grid and plate elements projectthrough the top plate into the tuning compartr:-1ent, whi:. ~ ~' ... '.""I.eaterand cathode elements remain abu\l'c the top plate. Mounting facili­ties are contained in the upper compartment, and the tube may bereplaced from the upper compartment without entering the tuningcompartment.

3-3 RADIO FREQUENCY BUFFER

The loosely-coupled secondary winding on each of the oscillatorcoils couples r -f energy fr om the oscillator through a coaxial cableto the buffer stage located in the tube compartment in the top ofthe r f cienerator housing. The buffer tube, V7. is a tYr~ 6BC4mini2.l;ure triode connected as an untuned, grounded-grid amplifierand serves to isolate the oscillator circuit from the effects of themodulation signal at the ca thode of the power amplifier. The useof the buffer reduces incidental frequency modulation to an extremelysmall value.

Although the buffer tube V7 utilizes a large cathode resistor (R116,7500 ohms), it operates with practically zero bias and relativelyhigh plate current. R116 holds plate current constant for a widerange of tube characteristics and in conjunction with R47, a dropP'.ng

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resistor in the plate supply lead~ serves to limit plate current tosafe values. Resistors R46. RI08. RI09. RHO. and RIl2. whichare mounted on the coils for each band. damp unwanted resonancein the cathode lead. Resistors RIll and Rll3 shunting the A andB band coupling coils limit the somewhat greater r=f drive fromthese coils. The plate of the buffer is coupled to the cathode ofthe r-f amplifier through a wide-band. coupling network consistingof coil L8 with damping resistor Rl3. series coil L9 with blockingcapacitor C56. and shunt peaking coils LID and LIL Resistorsshunting the peaking coil are used as he forms for the windings.The resistor values are selected to damp the resonant peaks ofthe coils.

RADIO FREQUENCY POWER AMPLIFIER

The radio frequency power amplifier. V • amplifie t e r-f energyreceived from the buffer for application to the r=f output attenuator.The circuit consists of a 5876 "pencil" triode conn cted as a grounded­grid. cathode - modulated amplifier. The plat circuit of the ampli­fier is tuned in the same manner as the oscillator. ith a similarsplit-stator capacitor and five untapped coils mounted on a revolv=ing turret. The amplifier tuning capaci tor is ganged with the os­ciIlator capacitor by a double-ended worm drive. The amplifiercapacitor is provided with a me hanical linkage. controlled fromthe front pa el. to shift the rotor pates from their normal track-ing position ith res ct to t 0 ciilator. This control allowsthe amplifier tuning to be trim d for rna imum outp t at all fre­quencies •

The coil mounting turret is also gang d wit that of the 0 cillator.Tuned oils are wound with copp r wire on tefl n fo ms. and thecoil in use is so located to be inductively coupl d to tb. outputattenuator probe.

The power amplifier tube is operated aero s the - 65 and +225 ~

volt supplies. The plat i seri fed from e 225 -volt supplythrough decoupling filter R57 and C 3. Th c thode i returnedthrough a portion of the wide-band coupling filter and re i torsR35 and R36 to the -165-volt up lYe R36 matches the higher im­pedance of the cathode circuit of V5 to the ower imp dance of thecathode circuit of V8, while R35 is the cathod bias-dev lopingresistor. R35 is also the cathode load r sistor for control tubeV5. and the bias voltage developed across R35 is largely controlledby the current established in V5. The modulating signal is alsodeveloped across R35 and with th bi s voltage is fed to the cathodeof V8. Crystal diode CR7. connected bet een the cathode returncircuit and ground. limits the 10 st pote ti I to which the cathodecan be driven. This arrangement protects V8 from the effects of

-21-

3-5

any negative switching transients which might be applied to itscathode. The plate tank is tuned by C 17B. C32, a small trimmercapacitor across C17B, sets the minimum capacity and is prov;dedfor adjusting the tracking of the highest frequency band so thatminimum operation of the AMP TRIMMER control is required.The inductances of the tuned coils can be adjusted over a smallrange by means of metal sleeves between the cores and coils onthe B, C, and D bands and by altering the winding shape and sizeon the A and E bands. These adjustments are set at the factoryto track the low frequency end of each band with the frequency ofthe oscillator.

Heater supply voltage for the r -f amplifier, buffer and oscillatoris obtained from the regulated heater s'lpply multivibrator . FilterFL9 in the heater circui t reduces incidental frequency modulationby preventing leakage of me IJT1.:ating signals between the heatersof the oscillator and amplifier tubes. The tuned circuits of ther -f amplifier are contained in the rear compartment of the r-fgenerator housing. The other amplifier circuits are located in thecompartment above. The amplifier tube is mounted through thetop of the tuning compartment so that the plate element projectsthrough the top plate into the tuning compartment. The heater andcathode elements are in the upper compartment and the tube maybe replaced without entering the tuning compartment.

OUTPUT A TTENUATOR AND R -F POWER MONITOR

To extract power from the r=f power amplifier a piston attenuatoris used. The housing for the attenuator projects through the rearof the r=f generator housing and terminates, open-ended, closeto the r-f amplifier plate circuit inductor. A single=turn, pickuploop at the end of the attenuator probe couples energy to an im­pedance-matching network, C37, R58, and R59, mounted on theface of the probe and through a section of double -shielded coaxialcable to the RF OUTPUT jack. Adjustable capacitor C37 is ac­tually a movable slug in the probe body. It allows minor adjust­ment of the internal impedance of the generator so that a minimumstanding wave ratio is obtained when the output jack is terminatedin a 50-ohm load.

The r -f power level which is fed to the attenuator is sampled andcontinuously monitored by an antenna (two parallel wires crossingthe open end of the attenuator housing) connected to a small de­tector assembly mounted under the housing inside the r-f amplifiertuning compartment. This power level is indicated in both voltsand decibels, over a limited range, on the front panel power levelmeter. A calibration mark on the meter marked SET LEVELes tablishes a correct amount of power fed into the attenuator

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housing for direct reading of the output attenuator dial calibrations.

Radio frequency energy is coupled from the power monitoringantenna to a detector through LI7 t a small coil used to adjust thefrequency response of the detector circuit, Crystal diode CR2with return resistor R60 rectifies the radio frequency energy andproduces a d-c voltage equal to half the peak-to-peak r-f voltage.C38 and filter FL8 remove the remaining r-f component and couplethe d-c voltage to a compensating network, CR3 and R61. R119flattens the frequency respons e of the circuit. FL8 is speciallydesigned to attenuate all radio frequencies above approximately3 megacycles and to pass all frequencies below that frequency withlittle or no attenuation. CR3 corrects for non-linearities in de­tector CR2 when the r -f signal level is low and detection takesplace in the non-linear region of the diode. The degree of com­pensation is set by potentiometer R6I and is adjusted to obtainaccurate down-scale readings on the front panel power level meter.Ml is calibrated to indicate the rms value of the r -f output signal.Potentiometer R62 adjusts the sensitivity of the meter and is setat the factory wi th accurate vhf power measuring equipment.

XTAL (BEAT FREQUENCY) CALIBRATOR

The calibrator consists of a crystal-controlled oscillator anddetector located in the r -f ampUrie:r tuning compartment and an80 db resistance-coupled amplifier located on the right side chassisof the ins trument,

The crystal oscillator uses a type 6AU6 miniature pentode connectedas an electron coupled oscillator, having both the plate and screencircuits tuned to the crystal frequency of 5 megacycles. Limitedadjustment of the crystal frequency is provided by trimmer C23connected across the crys tal. The calibrator signal is coupledfrom the plate of the oscillator through blocking capaci tor C24 tothe cathode of mixing diode CRl, The signal from the r-f poweramplifier is inductively coupled to the anode of the mixing diodeby running the anode lead of the diode close to the r -f amplifiercircuits. Harmonics of the calibrator are generated in the crys-tal and mixed with the r-f signal to produce beat frequency signalsacross R50.

Beat frequency signals from the mixing diode are taken throughr-f filter FL7 in the r-f generator housing to a conventional three­stage resistance-coupled amplifier consisting of VIO and Vll.high··f.L twin triodes connected in cascade and located on the rearchassis. Only one half of VIO is used. the remaining half beinggrounded. Due to the extremely high gain approximately 80 db)of the amplifier, grounding of the input circuits is extremely

-23-

c:itical. The load resistor (R50) for mixer diode CRl and thecathode an::! grid return resistor (R51) for VIa are not groundednear the tube socket but are connected to the shield of the inputcable which in turn is grounded at the r-f generator housing, asshown on the schematic diagram. Potentiometer R56 in the gridcircui t of the last amplifier stage controls the volume of the beatfrequency output signal. The signal from output stage is coupledthrough a 600 -ohm line matching transformer T3 to the front panelEXT CAL. OUTPUT jack.

3 -7 MODULATOR SECTION

The purpose of the modulator section is threefold: to generate 400­and I 000 -cycle sine waves for internal modulation of the generator;to amplify all modulation signals for application to the r-f poweramplifier; to control the power level obtained from the r -f ampli­Her for all types of operation by varying the bias on the r-f ampli­fier tube. The modulator consists of a resistance-tuned oscillator,V2, a limiter and single-stage video amplifier, VI and V3, and acathode follower output stage and output level control tube, V4 andV5. The modulator circuits are located along the upper portionof the right side chassis; the oscillator on the bottom portion.

The modulation oscillator is a resistance-tuned sine wave genera­tor of the Wein Bridge type. Basically, the circuit consists of atwo-stage resistance-coupled amplifier which is caused to oscil­late by the use of a frequency-selective positive feedback circuit.At the resonant frequency there is no phase shift in the positivefeedback circuit, so that a voltage of the resonant frequency on thegrid of the first tube is reinforced by the output of the second tubeand oscillation occurs. The two different frequencies of operationare obtained by switching two different sets of resistors~ R3 - R5and R4 - R6, into the positive feedback network when the MOD.SELECTOR is turned from 400'\ to 1000'\. Precision resistorshaving good stability are used in the tuned circuit. Capacitors C2,C3. and C4 comprise the remainder of the tuned circuit. In ad­dition to the posi tive feedback network~ a negative feedback circui tis also used to stabilize the oscillator. reduce distortion, and tomaintain a cons tant output level. This circuit consists of a 3 -wattlamp, Il~ used as a thermal resistance element having a positivetemperature coefficient, composition resistor R8 and amplitudeadjusting potentiometer R 7. The high posi tive temperature co­efficient of the lamp provides automatic ampli tude control of thesignal, for if the amplitude of oscillation tends to increase. thecurrent through the lamp tends to increase, thereby increasing thelamp's resistance. Consequently, the negative feedback tends toincrease and amplitude of oscillation is maintained constant. Theamplifier portion consists of two medium-..... triodes~ V2A and B,

-24-

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in a conventional resistance-coupled circuit with the output volt­age being obtained from the cathode of the second stage. Althoughheater voltage is applied to the oscillator at all times the instru­ment is in operation, plate voltage is applied to V2 only when theMOD, SELECTOR switch is in the 400- or 1000-cycle position.

The sine wave signal from the modulation oscillator or from anexternal signal source is cou~ ~ed through the MOD. LEVEL con­trol to the limiter tube VI, a 5670 twin triode; then to video am­plifier V3, a type 6CL6 pentode. The purpose of VI is to limitthe peak amplit\.1de of modulating pulses, since for pulse modula­tion the input signal is fed directly to the grid of the limitingamplifier without passing through the MOD, LEVEL control. Thelimi ting action of V 1 begins at approximately +2 volts peak whichis considerably more than that required for 100% modulation ofthe output signaL Consequently, signals producing less than 100%modulation pass through the limi ter unchanged, Limiting effect­ively squares the top of an incoming positive waveform aboveapproximately 2 volts without affecting its rise and fall or intro­ducing transients. The uninverted signal from ampIi tude limiterVI is then an... ~)l.i.fied approximately 18 db by V3, a resistance­coupled 6CL6 pentode voltage amplifier, and coupled to outputcathode follower V4.

From the limiter and amplifier, the modulating signal is fed tooutput cathode follower V4. a triode-connected type 6CL6 pentode.For sine wave modulation the signal from the cathode of V4 iscoupled through switches SlE and SlF to the grid of the outputlevel control tube V5 and superimposed on the variable bias volt­age. The cathodes of both V5 and the r-f power amplifier V8 areconnected together and returned to the -1 ': _ volt supply throughresistor R35. Any signal placed on the grid of V5 is thereforedirectly coupled from the cathode of V5 to the cathode of the r-fpower amplifier V8, The d-c voltage level established at thecathodes of the two tubes is determined largely by the currentflowing in V5. The current in V5 is controlled by the dual poten­tiometer voltage divider, R34. R37, and R40 in the grid circuit.The cathode bias for V8, and cons equently the r -f output power.is varied by front panel output level potentiometer') R3 I! '. 'r'. R?-7R.

For pulse modulation the cathode of V4 is connected by the MOD,SELEC TOR swi tch directly to the cathode of V5, The additionalcurrent drawn by V4 through common cathode resistor R35 pro­duces a sufficiently high bias to cut off the r -f amplifier and re­duce the r-f output to zero, The modulating pulses are not appliedto the grid of V5, and it now serves only to control the peak levelof the r-f output pulse, Negative modulating pulses (the positiveinput pulse having been inverted in V3) a" ··11e grid of V4 cut offV4 and allow the cathode potential to return to the level set by V5

-25 -

which establishes an r-f output level equal to the CW level as in­dicated on the output level meter. An r -f output pulse having anenvelope shaped like the modulating pulse is then formed.

3 -8 MODULATION -MEASURING CIRCUITS

The modulation-measuring circuits in the 608D indicate any mod­ulation of the r-f output signal between 0 and 100% to an accuracyof ±10% or better. These circuits consist of a stabilized wide­band amplifier and a bridge -type metering circui t. The measuringcircuit reads the peak value of the rectified modulation signal andis accurate for all waveforms. The meter is calibrated to indi­cate the percent modulation of a given amount of r -f carrier power.The amount is established by SET LEVEL on the output level meterand is accurate for all settings of the output attenuator.

The circuit diagram for the stabilized amplifier, consists of twoconventional resistance-coupled type 6AH6 pentodes, V18 and V19.The circuit is stabilized by negative feedback and provides approxi­mately 22 db gain to approximately 2 megacycles. The feedbackloop covers both stages, the feedback signal being coupled fromthe plate of the second stage through dropping resistor R99 andblocking capacitor C55 to the cathode of the first stage. Thecircuit for the bridge consists of diode rectifier V20 and twin­triode V21, the two triodes constituting two legs of the meterbridge. With no modulation signal applied to the amplifier, thesteady-state d-c potential at the plate of amplifier V19 is coupledto the grids of both triodes of V21. With equal current flowing inthe two sides of the bridge, the bridge is balanced and the meterreads zero. Potentiometer Rl06 is a front panel zero adjustmentof the bridge that provides for variations in tube and componentvalues.

A modulation signal from amplifier Vl9 is rectified by diode V20,and the peak value of the rectified voltage is applied to the triodein one leg of the bridge, unbalancing the bridge and causing themeter to read upscale. The triode in the other leg of the bridgeis unaffected by the modulation signal as the signal is filtered outby resistor RIOI and by=pass capacitor C58. PotentiometerRI04 sets the sensitivity of the meter and is adjusted for correctcalibration of the meter.

3 =9 POWER SUPPLY

The power supply for the signal generator consists of two elec­tronically regulated high voltage supplies, one providing - 165volts d-c, the other providing +225 volts d-c, with the chassis at

-26-

0'o00

·tJ

~

C1'cext;cC0'

-.DooQCOo-.D=11:=

QCOo-.D 3-10

zero potential. Each regulator is supplied from a full-wave brid 5e­type selenium reet~"-l~r with a separate high voltage winding on thepower transformer. The power transformer also supplies a-cvoltage for all electron tube heaters except the r -f os cillator andpower amplifier. The primary winding of T 1 is divided into twoparts and may be operated in series for 230 -volt lines or in paral­lel for 115-volt lines. The output of each regulated supply isadjustable by screwdriver adjusted potentiometers R80 and R 71on the rear instrument chassis. The +225-volt supply uses the-165 supply for a reference voltage; consequently, a change in the-165 volts also affects the output from the 225 ~volt supply.

Since the two regulated power supplies are identical in operation,only the -165-volt supply will be discussed. V14, V15, and V16constitute the voltage regulator circuit for the -165-volt supply.V 15 is a cons tant-voltage tube which provides a reference biasfor voltage amplifier V 14. V 16A operates as the regulator tube(or variable resis tor) controlled by the voltage at the grid of V 14.If the regulated output from the ca.thode of v16A tends to increase,the voltage at the grid of V 14 tends to increase, causing V 14 todraw more current. This lowers the plate voltage of V 14 andconsequently the grid voltage of v16A. resulting in a greaterplate resistance for VI6A. The greater plate resistance causesa greater voltage drop across VI6A, instantaneously compensatingfor the increased voltage at its cathode and resulting in a sub­stantially constant voltage output.

If the regulated output tends to decrease, the reverse of the aboveaction occurs, also tending to maintain the cathode voltage con­stant. Ripple in the output voltage is coupled to the grid of V14by capacitor C44, while slower variations in the d-c level are fedto the grid of V14 through voltage divider R79, R80, and R8I.The bias for V14, and thus the output voltage level from VI6A. isdetermined by the setting of R80,

The operation of the +225-volt sUFPly is identical; but ::~ue to ad­ditional current required (approximately 150 m.a), three regulatortubes (VI3A and B, VI6B) m.ust be used in parallel. The referencevoltage for the +225 -volt supply is obtained directly from. the -165­volt supply.

HEATER SUPPLY MULTIVIBRATOR

To provide constant heater voltage to radio frequency tubes V6,V7, and V8, a free -running m.ultivibrator operating on the +225­volt regulated supply is utilized. The m.ultivibrator developssquare waves that are substantially constant in am.pli tude becausethe plate voltage excursion is lim.ited by the 225-volt supply and

-27-

the TnaxiTnuTn conductivity of the tube. The type 5687 has suffi­cient conductivity to cause the plate voltage to fall to approxiTnately25 volts during the negative half cycle. The Tnultivibrator, whichoperates without bias, is grid-plate coupled and produces syTn­Tnetrical waves. TransforTner T2 couples the output of the Tnulti­vibrator to heater circuits within the r-f generator housing. Po­tentioTneter R87 is used to adjust the plate voltage of V17 andthereby acts to control the applied filaTnent voltage for V6, V7,and V8. Resistors R84 and R85, in the grid circuit of the twotriodes, prevent grid loading of the opposi te plate circuits whilethe grid is in the positive part of its cycle; R83 and R86 are thegrid return resis tors.

-28-

(J)C1l1'1.....III.......

::jj:

C1'cext:cC0'

SECTION IV

MAINTENANCE

4-1 INTRODUCTION

Section IV contains instructions for preventive maintenance,trouble localization, tube replacement procedures, and internaladjustments in the Model 608D Signal Generator. To assist withservicing the signal generator, a trouble shooting chart and circuit­tracing block diagram are also included. At the end of this sec­tion will be found additional locating illustrations, tube socketvoltage and resistance diagrams, and the schematic diagram forthe complete equipment. The following information can be foundin this section:

-.!) 4-200 4-3q

4-4000 4-5-.!)

=II:: 4-64-7

I1l4-8>

0 4-9,Dro •

"tJ 4-10s:lroN. 4-110'.-c..... 4-12ro....

4-13I-lI1l 4-14U)

4-15ll)ll)

4-16'-.0' 4-17.-c'-.ll)

q000-.D

Cabinet RemovalPeriodic Checks and Routine CareLocalizing TroublePower Supply Trouble Shooting and AdjustmentSystem Analysis Check ChartReplacement of Electron TubesRadio Frequency Oscillator Tube ReplacementRadio Frequency Amplifier and Buffer Tube

ReplacementXtal Frequency Oscillator Tube or Crystal

ReplacementReplacement of Electron Tubes Within the Crystal

Power SuppliesAttenuator Probe ReplacementReplacement of Lamp IICalibration of the Percent Modulation MeterOutput Volts Meter Calibration and R-F

Power Moni tor ServiceRepairing the Calibrator OscillatorTrouble Shooting Chart

-29 -

CABINET RETAINING SCREWS

( CAPTIVE TYPE)

Fig. 5. Cabinet Rem.oval Diagram.

-30-

==II::0'o00boo0'

-.0ooQcoo-.0=II::

.....ell....I-l(j)

U)

Qcoo-.0

4-2 CABINET REMOVAL (Figure 5)

To remove the instrument chassis' from the cabinet, loosen thefour captive screws on the rear of the cabinet and pull the instru­ment from its cabinet by the guard-rail handles o The rear of theinstrument chassis is supported on steel rollers and should movefreely from the cabinet.

4-3 PERIODIC CHECKS AND ROUTINE CARE

Preventive Maintenance

Reasonable care in transporting, handling, and operating the 608DSignal Generator will help to prolong its useful life and minimizetrouble. No special checks are required other than a generalalertness for the effects of misuse, loose controls, condition ofcables and connectors, and possible damage that may be evidentin its general appearance. A limi ted but useful operational checkmay be performed without the use of external equipment by operat­ing the equipment as instructed in paragraph 2 -6, indications ofnormal operation being read from the two front panel meters. Ifthe equipment has been subjected to unusual conditions - excessivemoisture, dust, heat, vibration, etc. - it is suggested that theinstrument be removed from the cabinet and inspected for dirt ormoisture accumulation, loosened components, or any possiblesign of damage. Forced air under medium pressure is recom­mended for dusting and drying, although care must be taken notto vary the settings of the internal adjustment potentiometers andcapacitors during the process o When tightening nuts and screws,various degrees of pressure are required depending on the strengthof the material and weight which is supported. Avoid overtighten­ing o

Lubrication

The 608D is thoroughly lubricated at the factory, and it is not tobe expected that subsequent lubrication will be necessary duringthe first year of use. The gears in the r-f generator housing op­erate at slow speeds and transmit negligible power. Fully shieldedball bearings are used in many applications and require no sub­sequent attention. Ball bearings that are not fully shielded requireonly light machine oil. If cleaning and relubrication are neededafter prolonged use of the instrument, excessive dust accumulation,or drying of lubricant, reference to the following chart and Fig­ures 6 and 10 will assist with renewing the lubricants at variouspoints on the r-f generator assembly. The two worm gears usedin the tuning capacitor drive are lubricated with a mixture of 9parts of Lubriplate grease #2 and 1 part Molycote o All remaining

-31-

RF OSCCAPACITOR

DRIVE

MEGACYCLESDIAL HUB

RF AMPSLIDINGCOUPLER

RF AMPCAPACITOR

DRIVE

FREQ.DRIVE

AMPTRIMMER

FREQ.STOPGEAR

AMPTRIMMER

STOPMECHANISM

OSCWORMDRIVE

AMP TRIMMERDRIVE LINK

AMPTRIMMERTOGGLE NUT

AMPWORMDRIVE

AMPWORMDRIVESHAFT

S~& 0'oex>tJ

Fig. 6. R-F Tuner Drive MechanisYn

-32 -

=ll::0'oex>tJoo0'

sleeve bearings and rubbing surfaces - including the small pulleysused in the attenuator drive system - are lubricated with a lightsynthetic oil such as Shell Tonna oil G, The bakelite RANGESELECTOR drive shaft and the attenuator drive shaft - not shownin the illustration - require Lubriplate grease #2 where they enterthe r -f generator housing. In all cases, avoid overlubrication.

Lubrication Chart(See Figures 6 and 10)

.-.cd.....~

~U)

Oscillator and amplifierworm gears

AMP. TRIMMER stopmechanism

AMP. TRIMMER toggle nut

AMP. TRIMMER drive link

Amp. worm drive shaft

Amp. sliding coupler

Attenuator pulleys

Attenuator drive shaftfront panel bearing

Attenuator housing guideslot

4-4 LOCALIZING TROUBLE

Mixture of 90% Lubriplate #2and 10% Molycote

Light machine oil, such asShell Tonna oil G

Same as above

Same as above

Same as above

Same as above

Same as ab ove

Same as ab ove

Lubriplate #2

The first step in correcting any trouble which may occur in thesignal generator is to isolate the section of the equipment thatcauses the trouble. The various circuits of the 608D Signal Genera­tor occupy easily defined areas and offer very good circuit acces­sibility. The locations of the various sections are shown in Fig­ures 12, 13, and 14. Figures 15 and 16 will als 0 prove helpful inlocating circui ts within the r -f generator housing.

Trouble ordinarily occurs in only one section of an equipment atone time; therefore, it is usually necessary to correct only the onetrouble. Isolation of a circuit failure is best accomplished by con­sidering the basic sections shown in the block diagrams in Figures3 and 4. Careful determination of the nature of a trouble symptom

-33 -

usually leads to the section at fault. To aid in servicmg, a trouble­shooting chart that indicates certain possible specific troubles andtheir symptoms and a signal tracing blank diagram are included.In addition, tube socket voltage and resistance diagrams and theschematic diagram for the complete equipment are included at theend of this section.

4-5 POWER SUPPLY TROUBLE SHOOTING AND ADJUSTMENT

Table 3 systematically locates troubles in the power supply sec~

tion using a reliable 5,000 ohm/volt multimeter. The point atwhich a voltage and resistance is to be measured is listed in col­umn 1. A correct voltage reading obtained from the second columnindicates the particular circuit tested to be operating properly andmay be passed by. An incorrect or unstable voltage indicationshould be corrected as instructed in the service note in the lastcolumn. All voltages are measured from chassis ground. Whenpossible, use a variable line transformer to adjus t the line volt­age between 105 and 125 volts when measuring the power supplyvoltages. Marginal operation is quickly detected in this manner.as the regulated voltages should remain stable during such linevoltage changes. Refer to Fig. 17a at rear of manual.

Table 3. Power Supply Trouble Shooting Chart

Measure NormalVoltage At: Indication

1. Tl 6.3 volts(filament a-c rmswinding)

2. C45(across ter­minals)

-165 voltsd-c (regu­lated)

- 34-

Service Note

This voltage will read be­tween 6.2 and 6.3 volts rmswhen the line voltage is 115volts. A noticeably higheror lower voltage indicatesthat the line voltage is sig­nificantly more or less than115 volts.

This is a s table regulatedvoltage accurately adjustedby R80. If this voltage issignifican tly high. low, orerratic, check voltageacross V 15 which should bea steady 150 volts. Forexcessively high output.check V14; for too low output,

0'o00

.t:J

==II::0'o00t:lo

.00'

'"ooQcoo

'"=I;:

Qcoo

'"

Table 3. Power Supply Trouble Shooting Chart (Contd.)

Measure NormalVoltage At: Indication Service Note

check V 16A and the voltageapplied to V16A (260 vdc).A weak selenium rectifierCR6 which supplies low volt=age to the regulator willcause unstable operation ofthe regulator.

3. Resistor +225 volts This is a s table regulatedboard d-c (regu- voltage accurately adjusted(red leads) lated) by R71. If this voltage is

significantly high. checkV12; if too low. check Vl3and the voltage applied toVl3 (360 vdc). A weak sele-nium rectifier CR4 or CR5which supplies low voltageto the regulator will causeunstable operation of theregulator.

4. T2 7.6 volts This is stable square wave( Terminal 4) as read voltage that must be meas-

on average ured by an average readingresponding meter calibrated in rmsmeter cal- volts and is accurately ad-ibrated in justed by R87. This voltagerms volts. is applied only to the three

r -f tube s wi thin the r -f gen =erator housing. If this volt-age is significantly high(8 volts). one of the r =f tubefilaments may be open orthe heater supply multivi-brator is far out of adjust-ment.

-35 -

4-6 SYSTEM ANALYSIS CHECK CHART

The schematic diagram at the end of the manual contains a seriesof test points which are listed below with measurement data takenat each test point. Measurements made at these points providepositive means of isolating a source of trouble to a small circuitarea. When a circuit gives a faulty indication at a tes t point, themeasurement may be analyzed to determine the type of failure,for example, insufficient gain through an amplifier normally in­dicates a weak tube. Distortion may indicate a gassy tube, shortedcoupling capacitor, faulty resistor, etc. A faulty resistor is easilylocated by voltage and/or resistance measurements at the tubesocket terminals and by comparing the readings with those givenin the tube-socket voltage-resistance diagrams at the rear of themanual. A short circuited capacitor is usually located by meas­uring zero or low resistance across the capacitor with an ohm­meter. An open capacitor may be isolated by shunting the sus­peeted component with a new one while noting instrument operationand by looking for an improvement in the usual signs of oscillationor instability. Listed with the check points are paragraph refer­ences for detailed information regarding a particular measure­ment. The indicated test point voltages are made to ground witha 20,000 ohm/volt multimeter. In some measurements a higherimpedance meter or one having greater sensitivity is required andis so noted. In some measurements in the power supply it is moreconvenient to measure voltage from the -165 -volt supply than fromchassis ground and is so indicated. Begin measurements with sig­nal generator set for 0 dbm output level and CW operation, thenshift the controls as instructed in the chart. Follow steps in ordergiven; some steps presume that previous measurements havegiven satisfactory indications. Set the front panel controls asshown below and proceed with the checks in the chart.

Power SwitchMOD. SELECTOR

FREQUENCY RANGEFREQ.

MOD. LEVELAMP. TRIMMEROUTPUT LEVEL

ATTENXTAL CAL GAIN

ONCWD100minimumSet for maximum output.Set for SET LEVEL reading on

OUTPUT VOLTS meter.o dbmmaximum

-36-

Table 4. System Analysis Check Chart

1 Operate as de-scribed in Para.4-6. Set MOD.SELEC TOR to:CW, max. out-putCW, min. out-putPULSE operation

2 Same as Step 1

oex::>o-.D

Step &:TestPoint

3

4

5

6

608DControl Position

Same as Step 1Set for:

CW, max. out­put400'\ MOD. out­putPULSE operation

Same as Step 1

Any posi tion

Set for CW atlow freq. endof:"A" bandliB" band11 Cll band'IDll band11 E" band

NormalIndication

260 vdc,1.4 vac

90 rna dc

95 rna dc

82 rna dc

-165 vdc,5.5 milli­volts ac

+340 vdc,2.7 vac

155 rna dc175 rna dc147 rna dc

+225 vdc5.5 milli­volts ac

7.6 voltsac, squarewave

103 vdc89 vdc87 vdc82 vdc80 vdc

-37-

Pos sible Cause ofAbnormal Indication

Excessive ripple, C42. Lowvoltage, CR6 or excessive cur­rent drawn by following cir­cuits.

See Table 3, Item 2.

Excessive ripple, C40. Lowvoltage, CR4, CR5 or exces­sive current drawn by follow­ing circuits.

See Table 3, Item 3.

See Table 3, Item 4.

When out of oscillation a volt­age of approximately 87 isread on all bands. Check oscil­lator tube and associated com­ponent.

Table 4. System Analysis Check Chart (Contd.)

Step &:TestPoint

7

8

9

10

11

608DControl Position

Set for CW op­eration

Set for CW op­eration. SetOUTPUT LEVELto:minimumSET LEVELmaximum

Set for CW op­eration. SetOUTPUT LEVELto:minimumSET LEVELmaximum

Set for 400'\,Modulation at10 mc and 100mc10% mod.30% mod.50% mod.80% mod.

Set for CW op­eration. SetOUTPUT LEVELto:minimumSET LEVELmaximum

NormalIndication

+110 vdc

Measurevoltageacross R82

o vdc+1. 4 vdc(approx. )+7.0 vdc

+31 vdc+6 vdc(approx. )-7 vdc, -26vdc whendisconnect­ed from r-fgenerator

AC Volts10 mc 100 mc

.48 .31. 3 • 752.2 1.23.7 1.8

Use elec­tronicvoltmeter

+23 vdc- 2 vdc~30 vdc

-38-

Possible Cause ofAbnormal Indication

High voltage indicates a weakV7 or open plate circuit.

With output level set to max.and RANGE selector set be­tween ranges, the d-c voltageshould not exceed -4.5 voltsto ground.

With modulator disconnectedfrom filter FL6, inadequatevoltage range indicates poorV5 or control circuit measuredin Step 11.

Insufficient signal indicateslow amplification farther backin the modulator, see Steps14, 15, and 16.

Rough, insufficient, or exces­sive voltage check R34, R37,R39, and R40.

=II::C1'o00t:lo

. 0C1'

--0ooo00o--0"*I::

.....ro....1-4~

tf.l

o00o--0

Table 4. System Analysis Check Chart (Contd.)

Step &:Test 608D Normal Possible Cause ofPoint Control Position Indication Abnormal Indication

12 Turn off for this 53 ohms 25 ohms indicates shortedmeasurement. C37. infinite indicates open

R58.

13 Set for 400 and 2 vac rms Adjust R 7 to obtain correct

1000"- internal +6.4 vdc voltage, if necessary.

modulation op- change II.eration

14 Set for 400"- Use e1ec- Approximate voltages re-

modulation at tronic volt- quired for modulation of the

10 mc meter r -f output signaL

10% ,017 vac30% .048 vac50% .083 vac "

80% • 141 vac

15 Set for 400"- Use elec- Low output indicates weak

modulation at tronic volt~ VI. Gain should be approx-

10 mc meter imate1y equal for these sig-

10% .068 vac nal levels,

30% . 195 vac50% .32 vac80% .56 vac

16 Set for 400"- Low output indicates weak

modulation at V3. Gain should be approx-

10 mc imately equal for these sig~

10% . 58 vac na1 levels .

30% 1. 66 vac50% 2.8 vac80% 4.8 vac

17 Set for 400"- Low output indicates weak

modulation at CR2 and would be acc ompa-

10 mc nied by low indication on the

10% .014 vac r-f OUTPUT VOLTS meter.

30% . 044 vac See Paragraph 4-14 .

50% ,174 vac80% 1.2 vac

-39-

Table 4. System Analysis Check Chart (Contd.)

Step &Test

Point

18

19

20

21

608DControl Position

Set for CW op­eration. SetOUTPUT VOLTSmeter to read:. 1 volthalf scaleSET LEVELfull scale

Set for 400'\,modulation at10 me10%30%50%80%

Set for CW op­eration at anycheck point

Set for CW op­eration at anycheck point

NormalIndication

.05 vdc

. 16 vdc

.23 vdc

.32 vdc

.39 vac1. 0 vac1. 55 vac2.50 vac

4 vdc

43 vac withJ3 connect­ed to 600ohm load

-40-

Possible Cause ofAbnormal Indication

These voltages vary depend­ing upon the forward resist­ance of CR2 and CR3.

Low voltage indicates weakV18 or V19.

If voltage is below 1 volt andbeat-frequency signals arenot obtainable, check CRI andV9. See Paragraph 4-15.

Low output indicates weakVI0 or Vll.

0'o00

"t1

==II::0'o00t:loo0'

4-7 REPLACEMENT OF ELECTRON TUBES

When replacing tubes in the Model 608D i it is recommended thata check be made on the operation of the instrument before andafter each new tube trial; and if no improvement is noticed~ theoriginal tube should be returned to the socket, Figure 7 locatesall e:' ~ctron tubes in the equipment. Table 5 lists the tubes of thesignal generator with a suggested check and paragraph referenceif adjustments are necessary.

Table 5, Adjustments and ChecksRequired After Tube Replacement

r---------~-------------------------_,.

...0ooocoo...0=ll::

N.0'.-l

.....cd.....1-l11)

U)

TubePosi tion

VI

V2

V3

V4

V5

V6

V7

Check or Paragraph Reference

Check operation with modulation .

Check operation wi th internal modulation.

Check operation wi th internal modulation.

Check operation with internal modulation,

Check range of output level control(should obtain 0 to full-scale deflectionon OUTPUT VOLTS meter).

See paragraph 4-8 .

Check maximum power for CW operation(should obtain full-scale deflection onOUTPUT VOLTS meter),

ocoo...0

V8 See paragra.ph 4-9.

V9 See paragraph 4-10.

VI0 Check loudness of calibrator signal.

Vll Check loudness of calibrator signal,

V12 See paragraph 4 -11,

Vl3 See paragraph 4-1 L

V14 See paragraph 4 -11.

-41-

V20---,5726!6AL5W

VI96AH6

VI66080

V2112AU7

VIS6AH6

Fig. 7. Tube Location Diagratn

0'000t:j

V2 \.11

12AU7 "'-.......0

"'-.\.11\.11

C/)(b

"I-j....I»............-..DN

I»;:lA-

I»0'"0<(b

'=II::0'0(Xl

t:j000'

V36CL6

V56CL6

V6,------J5675 VII

12AT7

V96AU6

V7--6BC4 Vl0

12AT7

VI75687

V15--"'"5651

V14----t­6AU6

VI36080

-42 -

::jj::

Q)

>0

,..0ro'd .

4-8s:=ro

N0"-............ro.....I-iQ)

U)

tntn..........0"-......

..........tn

Qex>0~

Table 5. Adjustments and Checks Required AfterTube Replacement (Contd.)

TubePosition Check or Paragraph Reference

V15 See paragraph 4-1l.

V16 See paragraph 4-1 L

V17 See paragraph 4 -11.

VI8 Check for indication of modulationpercentage.

VI9 Check for indication of modulationpercentage.

V20 Check for indication of modulationpercentage.

V2I Check zero set of PERCENT MODULA-TION meter.

RADIO FREQUENCY OSCILLATOR TUBE REPLACEMENT(Figs. 8, 16)

Replacement of the radio frequency oscillator tube v6 may affectthe calibration of the frequency dial and may change the heatersupply voltage for the oscillator r buffer, and power amplifiertubes. In addition. the plate current of new type 5675 pencil triodetubes may differ widely in a given application. For this reason,the heater voltage must be checked and, if necessary, reset toproper value; plate current must be held to between 18 and 27milliamperes by tube selection. To replace oscillator tube V6 •refer to Figure 8 and proceed as follows:

a. Remove frequency dial and top plate from r -f generatorhousing to gain access to tube compartment. The frequencydial is accurately indexed on its hub by two pins whichassure exact positioning upon replacement of dial on hub.

b. Remove socket from base of v6 by straight pulL

c. Remove cathode clip from tube.

-43-

R F POWER AMPLI FI ER RF OSCILLATOR

Fig. 8. R-F Oscillator and Amplifier Tube ReplacementDiagram

=II::0'o00tJoo0'

PLATE

SPACER

V6

NOTE

___BH RETAINER SCREWS

Y

ALL INDEX LETTERS REFER TO PROCEDURES

IN PARAGRAPHS 4-7 AND 4-8

V------FIBER

1

WRENCH

RETAINER

-44-

-.D00qCO0-.D

*Q)

::-0

.0cd,

'tl~cd

N0'..-cr-4cd....J..l 4-9Q)

U)

U'lU'l

.........0'..-c

.........U'l

qco0-.D

d. Remove the two 6-32 screws holding retainer plate; thenremove plate and fiber spacer.

e. Lift tube gently from hole by straight pull.

f. Replace tube in reverse order of above steps.

g. Using an average ~readings a-c electronic voltm ~ter cali­brated in rms volts. such as the -hp - Model 400A s C orD. measure the voltage on the inside terminal of FLL Ifnecessary, adjust R87 to obtain a reading of 7.1 volts be­tween the inside terminal of FL 1 and ground.

h. With equipment turned offs break green lead to CIS, a feed­thru type capaci tor in the r -f generator tube compartment,and insert a 0-50 ma millimeter,

i. Set the frequency range switch to the E band and turn equip­ment on. Millimeter should read between 18 and 27 maoIf it does not r try another replacement tube.

j. Using the internal beat-frequency calibrator, check thefrequency calibration throughout the range of the signalgenerator, noting points that are significantly off frequency.

k. To correct the frequency calibration at the high frequencyend of all bands simultaneously. adjust trimmer capacitorC18. which is accessible in the tube compartment in r-fgenerator housing, This adjus tment has only minor effectat the low frequency ends of the ranges .

RADIO FREQUENCY AMPLIFIER AND BUFFER TUBEREPLACEMENT (Figs. 8 and 16)

Replacement of the r -f amplifier and buffer tubes can affect theheater voltage applied to r -f tubes in the generator housing andmay also limit the maximum power output available from the sig­nal generator. Both of these possibilities should be checked asdescribed below, To remove r-f amplifier tube V8 and buffer V7,refer to Figure 8 and proceed as follows:

a. Remove frequency dial and top plate from r -f generatorhousing to gain access to tube compartment.

b. For buffer V7 replace tube and proceed with step h.

c, For amplifier V8 remove socket from base of V8 bystraight pull,

-45-

MIXING DIODE CR I

CIlI'llIi....Pol......

=#::

'"o00tJoo

'"

DFREQUENCY METER

FR - 38/U

11111100

~====G) TEST LEAD

(CAPACITIVE COUPLED

TO FREQUENCY COUNTER)

L 7 (ADJUST V9 PLATE)

C61

V9

(SHIELD REMOVED)

CRYSTAL YI

RF GENERATOR ASSEMBLY(REMOVE SIDE PLATE)

MIXER PICKUP LOOP ----..:

AND OUTPUT CONNECTION

Fig. 9. Diagram Showing Adjustment for InternalFreq. Calibrator

o L6 (ADJUST V9 SCREEN)

® C 23 (ADJUST FREQUENCY)

SI GNAL GENERATOR

TS- 510/U

® FILTER FL 7(MEASURE OC VOLTAGE

FROM CALIBRATOR MIXER)

-46-

-1-10

d. Remove cathode clip from tube.

e. Using the special wrench located on instrument chassisconvenient to generator housing. loosen threaded retainerring which holds V8 in housing. Remove retainer ring andneoprene washer.

f. Withdraw old tube and replace with new type 5876 tube.

g. Following replacement of V8. check and. if necessary,adjust the heater voltage as instructed in paragraph 4-8gfor the r -f oscillator tube.

h. Check the power output throughout the full frequency rangeof the signal generator reading the self -contained powerlevel meter wi th the AMP. TRIMMER control set for maxi­mum output. A full-scale reading should be obtainable overthe entire frequency range.

XTAL FREQUENCY OSCILLATOR TUBE OR CRYSTALREPLACEMENT (Fig. 9)

To gain access to the beat frequency oscillator, remove the sidecover to the r-f generator housing. T~le entire crystal oscillatoris constructed on a bracket mounted on the rear wall of the r-famplifier compartment. Mounted on the bracket are three adjust­ments, L6. L7, and C23, L6 and L7 are adjusted for peak outputat the factory, and it is not expected that further adjustment willbe necessary. However. if the frequency of the oscillator isfound to be off by greater than 500 cycles (0.01%). C23 may beadjusted to bring the frequency of the oscillator to 5 megacycles.To check the frequency of the crystal calibrator and ~o Lnake theadjustments described above, refer to Figure 9 :;,nd pl'oceed asfollows:

a. Remove signal generator from its cabinet, connect topower source and allow to warm up for 15 minutes.

b. Remove side plate from the r -f generator housing to gainaccess to the calibrator oscillator.

c. Connect a d-c voltmeter to the outside terminal of filter FL7.

d. Adjust L7 to peak the d-c voltmeter indication. This volt­age should be between 1-1/2 and 4 volts.

e. Adjust L6 (screen adjustment) to dip the d-c voltmeter in­dication. More than one dip is sometimes obtained, anyone of which may be used.

-47-

•

•

ATTENUATOR DRIVE PULLEY(DRIVEN BY SHAFT FROMATTENUATOR DIAL ON FRONT PANEL)

SHAFTLOCKING

NUT

•

ADJUSTABLE LENGTH PULLEYMOUNTING SHAFT

REAR PULLEY

ATTENUATORPROBE DRIVESCREW ANDCABLE MOUNTINGNUTS.

GUIDE SLOT

~OUTPUT SIGNALCABLE TO FRONTPANEL JACK

PISTON TYPEATTENUATORPROBE

ATTENUATORPROBE HOUSING

Fig. 10. R-F Generator Assetnbly Rear View,Showing Output Attenuator Drive Systetn

-48-

=II:0'oex:>t:loo0'

-.0ooQcoo-.0=ll::

Q00o-.0

4-11

f. Recheck setting of L7. Capaci tively couple a lead from V9to any suitable frequency measuring instrument.

g. Adjust C23 to obtain exact 5 mc signal as read on the fre­quency meter. No further adjustment is necessary if therequired frequency and output level are obtained.

REPLACEMENT OF ELECTRON TUBES WITHIN THEREGULATED POWER SUPPLIES

The Jutput voltage from ei ther or both of the regulated power sup­plies may be affected slightly by a change in anyone of the tubeswi thin the supplies. The two power supplies are interdependentin that the setting of the +225 -volt supply depends upon a referencepoint established by the -165-volt supply; therefore, a tube changein the -165-volt supply should be followed by a check of the +225­volt supply. All tubes and components in the power supplies arelocated on the chassis to the rear of the signal generator.

To check the output voltage from the power supplies followingservice or tube replacement, refer to Figure 13 and proceed asfollows:

a. With the MOD. SELECTOR switch set to the 1000 positionand the other controls in any position, turn equipment ono

b. Connect the positive lead of a voltmeter having a sensi -ivityof 5000 ohms per volt or better to ground.

c. Connect the negative lead to the lead connecting both endsof metallic rectifier CR6 on the rear chassis.

d. Voltage should now read -165 volts, If necessarYI adjustR80 to obtain 165 volts. This voltage should then remainstable with line voltage Lhanges between 103.5 and 126,5volts.

e. Reconnect voltmeter with the negative lead to ground andthe posi tive lead to pin 6 of V 13,

f. Voltage reading should be +225 volts. If necessary, adjustR 71 to obtain +225 volts. This voltage mus t remain sub­stantially constant with line voltage changes between 103.5and 126.5 volts.

g. Connect an average -reading a-c vacuum tube voltmeterbetween filter FL 1 (red identification band) and ground.The voltage at this point is the filament voltage for the r-foscillator and r-f power amplifier and is furnished by V17 i

a square -wave multivibrator •

-49-

LOCKING SCREWFOR C37

SIDE

RF OUTPUT CONDUCTOR(SOFT SOLDER J

RF OUTPUT SIGNALPICKUP LOOP

R58 R59(SOFT SOLDER J

'-....._----... ~----")V-IMPEDANCE MATCHING

NETWORK

Fig. 11. R-F Output Attenuator Probe, ShowingPickup Loop and Impedance Matching Network

-50-

0'o00tJ

=II:::0'o00tJoo0'

~

ooQcoo~

::Il:=

Qcoo~

4-12

h. Adjust R87 for 7. 6 volts rms,

ATTENUATOR PROBE REPLACEMENT (Figs. 109 11)

If the electrical components of the output attenuator are damaged,such as described in the "CAUTION" on page lIs repair or re­placement is necessary. This condition may be confirmed bymeasuring either the d-c resistance or the VSWR of the attenuatorat the RF OUTPUT jack. The d-c resistance should be 53 ohmsand the VSWR not greater than 1. 2. If investigation shows anattenuator to be defectives proceed as follows:

CA UTION ~----------,

During removal and replacement of the probes ex­treme care must be exercised. The probe consistsof a cyclindrical metal tube with a series of springcontact fingers around its periphery at one end,which can be accidentally bent or twisted. Also, itwill be noted that one of the fingers is bent towardthe center of the probe slightly, Do not attempt tostraighten it since it has been made this way toassure clearance between the probe and the end ofthe guide slot in the attenuator housing. It is ofgreatest importance to make certain that the probeis not subjected to shock. If the probe is subjectedto shock, the electrical components attached to theend of the probe can be broken or their positionaltered with a consequent change in the electricalcharacteristics of the probe,

a. Turn the attenuator control on the front panel until theprobe reaches the end of its travel to the rear of the at­tenuator housing.

b. Refer to Figure llb. Remove the nut and washer thathold the drive cable in the probe drive screw in the top ofthe attenuator probe. Lift the cable out of the screw slot.

c. Remove probe drive screw from probe body by removinginner nut and unscrewing.

-51-

d. Carefully retnove the probe by sliding it out of the attenua=tor housing.

q00o..0

e.

g.

j.

If the datnage to the attenuator probe is litnited to a burnedout resistor and if a replacetnent resistor is available,the attenuator tnay be repaired by carefully unsoldering theold resistor, using a low tetnperature soldering iron, andreplacing the resistor. Soldering tnust be done quicklyand neatly with low tetnperature solder. Care tnust betaken to duplicate the original worktnanship as closely aspossible by positioning the new part exactly as the old onewas and by applying as little heat in the soldering processas is possible. Capacitor C37 need not be adjus ted unlessit too has been datnaged. This capacitor consists of atnetal pin with a thin plastic coating within a sleeve. Thesleeve is retained by a #4 Allen screw in the side of theprobe body. If the coating on the pin is pierced, the pintnust be replaced. Again it is itnportant to retain the origi­nal positioning. Loosening the set screw shown in Figure11 allows for adjusttnent or replacetnent of the pin andsleeve.

If repair is not possible, the probe and cable tnust be re=placed. It will then be necessary to retnove the RF OUT­PUT jack frotn the front panel and release the cable frotnthe clatnp holding the cable to the top of the side gusset.The entire probe assetnbly tnay then be retnoved frotn theinstrutnent. Replacetnent probes are cotnplete with cableand panel jack and require no adjus ttnent of the itnpedance­tnatching network upon installation.

Insert the new or repaired probe in the attenuator housing.Care tnust be taken in starting the probe into the housingsince the diatneter at the probe contact fingers is slightlygreater than the inner diatneter of the housing. The con=tact fingers should be depressed slightly while startingthe probe into its housing. UNDER NO CIRCUMSTANCESSHOULD THE PROBE BE FORCED.

Replace the split drive screw in the probe, tnaking certainthat the screw slot is parallel to the axis of the housing.

Set the attenuator drive cable in the screw slot and replaceboth washers and nut. Do not tighten the nut. The cabletnust tnove freely through the slot until the probe penetra=tion has been set.

Secure the r -f cable to the clatnp on the side gusset.(Cable routing is shown in Figures 13 and 14.)

-52 -

k. Connect the instrument to a source of 115 -volt a-c power.Turn on the power switch.

1. Unless otherwise specified. the operating controls shouldbe set as follows:

MOD. SELECTORFREQUENCY CONTROL

FREQUENCY RANGEAMP. TRIMMEROUTPUT LEVEL

MOD. LEVELAttenuator

CW20 megacyclesA bandAdjust for max. outputAdjust for SET LEVELCounterclockwiseo dbm

-.0ooQcoo-.0::ll::

Qcoo-.0

m. Connect a power meter. such as the -hp- Model 430B.through a bolometer mount (~hp~ Model 476A or equiva­lent) to the RF OUTPUT jack,

n. Remove r -f generator side plate so that clearance betweenthe attenuator probe and r-f amplifier tank may be observed.

CAUTION ----------j

The following step must be executed as care­fully as possible to insure that the pick-uploop does not make contact with anyone of theamplifier coils. These coils are the poweramplifier tuning coils and are at B+ potential.Contact with the attenuator pick-up loop wouldbe des tructive to the attenuator components.

o. With the attenuator dial set exactly on 0 dbm and the OUT­PUT VOLTS meter set to SET LEVEL. manually advancethe attenuator probe into the housing until the r -f outputsignal is exactly 1 milliwatt (0 dbm) as read on the ex­ternal power meter,

p. Tighten down the nut on the split screw so that the probemay be actuated by its drive system. Carefully check tosee that there is clearance between the various turretcoils and the pick-up loop when the attenuator dial is setto +4 db.

q. Replace r-f generator side plate. Using the power meter.check the output at 0 db (1. 0 milliwatt) at the higher fre­quencies on the B. C. D. and E bands. If necessary. the

-53-

self-co:'1tained output meter calibration can be adjusted bymeans of R62 (see Figure 14). See paragraph 4~15 forcomplete OUTPUT VOLTS meter recalibration instructions.

4-13 REPLACEMENT OF LAMP II

Lamp II acts as a thermal resistance having a high positive tem­perature coefficient and is used to maintain constant output volt­age from the 400 - and 1000 -cycle oscillator. The S6 type lampsused for this purpose ordinarily vary widely from one lamp toanother and produce widely varying output voltage from this oscil­lator. Potentiometer R 7 is provided for adjustment of the oscil­lator output voltage for various S6 lamps.

After the lamp 11 has been replaced~ the oscillator voltage, asmeasured at pin 3 of V2~ should be adjusted to 2 volts rms; if itcannot be adjusted to this value~ another lamp must be tried.

4-14 CALIBRATION OF THE PERCENT MODULATION METER

Recalibration of the PERCENT MODULATION meter may be nec­essary following a repair of the modulation measuring circuits orafter replacement of the meter itself. The method of calibrationoutlined below requires the use of a peak-reading electronic volt­meter capable of measuring a-c voltages to 500 megacycles, suchas the -hp- Model 410B~ and requires a tuned step-up transformerto obtain adequate output voltage from the generator for measure­ment. Basically. this method of modulation measurement con­sists of measuring the peak value of the r -f output signal wi th andwi thout modulation. A doubling of the peak output voltage indi­cated on the multim.eter represents 100% m.odulation of the outputsignal~ while lesser percentages of m.odulation are indicated byproportionally smaller voltage increm.ents.

To measure modulation by the voltmeter m.ethod~ it will be nec­essary to fabricate a tuned circuit sim.ilar to that shown below.Materials at hand may be used as substitutes for those listed.

-54-

=#::C1'o(Xl

t:J-0oC1'

COIL A

COIL B

GJI

...0ooQ00o...0=II::

Q)

>o~'0'Qell

N­.....cd....~Q)

CJ)

Coil form = 3/4 in. dia by approx. 2 in. long.Ceramic. polystyrene or similarmateriaL

Coil A = 5 turns of solid #22 wire spaced 1/8in. between turns.

Coil B-2 turns of solid #22 wire spaced 1/8in. between turns. (Approx. 1/4 in.spacing between coils A and B.)

Tuning capaci tor = 7 to 45 I-ll-lf.

The following procedure for calibrating the PERCENT MODULA­TION meter may be used with either internal or external modu­lation.

a. With the controls set as below. turn the power switch onand allow the instrument to warm up.

Q00o...0

FREQUENCY RANGEMEGACYCLES dial

MOD, SELECTORAMP. TRIMMER

OUTPUT VOLTS meterPERCENT MODULATION

Attenuator

C ban.d75 to 85 mc1000Adjus t for max. outputAdjus t to SET LEVELAdjus~ for 0%o dbm

-55-

to the test apparatus as shown

oo

-hp- Model 410BVHF Vacuum Tube

Voltmeter

oDe)

b. Connect the signal generatorin the diagram below.

-hp- Model 608CVHF Signal Genera tor

c. Set the 410B voltage range switch to the 10-volt a-c range.

d. Adjust the capacitor on the r-f transformer to obtain great­est output as read on the vacuum tube voltmeter.

e. Reading from the 0 to 3 volt scale on the multimeter, ad­just the output attenuator on the 608D for a reading of Ivolt on the multimeter.

NOTE

The actual voltage from the tuned circuitwill be within the 10~volt range; however,the linear portion of the 3-volt scale canbe used as a modulation indicator sincethe I-volt calibration mark now represents0% modulation and the 2 -volt calibrationwill represent 100% modulation, with theintermediate calibrations correspondingto the calibrations on the PERCENT MODU­LATION meter in the signal generator.Accuracy of modulation indication as readfrom the 410B Voltmeter will be within ±5%.

f. Adjust the MOD, LEVEL control for a reading correspond­ing to 1. 8 on the 410B Voltmeter.

"

-56~

g.

h.

i.

Application of high percentages of modulation may resultin a slight rise (1/2 db) in the OUTPUT VOLTS meter in­dication. If necessary, readjust the OUTPUT LEVELcontrol to obtain a reading at SET LEVEL on the OUTPUTVOLTS meter.

Adjust R104 (see Figure 13) to provide a reading of 80% onthe PERCENT MODULATION meter.

Check the meter calibration for other modulation percent­ages, e. g., 1. 1 on the voltmeter corresponds to 10%modulation, 1. 2 to 20%, etc. The setting of R104 may berefined to obtain best overall calibration accuracy of thePERCENT MODULATION meter.

NOTE

-.D •00

ClCO0-.D

*~

> 4-150

~'0.C«I

N0'-.,....,«I....~~

U)

ll'\l!'l

0'-'-..l!'l

Clco0-.D

For this procedure the OUTPUT LEVELcontrol must be set at all times to pro­vide a reading at SET LEVEL on theOUTPUT VOLTS meter.

OUTPUT VOLTS METER CALIBRATION AND R-F POWERMONITOR SERVICE

Recalibration of the OUTPUT VOLTS meter may be necessaryfollowing. replacement of the attenuator probe, components in thepower moni toring circuits, or replacement of the meter itself.If it becomes necessary to replace CR2 or R60 in the power moni­tor assembly, the frequency response of the meter circuit willalso be affected and must be readjusted.

CAUTION

Do not disturb the positioning of the components inthe r~f power monitor assembly (see Figure 15)until instructed to do so in procedure. The posi­tion and lead lengths of resistor R60 and L 17 andthe characteristics of crystal CR2 all affect thefrequency response of the meter circuit, mostlyon the E band and to a lesser degree on the Dband. To restore "flat" frequency response re~

quires care and skill in repositioning.

~57-

The method of calibration outlined below requires the use of a50-ohm bolometer mount and power meter, such as the Hewlett­Packard Model 476A Universal Bolometer Mount and Model 430BPower Meter, to measure the r ~f signal power from the generator.To reset the frequency response of the higher bands, such as fol­lowing replacement of CR2 or R60, the OUTPUT VOLTS metermust first be checked for accuracy as described in steps "a"through "i" below, then adjusted as described in step "j". Pro~

ceed as follows:

a, Connect the 608D to a source of 115~vo1t a-c power. Turnon the power switch and allow to warm up with the operat­ing controls in the following posi tions:

MOD. SELECTORFREQUENCY CONTROL

FREQUENCY RANGEAMP. TRIMMEROUTPUT LEVEL

MOD. LEVELAttenuator

CW75 to 80 megacyclesC bandAdjus t for max. outputAdjust for SET LEVELExtreme counterclockwiseo dbm

b. Connect the power meter and bolometer mount to the RFOUTPUT jack on the signal generator.

c. With the attenuator set for exactly 0 dbm, adjust the OUT­PUT LEVEL control to obtain exactly 0 dbm on the ex­ternal power meter.

d. If necessary, adjust R62 to obtain an exact reading at SETLEVEL on the self~containedOUTPUT VOLTS meter.

e. Using the external power meter, check the 0 and +7 dbcalibration points of the OUTPUT VOLTS meter (points-4 and +3 decibels from the 0 dbm level).

f. Adjust the OUTPUT LEVEL control to obtain -4 dbm asread on the external power meter. If necessary, adjustR62 to obtain a reading of 0 db on the s elf -contained OUT­PUT VOLTS meter.

g. Set OUTPUT LEVEL control for +3 dbm as read on theexternal power meter. If necessary, adjust R61 to obtaina reading of +7 db on the self-contained OUTPUT VOLTSmeter.

h. Because the two adjustments R61 and R62 are interactive,steps "f" and "g" must be repeated to obtain best overallaccuracy of calibration.

-58-

=II::0'o00t)oo

-0'

..0ooQ00o..0=II:::

Q00o

'"

i. Recheck accuracy of calibration at SET LEV 1!::L (+4 dbm)and, if neces sary, adjus t R62 to obtain an e~~aet readingat this point.

j. Recheck calibration at SET LEVEL at frequencies of 100,250, and 400 megacycles. If the calibration is high or lowat the higher frequencies, the OUTPUT VOLTS meterreading may be corrected by adjusting the inductance ofL 17. Shortening the coil (increasing the inductance) willdecrease the meter reading as shown in the diagram below.Lengthening the coil (decreasing the inductance) will in=crease the meter reading.

CAUTION

Great care should be taken to changeonly the length of the coil and not toshift the posi tions of any other com­ponents in the power monitor assembly.

If the frequency response is satisfactory at all frequencies up toapproximately 300 mc but tends to rise or fall at the higher fre­quencies, the pigtail connection of resistor R60 which connects tocoil L 17 may be adjusted very slightly to raise or lower the meterreading at the higher frequencies only. Again, great care mustbe used to adjust the positioning of only one component at a timeand to follow each adjustment with a power measurement to seethe exact effect of the adjustment. In general, increasing thecapaci.ty between this pigtail and ground may be expected to de­crease the meter reading at only the higher frequencies.

The graph on the next page shows the increase or decrease in thereading of the OUTPUT VOLTS meter that is obtained at differentfrequencies when making each one of the three possible adjust­ments. Only minor adjustments should be made (very small changein physical position), using the graph for a guide as to the approxi­mate results that may be expected.

-59-

(!)

z0<tlJ.J SETa:: LEVEL

a::lJ.Jf-lJ.J~

(f)

~0>f-:::>a..f-:::>0

10 100 200

MEGACYCLES

-60-

300 400

0'o00t1

"II::0'o00tloo0'

4-16 REPAIRING THE CALIBRATOR OSCILLATOR

To replace any of the components in the frequency calibratoroscillator circuit, other than the tube and crystals, the oscil­lator chassis must be removed from the r-f generator assemblyas follows:

a. With signal generator out of its cabinet, remove theside plate from the r -f generator housing.

b. Unsolder the shielded heater power (black) lead fromthe feed-thru capacitor in the top of the compartment.

c.

d.-!)

0 e.0Qco0-!)

::II::

~

:>0

..a ,ro'0

s::ro

N •0'...-4

......ro.....101Cl.l

(f.)

l!)l!)

..........0'................l!)

Q000-!)

Unsolder the shielded plate (white) lead from the tiepoint in the top of the compartment.

Unsolder the output lead from filter FL7.

Remove the two 6-32 machine screws attaching theoscillator chassis to the generator housing. The oscil­lator chas sis is now free to be removed.

-61-

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orm

al.

)b

ein

gg

reate

rth

an

the

ind

icate

dC

heck

mo

du

lati

on

of

r-f

carr

ier

by

vie

win

gam

ou

nt.

on

osc

illo

sco

pe.

7.D

isto

rtio

no

fth

em

od

u-

Weak

r-f

po

wer

am

pli

fier

V8

.C

heck

dis

tort

ion

of

the

mo

du

lati

ng

sin

ela

tio

nen

velo

pe,

par-

Weak

r-f

oscil

lato

rV

6.

wav

efr

om

mo

du

lato

rV

5.

ticu

larl

yat

hig

hm

od

u-

Dis

tort

ed

mo

du

lati

ng

wav

eC

heck

by

rep

lacem

en

to

fV

8.

lati

on

lev

els

.fr

om

oscil

lato

rV

2o

ram

pli

fier

Ch

eck

r-f

dri

ve

top

ow

er

aU

lpli

fier,

V3

.sh

ou

ldb

e4

to11

vo

lts.

8.

Inte

rnal

mo

du

lati

on

Lo

ose

3-w

att

laU

lp11

inm

od

u-

Tig

hte

nla

mp

inso

ck

et.

no

tp

oss

ible

.la

tio

no

scil

lato

rV

2.

9.R

Fo

utp

ut

sig

nal

do

es

Weak

cath

od

efo

llo

wer

V4

inR

ep

lace

V4

.n

ot

go

tozero

wh

en

mo

du

lato

r.g

en

era

tor

issw

itch

ed

toP

UL

SE

op

era

tio

nan

dn

op

uls

es

are

ap

pli

ed

.

POWER SUPPLY(REAR CHASSIS)

R82 (RF FIL. ADJBEHIND GUSSET)

RF GENERATOR ASSeMBLY(TUBE COMPARTMENT)

Fig. 12. Model 608D Signal Generator Right Side View,Cabinet Rem.oved

0'o00tl

"#:0'o00tjoo0'

RF GENERATORASSEMBLY

(TUNING COMPARTMENTSBEHIND THIS SIDE PLATE)

FLIFL3FL6 FL4 FL2 FL5

ATTENUATORCABLE

• •

-64-

MODULATION METER AMPLIFIER POWER SUPPLY

_------..A....------ _------""'--------_r ~

R104(M2 METER CALIS. ADJ,)

R89 R77 R68

C54

C39 C55 C52A

-.0ooQCOo-.0=II::

XV18 XVI9 XV20

C40

~----R71(-160V ADJ.)~1-;..:.-----R80(t225V ADJ.)

...........:...-XVI4~.,:--XVt~

---C45

---C46ATTEN, PROBE a CABLE

1........_---- ,,- )v

POWER SU PPLY

Qcoo-.0

CR4 CR5 eRG T2

HEATER SUPPLY MULTIVIBRATOR

Fig. 13. Model 608D Signal Generator Rear View,Cabinet Removed

-65-

0'o00tl

enro

"Ii....III.....FILAMENTS

Tf

PRIMARY

\......----v,,------)

ATTEN.DRIVEPULLEY

HIGH VOLTAGESECONDARY

C36 VIO

T3 VII

CRYSTAL CALIBRATORAMPLIFIER

MODULATOR SECTIONA

( 'IC7 R39

Cl C8 Cl1 CI2

VI V3 V4 V5

j 1

V2 I'

R7 C5(OSCAMPLITUDE)

MODULATIONOSCILLATOR

51MOD.SELECTOR

""..... v,-------l ""'----...vJ""---)

Fig. 14. Model 608D Signal Generator Left Side View,Cabinet Removed

"*l:0'o00t1oo0'

-66-

RF AMP COMPARTMENT,

AMPLIFIER va

TUNINGCAPACITOR

C 17B

RF OSC COMPARTMENT,

OSCILLATOR V6

TUNINGCAPACITOR

CI7A

R57 R45 R44

-.0ooQCOo-.0

*

......ell.....H\1)

U)

QCOo-.0

RF TUBE

OUTPUT ATTENUATOR

RF POWER MONITOR--7:2--r--;ASSEMBLY

MIXER OIODE CRI---~:;"

C6t (STANDOFF INS)--~7"""·

5 MC OSCILLATOR V9

-AMPLIFIER COIL TURRET

CALIBRATOR COUPLING LOOP

CRYSTALYI

HETERODYNECALIBRATOR

Fig. 15. R-F Generator Assembly, Side Plate Removedto Show Tuning Compartments

-67-

+225 V DC TO OSC.a AMPL.

CATHODE CLIP

_HEATER POWER

"--_--OUTPUT FROM RFPOWER MONITOR

-----AMPL. HEATER FILTERFL9

_~---AMP. TRIMMER C32

____----TUBE RETAINER RING(C 26)

.~-;-----HETERODYNE SIGNALFROM CALI BRATOR

OSC. TRIMMERCIS

• ,,_.-;.-----6.3 VAC FOROSCILLATOR V9

•

V6TUBE SOCKET

TUBE SOCKETva

OUTPUT ATTENUATOR-----_--!._HOUSING

MODULATION TO ~-------'=--~=---­

RF AMPL.

RF AMPLI FIER --------.,;O--.:::~VS

TUBE RETAINER

RF BUFFER----- _V7

RF OSCILLATOR -----iii~.J!rr:.:--;J~~V6

DIAL INDEXING PINS--t--"__-~L-_.

FREQUENCY DIAL HUB(DIAL REMOVED)

Fig. 16. Tube Compartment of R-F Generator Assembly,Frequency Dial and Cover Plate Removed

=II:a­o00t:looa-

-68-

60

8D

5/1

9/5

5S

eri

al

19

2an

dab

ov

e#

60

8D

00

6

MO

DU

LA

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NIN

DIC

AT

OR

---------------, I I

fOI I

PE

RC

EN

TM

OD

J

~ "--"

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UT

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TER

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RV

IS,

VI9

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-------~--------~

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RV

7

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RF

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OR

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TO

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V9

I'I

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f-----, I I I I I I I I I I

CATH

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OWER

V4

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UTLE

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/./

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TION

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RI

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ZV

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ION

OSCI

LLA

TOR

V2

MO

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Rr--------------

I'

I

I I I Ir----

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T.

MO

D·I

I

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TION

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ILI

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ER

Fig

.1

7.

Sig

nal

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cin

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lock

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gra

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0­Cext:;

CIl('1)I-t.....~

EGULATEO'EO 8Y R80

EGULATEOED BY R71

1000 CPSWAVEo BY R87

+ +

RECTIFIER +360V DC VOLTAGE REGULATOR +225VOC RINPUT OUTPUT ADJUSTCR4 - CRS V12. V13, V16B

...±. +

HEATER SUPPLY 7.6V RMS OF

MULTIVI BRATORSQUARE

OUTPUT AOJUSTE- V17 -

+ +

RECTIFIER +260V DC VOLTAGE REGULATOR -/65V DC RINPUT OUTPUT ADJUST.

CR 6 V14. VI6A-

REFERENCE TUBEVIS

Fig. 17a. Block Diagram of Power Supply

::It::0'o00t)oo0'

-70-

NOTES PERTAINING TO ALL

TUBE SOCKET VOLTAGE-RESISTANCE DIAGRAMS

1. CONDITIONS OF MEASUREMENT

Unless otherwise noted, measurements madewith respect to chassis ground using volt­meter having 20, OOO-ohm-per-volt sensitivityand with front panel controls at the followingsettings:

FREQUENCY 100 MCMODo SELECTOR ~~ lOOO'\,MOD. LEVEL ..,-- 30%OUTPUT LEVEL -- Set Level

R 71 and R80 in the power supply sectionwere set to provide the normal supply volt­ages of +225v and ~165v, respectively,

2. 20, OOO-ohm-~ er-volt meter cannot beused for this measurement since itwill load the circuit and provide anerroneous reading. A vacuum-tubevoltmeter should be used here,

......cd....!-i(\)

U)

o00o-.D

3, Reading taken at minimum and maxi­mum setting of OUTPUT LEVEL controL

-71-

XV

I6

S0

7X

V3

6C

l6X

V4

6C

l6X

V5

6C

l6N

.C.

0.0

.

OV

0.0

.

22

5V

90

0.0

.

lOO

K

AS

PIN

1

6.3

VA

C

10

0K

22

5V

-32

VTO

+2

4V

(SE

EN

OTE

S2

a3

)6

40

K'

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TO

+3

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(SE

EN

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3)

90

0.0

.

N.C

.

0.0

.

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OV

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22

V

22

5V

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VA

C

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II I

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.

lOO

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C

I L-, I I I

-----------, I I

N.C

.

49

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15

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K

30

K

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0.0

.

NC.

4.0

V

1.2

5M

1.7

5V

13

5V

I 1 1 1_

63

VA

C0

.0.

4.0

V

1M

30

K

4S

0K

22

5V

OV

1M

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12

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OV

12

5V

60

V2

20

K

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ov

60

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0.0

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lOO

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0.0.

OV

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0.0

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OV

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OV

(SE

E

RIG

HT

SID

E

III

I

11

0[(0

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------

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ov

ov

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SV

0.0

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AC

(SE

EN

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AC

---o.n

:1.

1M

0.0

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6.3

VA

C0

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SO

K

OV

29

V

30

K

r--------

I I I I I I I6

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1/1

40

.0.

I6

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AC

0.0

.

6.3

VA

C

OV

OV

lOO

K

50

0.0

.

1.1

5M

16

5V

O.n.

1.1

V

I -.J

N I

XV

25

81

4/1

2AU

7X

VIO

58

14

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AU

7X

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58

14

/12

AU

7

Fig

.1

8.

Tu

be

So

ck

et

Vo

ltag

ean

dR

esis

tan

ce

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gra

tn,

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ht

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hassis

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oa

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60

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5/1

9/5

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eria

l1

92

an

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08

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06

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OV

2M

30

V

16

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on

6.3

VA

C

0.11

2M on

lOO

K

15

0K

16

0V

39

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22

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6.3

VA

C

XV

13

60

BO

OV

on

2M

0.0

.

150

K3

90

V

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16

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20

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I.IS

M

16

5V

0.11

22

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<

XV

21

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I4/1

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6.3

VA

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=6

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AC

6.3

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C=

=2

2S

V6

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AC

lOO

K=

B4

V2

2S

V1

0M

6.3

VA

C

=lO

OK

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B4

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ISK

11M

6.3

VA

C

XV

20

57

26

XV

16

60

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+9

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on

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1.2

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120

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)

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.

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.

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.

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.

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--..

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--------------------------

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I,r-

----

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=\

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...:0

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i--r

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----

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Fig

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be

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et

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lta

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an

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esi

sta

nce

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gra

m,

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Gen

era

tor

Assem

bly

SECTION V

TABLE OF REPLACEABLE PARTS

NOTE

Any changes in the Table of Replaceable Parts will belisted on a Production Change sheet at the front of thismanual.

When ordering parts from the factory always includethe following information:

Instrument model numberSerial number-hp- stock number of partDescription of part

TABLE OF REPLACEABLE PARTS

\"'ircuitRef.

C 18, 32,59

C23

C37

Description

Capacitor: variable, glass dielectric.3 to 3 ~~f

Capacitor: variable, glass dielectric1 to 12 ~~f

Consists of insulated metal pin andbras s sleeve

CAPACITOR: fixed, mica dielectric,±100/0, 500 vdcw (unless otherwisenoted)

-hp­Stock No.

13 -3

13 -21

608A -34Q608A-34P

Mfr. * & Mfr s .Designation

Corning Glass Wk~#680015

Corning Glass Wks.#683040

HPHP

e2, 3 5600, 300 vdcw

C4 470, ±50/0

C6, 50, 53 1800

C 10 39 0 s ±50/0

C 13 100

C 16 100, button type

C25 50, (2 required)

C29 56

C33 65

CAPACITOR: fixed, ceramic dielectric,±50/0, 500 vdcw, value' in I-lJ.lf(unless otherwise noted)

C9 r 34, 35, 10,00041,43,44,49,51,57,66

C14, IS, 1,000, ±200/0. feed-thru type28, 31

C19 5,000

C20,21 47

15-42

15-90

14-47

14-43

14-100

15-53

512 -112

15-48

608D-82

15-43

15-68

15-47

15-34

A, Type 1464X

Z, KR 1347

V, Type OXM

V, Type OXM

V, Type OXM

Z , Type M -1 00

HP

Z, Type M-I00

HP

A, Type BPD. 01

L, Style 327

A, Type BPD. 005

A, SI47 I-lJ.lf ±50/0NPO

*See "List of Manufacturers Code Letters For Replaceable Parts Table."

-79-

TABLE OF REPLACEABLE PARTS

CircuitRef.

C22

C24

C26, 65

Description

10, ±O. 5 ~~f

2.2, ±100/0

2,000, ±200/0, disc type

-hp­Stock No.

15-30

15-52

15-80

Mfr. * & Mfrs.Designation

A, CI-l

DD, #GA-4

A, BPD.002

C30

C38, 64

C60

C61

0.47

550, ±100/0

5, ±0.5 Wf

5 (approx.) standoff insulator

CAPACITOR: fixed, paper dielectric,±100/0, 400 vdcw, value in ~f

(unless otherwise noted)

15-74 DD

15-37 Z, Type M-I00

15-29 A, CI-l

34-9 HP(2 reqd.)

C1, 8,11, O. 1, ±200/012,27,36,39,56,58

C5 0.22

16-35

16-48

CC, 68P 10404

CC, 67P22494

C47,48

C68

0 0 01, 600 vdcw

Special trimmer, fine freq. adj.

CAPACITOR: fixed, electrolytic,450 vdcw, value in ~f

16-11 CC, 73P 10306

608D-59H HP

C7AB, 10, dual sectionC52AB,C55,46AB

C40, 42 80

C45 45

18-32

18-34

18-33

J, CE42F100R

J, CE41F800R

J, CE41F450R

CR1/7 Rectifier, crystal 212-GllA HP

CR2/3 Rectifier, crystal 212-1N82 HP

CR4/5 Rectifier, metallic 212-104 Int'l. Rec t.B13D1NTBGX

*See "List of Manufacturers Code Letters For Replaceable Parts Table."-80-

TABLE OF REPLACEABLE PARTS

CircuitRef.

CR6

Description

Rectifier, metallic

-hp­Stock No.

212-103

Mfr. * & Mfrs.Designation

Int'!. Rect.A9BINTBGX

Fl Fuse, 3.2 amp 211-45 T, 31303.2

F3 Fuse, .25 amp 211-6 T, 312.250

FLI/4/7 Filter, Radio Frequency: red 608A-27A HP

FL2/3/5 Filter, Radio Frequency: green 608A-27D HP

FL6 Filter, Radio Frequency: blue 608D-27C HP

FL8 Filter, Radio Frequency: white 608D-27B HP

FL9 Filter, R. F. Choke 608D-60D HP

II

13, 14

Lamp, Incandescent: 3 watt

Lamp, dial illuminating; lamp, pilot

211-4

211-47

o

o

Jl/2 Connector, BNC female 125-UG- HP290/U

J3 Connector, Receptacle: phone jack 124-11 KK, SF-JAX-21

J4 Panel Jack, body G-76A HP

J4D Bushing G-76A-l HP

J4A Bead "A" (large) G-76A-2 HP

J4B Bead "B" ( small) G-76A-3 HP

J4C Spacer G-76A-4 HP

J4E Contact, female 125-49 HP

J5 Connector, Receptacle: motor base 125-25 0, #2711socket

*See "List of Manufacturers Code Letters For Replaceable Parts Table."-81-

TABLE OF REPLACEABLE PARTS

Circuit -hp- Mfr. * &1 Mf r s .Ref. Description Stock No. Designation

L6/7 Coil, Variable: 10-20 ~h 48-22 MM, #32

L8 Choke, R.F. : 4. 5 ~h 608D-60C HP

L9 Choke p R. F.: 4. 5 ~h 608D-60J HP

L10/11 Choke p R.F. : 4. 5 ~h 608D-60K HP

M1

M2

04/5/6

Meter, Microammeter: 50 microamp

Meter, Milliammeter: 1 milliamp

Knob, round p w / skirt

112 -62

112 -56

37-11

Weston #301

Weston #301

Kurz=Kasch Inc. ,S-380-64-DD-L­522

03

07/8

010

012

013

014

015

016

017

Knob, round p (fine freq. adjust)

Knob, round, 3/4 in. dia.

Knob, bar

Knob p round, w/skirt, counterbored

Knob, attenuator, with dial

Knob. frequency vernier dial

Handle, frequency vernier

Dial, frequency vernier

Window p attenuator dial

Knob p fine frequency adjust

RESISTOR: fixed, composition,1/5 watt, ±10% tolerance

608D-74B HP

608D-74A HP

37=19 Dimeo-Gray Co.46A42256

212A-74A HP

608D-40A HP

612A-74 HP

G-74A HP

608D-40B HP

G-99C HP

608D-74B HP

R60, 109

R108

100 ohms

27 ohms

21-100

21-27

F p Type 997CX

F, Type 997CX

*See "List of Manufacturers Code Letters For Replaceable Parts Table."-82-

•

TABLE OF REPLACEABLE PARTS

Circuit -hp- Mfr. * & Mfrs.Ref. Description Stock No. Designation

Rl10 47 ohms 21-47 F, Type 997CX

RIll 150 ohms 21~150 F, Type 997CX

RESISTOR: fixed, composition,1/2 watt, ±10% tolerance,(value in ohms unless otherwisenoted)

R16-, 24, 26 56 23-56 B, EB 560132,39,89,95

R41 180 23-180 B, EB 1811

R46. 12 23-12 B, EB 1201

R48 270K 23-270K B, EB 2741

R49 470 23~470 B, EB 4711

R51 lOOK 23-100K B, EB 1041

R8 , 94 470K 23~470K B, EB 4141

R1l4 1000 23-1000 B, EB 1021

R1l7 100 23-100 B, EB IOU

RESISTOR: fixed, composi tion, 1 watt,±10% tolerance(value in ohms unless otherwise noted)

RI, 115 56K 24-56K B, GB 5631

R9, 66,70 150K 24-150K B, GB 1541

~ ~

RIO, 119 1500 24-10 5K B, GB 1521

RIl, 22,53 1M 24-1M B, GB 105169,76,78,101

R12 lOOK 24-100K B, GB 1041

R8, 13, 6B, 1000 24~1000 B, GB 102177, U8

*See "List of Manufacturers Code Letters For Replaceable Parts Table. II

-83-

TABLE OF REPLACEABLE PARTS

Circuit -hp- Mfr. * & Mfrs.

Ref. Description Stock No. Designation

RI5,23, 470K 24-470K B, GB 474130,38

R19,50 10K 24-10K B, GB 1031

R25,82 330 24-330 B, GB 3311

R29 39K 24-39K B, GB 3931

R31 560K 24-560K B, GB 5641

R34,52, 120K 24-120K B, GB 124154

R36 180 24-180 B, GB 1811

R40 180K 24-180K B, GB 1841

R57 470 24-470 B, GB 4711

R65 12K 24-12K B, GB 1231

R67 1. 8M 24~ 1. 8M B, GB 1851

R72,79, 220K 24-220K B, GB 224181

R73 27K 24-27K B, GB 2731

R 75,83, 33K 24-33K B, GB 333186

R84.85 68K 24~68K B, GB 6831

R90,91 82 24-82 B, GB 8201

R93, 98 82K 24-82K B, GB 8231

R96 150 24-150 B, GB 1511

R99 1800 24-1800 B, GB 1821

RI00 10M 24-10M B, GB 1061

RI05 220 24-220 B, GB 2211

*See "List of Manufacturers Code Letters For Replaceable Parts Table. "-84-

TABLE OF REPLACEABLE PARTS

Circuit -hp- Mfr. * & Mfrs.Ref. Description Stock No. Designation

RESISTOR: fixed, composition,2 watt, ±10%

R14,44 12K 25-12K B, HB 1231

R17,18 8 0 2K 25-8.2K B, HB 8221

R20 2.2K 25-2.2K B, HB 2221

R21 18K 25-18K B, HB 1831

R28,92, 22K 25-22K B, HB 223197,102,107

R42 470 25-470 B, HB 4711

R55 27K 25-27K B, HB 2731

R74 68K 25-68K B, HB 6831

RESISTOR: fixed, wirewound,±10%, 10 watt(unless otherwise noted)

R27 5K, ±1%, 5 watt 26-45 Dale Prod•• Inc.#RS-5

R33 15K 26-25 S, Type 1-3/4E

R43 5000 26-8 S, Type 1-3/4E

R45 3000 26-3 S, Type 1-3/4E

R47 6300 26-61 S, Type 1-3/4E

Rl16 7500 26-9 S, Type 1-3/4E

R121 1/2, ±2Q'%, 5 watt 26-76 S

R35 7500, ±5%, 20 watt 27-24 S

*See "List of Manufacturers Code Letters For Replaceable Parts Table."- 85-

TABLE OF REPLACEABLE PARTS

CircuitRef. Description

RESISTOR: variable, cOtnposition ±10%

-hp­Stock No.

Mfr. * & Mfrs.Designation

R2 20K, 2.25 watt, R. H. log taper 210-70 HP

R7, 61 2000, ±20% 210-14 HP

R37A,B 2K-50K dual 210-71 HP

R56 1M, ±20%, R. H. log taper 210-66 HP

R62 25K, ±20%, 1 watt 210-11 G, BA1-010-1990

R 71, 80 50K 210-36 HP

R87 1500, linear taper 210-33 HP

R104, 106 10K, linear taper 210-35 HP

Sl

S3

T1

T2

T3

Switch, Rotary: 5 position

Swi tch, Toggle

Transfortne'r, Power

Transfortner. Audio: filatnent type

Transfortner. Audio: phone

310-138

310-21

910-110

912 -45

912-40

Oak Mfg. Co.61354HC

HP

HP

HP

HP

VI Tube: 6BQ7 212 -6BQ7 ZZV2/21 Tube: 12AU7 212-12AU7 ZZV3/4/5 Tube: 6CL6 212 -6CL6 zzV6 Tube: 5675 212-5675 ZZV7 Tube: 6BC4 212-6BC4 ZZV8 Tube: 5876 212-5876 ZZV9/12/14 Tube: 6AU6 212-6AU6 ZZV10/11 Tube: 12AT7 212-12AT7 zzV13/16 Tube: 6080 212-6080 ZZV15 Tube: 5651 212-5651 ZZV17 Tube: 5687 212-5687 ZZV18/19 Tube: 6AH6 212-6AH6 ZZV20 Tube: 6AL5 212-6AL5 ZZ

*See "List of Manufacturers Code Letters For Replaceable Parts Table. "-86-

TABLE OF REPLACEABLE PARTS

CircuitRef. Description

WI Power Cord

XF 1 Fuseholder

XII Lampholder, candelabra base

X13 Lampholder, dial illuminating

XIIA Lamp, locking spring

XI4 Pilot light holder

XVI. 2, 3, Tube socket, 9 pin noval4,5,7,10,11,17,21

XV9,12, Tube socket, 7 pin miniature14,15,18,19,20

XV13,16 Tube socket, octal

-hp­Stock No.

812-68

140-16

145 -15

145 -13

146-15

145 -2

120-10

120-11

120-7

Mfr. * & Mfrs.Designation

HP

T, 342003

Leecraft Mfg. Co.#659. 1

#708-1

HP

II, B10B-121

Elko. 377PH

E1ko. 316PH

E1ko. 335BC

XV6/8 Tube socket, pencil triode filament 120 -12contact assembly, oscillator cathode

H, 54A16325

25

Spacer, Osc. Grid~ ".

Spring, detent

Roller. detent

Turret Assembly, Amplifier

Turret Blank, Amplifier

Turret Blank, Oscillator

Turret Assembly, Oscillator

Attenuator Probe Assembly

Attenuator Drive Cable, 36" long

Frequency Dial Window

Bezel, frequency window

608D-59A HP4

608D-59C HP

608D-59D HP

608D-60A HP

608D-83A HP

608D-83B HP

608D-60B HP

608D-34 HP

816-3-608- HPD

608D-83C HP

608D-83E HP

Clamp. tube, for V13/16 140-46 HP

*See "List of Manufacturers Code Letters For Replaceable Parts Table."-87-

TABLE OF REPLACEABLE PARTS

CircuitRef. Description

Clamp, tube, spring (short)

Clamp, tube, spring (Med.)

Contact Assy. for oscillatorpickup coil

Contact, Osc. grid

Contact, Amp. cathode

Insulator Card, attenuator

Insulator, ceramic shoulder bushing

Insulator, standoff, ceramic:

Insulator, standoff, ceramic1/2" long x 1/2" diaD

Spacer, ceramic5/8" long, 1-1/2" diaD

Wrench, spanner

-hp- Mfr .• & Mfrs.Stock No. Designation

\

140-12 HP

140 -13 HP

608A-IOOK HP

608A-IOOV HP

608A-IOOW HP

608A-34C HP

34-9 Gen. ·CeramicsCorp. # 1493 -00

34-34 Gen. CeramicsCorp. # 1023 -04-

3/4"

34-11 G

34-10 HP

612A-38A HP

XYI

Yl

Socket, Crys tal

Crystal, 5 megacycle

120-37

41-34

H, #54A-17358

Knight

*See "Lut of Manufacturers Code Letters For Replaceable Parts Table."-88-

.,

LIST OF MANUFACTURERS CODE LETTERSFOR REPLACEABLE PARTS TABLE

("I")

I.!)I­I

N-

Code Letter

ABCDEFGHHPIJKLMNoPRSTVXZAACCDDEEFFHHIIKKLLMMZZ

90BY013

Manufacturer

Aerovox Corp.Allen-Bradley Co.AlTIperite Co.Arrow, Hart and HegelTIanBusslTIan l\1anufacturing Co.CarborundulTI Co.CentralabCinch Manufacturing Co.Hewlett-PackardClarostat Manufacturing Co.Cornell Dubilier Electric Co.Hi-Q Division of Aerovox Corp.Erie Resistor Corp.Federal Telephone and Radio Corp.General Electric Co.General Electric Supply Corp.Girard-HopkinsInternational Resistance Co.LectrohlTI, Inc.Littelfuse, Inc.MicalTIold Radio Corp.p. R. Mallory Co., Inc.SangalTIo Electric Co.Sarkes TarzianSprague Electric Co.Stackpole Carbon Co.Sylvania Electric Products, Inc.Western Electric Co.AlTIphenolDial Light Co. of AlTIericaSwitchcraft, Inc.GrelTIar Mfg. Co.Carad Corp.Any tube having RETMA standard characteristics

CLAIM FOR DAMAGE IN SHIPMENT

The instrument should be tested as soon as it is received. If it failsto operate properly, or is damaged in any way, a claim should be filed with thecarrier. A full report of the damage should be obtained by the claim agent,and this report should be forwarded to us. We will then advise you of the dis­position to be made of the equipment and arrange for repair or replacement.Include model number, type number and serial numher when referring to thisinstrument for any reason.

WARRANTYHewlett-Packard Company warrants each instrument manu­

factured by them to be free from defects in material and workman­ship. Our liability under this warranty is limited to servicing oradjusting any instrument returned to the factory for that purposeand to replace any defective parts thereof (except tubes, fuses andbatteries). This warranty is effective for one year after deliveryto the original purchaser when the instrument is returned, trans­portation charges prepaid by the original purchaser, and which up­on our examination is disclosed to our satisfaction to be defective.If the fault has been caused by misuse or abnormal conditions ofoperation, repairs will be billed at cost. In this case, an estimatewill be submitted before the work is started.

If any fault develops, the following steps should be ·taken:

1. Notify us, giving full details of the difficulty, and includethe model number, type number and serial number. On receipt ofthis information, we will give you service instruction or shippingdata.

2. On receipt of shipping instruction, forward the instru­ment prepaid, and repairs will be made at the factory. If request­ed, an estimate of the charges will be made before the work beginsprovided the instrument is not covered by the warranty.

SHIPPINGAll shipments of Hewlett - Packard instruments should be

made via Railway Express. The instruments should be packed in awooden box and surrounded by two to three inches of excelsior orsimilar shock-absorbing material.

DO NOT HEStTATE TO CALL ON US

90BY013

HEWLETT-PACKARD COMPANY

l:abora/~ryJnstrumrnt(J;jr JpmfandAccuracy395 PAGE MILL ROAD '!!.fJ PALO ALTO,CALIFORNIA

(.{- - - - MODULATION OSCILLATOR - - - - - -""'\

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R96150

VOLTAGE AMPL.

V196AH6

R88470K

+225VDC (REGULATED)

VOLTAGE AMPL.

VIS6AH6

R8956

{- - - ~ - - - - - - MODULATIO~

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F3

IFUSEI

IDC 0.25AMPI

RI78.2K

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V 16B~6080

SERIESREGULATOR

V16A46080

C46A10

C4545

+

+

13

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R71 R7050K 150K

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VI55651

4

R28C5 RI4 22K.22 12K SID R22

+ C7A 1M R31

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4. POLARITY OF CRYSTAL DIODES

3. POWER TRANSFORMER PRIMARY SHOWNOPERATION. TO CONNECT FOR 230 VOA4 FROM AI AND A5 FROM A2, THENTOGETHER.

NOTES:I. RESISTANCE VALUES IN OHMS. CAPACITY'

AND INDUCTANCES IN MICROHENRIES UNI

K' 1000 ---::--. GROUND

2. WAFER SWITCHES VIEWED FROM SHAFT ISHAFT END. "B" CIRCUIT SECOND FROMIN MAX. CW (EXT. MOD.) POSITION.

+225 V DC (REGULATED)

----------UPPER (TUBE) COMPARTMENT

~RB5>6BK

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OUTPUT LEVELCONTROL

V56CL6

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R99< IBOO

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NOTES:I. RESISTANCE VALUES IN OHMS, CAPACITY VALUES IN MICROFARADS

AND INDUCTANCES IN MICROHENRIES UNLESS OTHERWISE SPECIFIED.

K = 1000 ~ = GROUND

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t-... ~/.lF ~ I 550I:l~F L8 I 'C~ I

- C60 ~_---<"""--_'\}----'-_-~""I_. 4.51 lOOK" I-- ,......, J- , "11 RIIO I 1\ I C I~ I CI6 47 I I

I 100/.l/.lF 3:J5~/.lF ~ == < RII7 L f- J

C25 I (i) I RA~GE L4 ~ ~~g < 100

~~~ 'I > ~'-----+-----"Il\' I 7;~ > 3~6g > !:~ I :A~GE ~ L3 ~'_ R_16_g_9_

R42> I ~ _470' I

1 :ANDGE ~L2~T CI4

.001 _

I

I :A~GEjLl~: ~~ ~L )~-------------~

T24

III

2

6 3

-=.l='

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•II

I

~R41180

R36180

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o

OUTPUT LEVELCONTROL

< R34120K

IOUTPUT LEVEL I

>R40180K

R37 B )4----,

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AMPLIFIER- - -- - - --,V

~rl rL.J';--1~---_+_----,I METER TUBE METER TUBE

< RIOO V21A V21B10M I I

< 2: 12AU7 2: 12AU7

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I PERCENT I ~ - / \, - R~~~

"'~"'::~") ,~.:~, r6:~o,~I~~' 10K

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Figure 4-16 Schematic Diagram of Model 608D S

Serial number 192 and above

rouTPuTl-yOLTS·...J

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p

~I R.f OUTPUT I

"NYR59-53 J4

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..... CR7~ GilA

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RF GENERATOR ASSEMBLY---.,---------

UPPER (TUBE) COMPARTMENT

:A~GE ~ L3 I~A~GE IL2 I:A~GE ILl I

FL3

GREEN

_) (_ - - - - - - - - - - - - _-I

:4500 ,

_+ -!.M~O~O~U~L~A~TI~O~N~S~IG~N~:A~L;...:====::::.:...._ -----4-'\.N",""vl--< aR82330

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-i !~:~~;I~Es:~~l :~f:-®R1,9 :r-~ :PO:~:~6AMPUFcblER

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f~ .-+b__~CL5 r ......_.I\A.I'A2V7A~ )-....l.__......;6..:JfJ--:::-~- B L....:~V__ .J 561111F r-::"lJ I~1,11 c;:; JA ~ -=-3:":'6~LF.. , :Jt \

::::;?" RANGE ~ I ':> RII3 5 4 r - - -, -L

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3:]5UllF ~RI5101=IR~iO ~~~ L_ -- J !~> i !l; --~: : ~19~ ~n > ---3 !14 1- -l~I;-- - - - - i - - - - - - - -; ~718 ~~:Z~~G)

RANSGE L4 ~ I I I I ~ I :J 1;0 I RI19 WHITE FL8 f7>.~ C65 C26 R 13 ~ t I CR':: I IN82 I 15,?0 CRJ • REiI V

IWp,~ 2000 1000, L ~ - _.J L --~ J I 1 vv ()oj.....- ........,-<H~ ~PF 1/ • r ~'...::~, -o!:- LI3 I I INe2 ' 2000

!:R109 1\ CI~7 I ~ I :J I ':>R60 IC38 I I ~100 _~ -=E-.I I '" .> I I ,100 a~~ I I

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.g6:1~ 1000 1 C

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2

7

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t

O _~L:010-2tO lC'9 : MA~~i..AI C66.J:. III1F- ;;; ~0F .I:_.005 COUPLED TO PLATE "?'

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C28 I V9 ....----+-..11.......- ....4 ....-' I.001 ,J".. 6AU6 /::: f..... GilA

r--'T'-=-----------, I ( ~ ~.¥- I

: .l.----......-----<~-+,.....:...I \-'-.."';::.:~::=: ==v=F.6:=l--...J R49 < :::~ C61 II YI g ?k623:::f:;C22 ~R48 ~ 7 470< 51111F I

-, 1-12 10 270K < I: 5MC llllF )J.f.I,F I

I II ~~ I

:~:~ - - - - RFAMPLIFIER TUNING~OMPARTMENT - -;rEJ,F~720

6.JV AC- HETEROOYNE CALl8ATOR SIGNAL

IV.-=~

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::_->-: ~L;J~i L-;_ __ I

R56I 4

.... JI M

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-4

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1 <:. R55

R54 > < 27K

120K,C35--, '?tlI

--=4 "j I 6

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C49 ,.. 6

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> lOOK

I 1I II l~L _

4. POLARITY OF CRYSTAL DIODES

+225 V DC (REGULATED)

3. POWER TRANSFORMER PRIMARY SHOWN CONNECTED FOR 115 VOLTOPERATION. TO CONNECT FOR 230 VOLT OPERATION DISCON NECTA4 FROM A I AND A5 FROM A2, THEN CONNECT A4 AND A5TOGETHER.

~

'-- - - - - - - CALIBRATOR

2. WAFER SWITCHES VIEWED FROM SHAFT END. "A" CIRCUIT NEARESTSHAFT END. "e" CIRCUIT SECOND FROM SHAFT END, SI SHOWNIN MAX, CW (EXT. MOD,) POSITION.

NOTES:I. RESISTANCE VALUES IN OHMS. CAPACITY VALUES IN MICROFARADS

AND INDUCTANCES IN MICROHENRIES UNLESS OTHERWISE SPECIFIED,

K. 1000 ....l-. GROUND

R86: 33K

_ C48

.~~

(J)? R87

-t----t--.r>-----c 1500+~C46e < (RF FIL.-.J.IO ADJ.)

-

Figure 4-16 Schematic Diagram of Model 608D Signal GeneratorI

Serial number 192 and above