HIGH VOLTAGE AND X-RADIATION PROTECTIONA potential source of x-rays is the picture tube, if the highvoltage (HV) is out of specification. When the HV is operatingproperly, there is no x-radiation. For the CA chassis family,the HV has no adjustments. A HV shutdown circuit is used toprevent excessive HV and x-ray emissions.

THEORY OF OPERATION (SHUTDOWN CIRCUIT)This circuit basically monitors the sweep pulse voltage de-rived from the sweep transformer TX3204 pins 5 & 6. Thisvoltage is rectified, and applied to a 12V zener diode ZDX3004.When the HV reaches its maximum allowed ,value (see draw-ing) the zener diode conducts, the voltage on pin 29 of thevideo processor (ICX2200) increases until it reaches the thresh-old voltage of 3.5 VDC, and shuts down the TV. If the shut-down circuit has operated, the microcontroller will preventthe TV from being turned on again, without first having tounplug the AC cord to reset the microcontroller.

TIP: Make a momentary short between the OUTPUT and GNDof the IC6002 (RESET CIRCUIT) this will reset the microcontrollerIC6000. Apply signal through the video generator or tune theTV color receiver to crosshatch pattern. Connect an accurateHV meter between the picture tube anode and chassis ground.Access Video Menu and adjust Brightness and Contrast con-trols for minimum screen luminance. Wait until, the VideoMenu or display disappear. Read HV meter.

SAFETY CIRCUIT TEST PROCEDUREEquipment required:

a) Video Generator.

b) HV DC meter (0 to 40 KV, high Z).

c) External variable power supply (0V to 200 VDC @ 5Ampsminimum).

d) 1 Giga ohm, 5%, 2W film resistor.

Before turning the TV on, connect the HV meter�s negativeprobe (-) to ground (DAG ground recommended) and the posi-tive probe (+) in the anode of the CRT. Connect a 1 Giga Ohmresistor in parallel with the HV meter. Then connect the exter-nal power supply�s negative output (-) to chassis ground, thatis, the negative lead of B+ filter capacitor, CX3420. Turn onthe TV. Apply a video signal or tune the TV to a raster pattern.Adjust the G2 potentiometer for minimum, and set the bright-ness and contrast levels to minimum. Now adjust the outputvoltage of the external power supply to 124 VDC for CA25V/27V or 130 VDC for CA32V/36V. Then start increasing thevoltage on the external power supply until the TV shuts down,and read the HV on the meter just before the voltage startsdropping.

Note: The external power supply may require a diode forblocking voltage from the chassis power supply tothe external power supply. The diode should beconnected between the positive output of the externalpower and B+ of the chassis. The cathode should befacing the B+ of the chassis. The recommended diodeis Part No. 103-00339-04A (400 V of VRRM @ 3Amps of average rectified forward current).

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CA-ii

CA Chassis Safety Guidelines

CA-iii

Preface

This manual has been designed as a supplement to the CM-151 CA/CB training manual (923-3351TRM).It provides circuit descriptions as well as troubleshooting flowcharts for both CA and CB chassis. Eachdescription includes schematic diagrams of the particular section(s) being discussed. These inclusionsrepresent a change from some recent training manuals. Moreover, this manual is divided into two distinctsections, respectively, for CA and CB chassis. Such an arrangement should prevent confusion between thetwo.

Many servicers prefer to use their training manuals in conjunction with the corresponding service manuals.As such, the schematics contained in this training supplement were drawn to be fairly generic. However, asa concession to those who desire a quick reference, tables that include part numbers of major componentshave been supplied in each applicable circuit description. Note that these part numbers should only beapplied to those sets which fall under component level repair warranty. (32� and 36� sets have a modulereplacement warranty.) Hence, when a table refers to �all models�, it can only apply with certainty to allcomponent level repairable modules. Likewise, in the troubleshooting section, flowcharts will often instructthe repair technician to replace a certain component under a particular situation. Again, such instructionconcerns component level repair sets. Still, the flowcharts provide useful information for diagnosing aproblem on component level warranty modules and replacement warranty modules alike.

Frequently, the tables refer the reader to the service manual for particular models associated with givenparts, particularly with regard to the CA chassis. This is because at the time this manual was produced,there were 81 variants of the CA chassis in the field. In any case, parts referencing is really beyond thescope of a training manual. Furthermore, it is a good idea when looking up part numbers to refer to up-to-date service information. Generally speaking, training in circuit theory and operation does not change whenpart numbers do.

Finally, be sure to take special note of the safety information supplied in this manual. General safety infor-mation is provided for both chassis on the reverse side of the front cover. High voltage protection instruc-tion for the CA chassis is located on the page following the general safety page and for the CB chassis at thestart of the second section of this manual.

CA-iv

Table of Contents

Section 1General Safety Guidelines ................................................................................... CA-iCA Chassis Safety Guidelines ................................................................................... CA-iiPreface ................................................................................... CA-iiiThis Table of Contents ................................................................................... CA-ivCA Circuit Descriptions

Power Supply ................................................................................... CA-1Microprocessor Control ................................................................................... CA-5IF Receiver ................................................................................... CA-9Video Processing ................................................................................... CA-11Deflection Control ................................................................................... CA-17Audio Development ................................................................................... CA-22

CA Troubleshooting ................................................................................... CA-27

Section 2CB Chassis Safety Guidelines ................................................................................... CB-iCB Circuit Descriptions

Power Supply ................................................................................... CB-1Microprocessor Control ................................................................................... CB-5IF Receiver ................................................................................... CB-9A/V Switching ................................................................................... CB-12Video Processing ................................................................................... CB-16Deflection Control ................................................................................... CB-22Audio Development ................................................................................... CB-27

CB Troubleshooting ................................................................................... CB-30

CA-1

Power Supply

Introduction

The CA chassis is a cold ground chassis deriving its power from a switch-mode, flyback type, powersupply. It features indirect B+ regulation, over-current protection (OCP), software controlled degaussing,necessities for Energy Star compliance, and provision for future universal power input (85VAC - 265VAC).

The switch-mode power supply, or SMPS, converts AC line power to the various DC voltages required bythe receiver. Note that there is no switch to activate or deactivate the SMPS. It operates as soon as ACline power is present. Input power demands can reach a maximum of 130 watts on 25 and 27 inch sets and145 and 150 watts on 32 and 36 inch sets respectively.

Switch-Mode Power Supply Primary Side

The receiver is protected from AC line surges by FX3401, a 4A, 250V fast-blow fuse. The AC operatingrange is between 90Vrms and 135Vrms. AC is first filtered by LX3401 and CX3402. It is then rectifiedusing a diode bridge (package DX3400 on 32"/36", discrete components DX3401 through 3404 on 25"/27"). CX3407 smoothes out the resulting DC voltage. It is from this voltage (called VDC or raw B+) thatthe heart of the SMPS, the Switch-Mode Regulator, is run. Raw B+ can run anywhere from +127VDC to+191VDC.

DX3402

DX3403

DX3401

DX3404RX3401

CX3406

C3403

CX3407

CX3404

CX3405

CX3402

B+ VDC

LX3401

CX3401EX3401

RX3400

CX3400

FX3401

3R8

DX3400

To DegaussingCircuit

<<Figure CA-1>>

Primary components of the Switch-Mode Regulator circuit include the switching transistor, QX3401; theregulator IC, ICX3400; and the chopper transformer, TX3401. The actual chopper used will depend onthe size of the set. This transformer isolates the rectifier and regulator sections, which use hot ground, fromthe rest of the CA chassis, which uses cold ground.

When line power is introduced to the set, raw B+ is supplied to pin 18 of the chopper (switch-modetransformer). At the same time a small amount of raw B+ is drawn through RX3404 into pin 2 ofICX3400. This voltage triggers the switching of a transistor internal to the regulator IC. Once this happens,current begins to alternate between flow and rest in the raw B+ winding (pins 18 and 11) of the switch-mode transformer. Alternation will occur at a frequency of approximately 25 KHz when the set is in stand-by, and near 50KHz when the set is powered up. Because of the transformer action, base drive to pin 2 ofICX3400 is from this time forward maintained by another winding on the chopper (pins 13 and 15) throughCX3416.

CA-2

CA CIRCUIT DESCRIPTIONS

<<Figure CA-2>>

Another winding from the chopper (pins 13 and 16) provides feedback to the regulation loop in ICX3400.The AC from this winding is half-wave rectified by DX3408 to supply a negative voltage to pin 1 of theregulator IC. ICX3400 is designed in such a way that it will adjust both its oscillating frequency and dutycycle to maintain -41 volts DC on pin 1. Thus as changing power demands are reflected in the choppertransformer, feedback to ICX3400 triggers a corresponding change in the regulated supply.

ICX3400

TX3401

QX3401

CX3410

RX3406

DX3406

CX3409CX3408

RX3404

RX3408RX3407

RX3403

B+ VDC

CX3411

DX3407

CX3412 CX3413

RX3409DX3408

C3418

CX3416

LX3410

B+ VDC

RX3405 CX3415

RX3410PROV

C3414PROV

RX3411PROV

DX3409PROV

B+ VDC

16

ToRegulatedB+

To+18 VSB

5

7

8

4

115

13

11

18

54321

Q-Switching

Q-Reg

Q-Limiter

DZRegR-ShuntR-Bias

R-Div2R-Div1

5

4

3

2

1

R-AntiSat

223-00028ICX3400

<<Figure CA-3>>

QX3401 serves as the Over-Current Protection (OCP) switch. If the current sensing resistor, RX3403,passes too much current to pin 4 of ICX3400 (the emitter of the internal switching transistor), the resulting

CA-3

Power Supplyvoltage at the base of QX3401 will switch that transistor on, shunting the regulator IC�s base drive toground. Such an action kills the regulator�s oscillation, thereby eliminating power generation.

Several capacitors, CX3408, CX3409, CX3410, and CX3412, are used in the SMPS to reduce EMI(electro-magnetic interference). Additionally, RX3405 and CX3415 serve as a snubber circuit, to reducepeak voltage on the collector (pin 3) of ICX3400�s switching transistor.

Switch-Mode Power Supply Secondary Side

The two windings on the secondary side of the chopper transformer generate the regulated B+ (or simplyB+) which, depending on the size of the television, will be either +124 volts DC or +130 volts DC, and the+18 volts DC. Both are present when AC line voltage is supplied to the SMPS. Hence these voltages maybe considered Stand-By (SB). The B+ supplies necessary power to the horizontal sweep and the horizon-tal output sections. It is filtered and rectified using LX3403, C3419, and D3410, and it can be measuredacross CX3420. Note that the B+ line does not have a fuse. The OCP circuit mentioned above serves toshutdown the power supply if too much current is drawn through the regulated B+ circuit.

TX3401

LX3403

LX3404 DX3411

D3410

CX3424CX3420

C3421

C3419 B+

+18 VSB

RX3428

ZDX3401 C3460

+15 VSW

R3427

R3423

C3425

OUTIN1

2

3

ICX3402

C3426

+5 VSBQ3406PROVFX3402

W3402

R3422M

PROV

L3407

R3424PROV

D3414PROV

Q3402

R3418

R3414Q3404

R3412M

Q3405PROV

R3425MPROV

R3426MPROV

W3401

L3405

CX3430C3428PROVC3429

RX3417OUT IN1

2

3

ICX3401

+9 VSW

4

1

7

5

8

Power ControlPulse fromPin 32, IC6000

+18VSW

+18VAUDIO

+5VTUNER

<<Figure CA-4>>

On the other hand, the +18 volts DC (or +18 VSB) is fused by FX3402. Rectification and filtering of the+18 VSB is accomplished by an arrangement similar to that of the B+. The resulting +18 volts DC may bemeasured across CX3424. This voltage is further broken down to provide power to various circuitsdescribed below.

CA-4

CA CIRCUIT DESCRIPTIONSICX3402 regulates from the +18 VSB to provide +5 VSB. The +5 VSB powers the microprocessor,IC6000, and the tuner, TU6000. Additionally, part of the power from the +18 VSB supplies +18 volts tothe audio circuitry (+18 AUD). The remainder of the +18VSB power is used when the set is powered up.This powered up voltage is typically referred to as a switched voltage (VSW). The +18 VSW powers thehorizontal drive amplifier. That same +18 VSW is also regulated through ICX3401 to produce a +9 VSW.This +9 volts powers the video signal processor, ICX2200, and, in stereo sets, IC1400. Finally, a +15VSW is generated from the +18 VSW using RX3428, ZDX3401, and C3460. The +15 volt supplypowers the ABL video and the variable audio output circuits.

These switched voltages turn on given a DC level from pin 32 of IC6000. This signal will of course comeon when triggered by the power on key from the keyboard or the IR detector, IR6000. The DC level at pin32 should be near +4.8 volts DC. This will drop across R3418 and switch the base of Q3402. As thistransistor turns on, it drives Q3404 into saturation and activates the switched voltages.

Degaussing Control

Degaussing is accomplished via software in the CA chassis. At turn on, pin 33 of IC6000 generates a +4.8volt DC level. After dropping through R3419, this DC switches on Q3403 to allow current flow throughthe degaussing relay, KX3401. With the relay now turned on, filtered AC line current travels into thedegaussing coil passing through the thermistor, THX3415. 760 milliseconds after power-up, the micropro-cessor sets the voltage to zero, and the relay opens cutting off AC to the coil.

KX3401

DX3405

Q3403

THX3415

+18 VSW

R34192

1

FilteredAC Line

DegaussingControl, Pin 33,IC6000

3T8 -- ToDegaussingCoil

<<Figure CA-5>>

CA-5

Microprocessor Control

Introduction

The CA chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessedusing this IC. While most of its functions will be described in terms of how they are used by other devices inthe receiver, a number of facts concerning the microprocessor and its input devices will now be presented.

The microprocessor�s job is to communicate control instructions and feedback information to and fromvarious other processors and input devices in the set. These include the video, audio, PiP, audio & videoswitch ICs, the tuner, the EEPROM, the keyboard and IR detector, and the reset IC. Some of these use adirect connection via either switch, variable pulse, or DC level for communication. Others rely on the I2Cbus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines. The first setis pins 37 and 39, and the second is on pins 36 and 38. The EEPROM and the factory setup connector,4G9, are the only devices which receive clock and data pulses from the first set.

Input Devices

The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 ofthe microprocessor. There a special algorithm interprets the pulses as the various commands they represent.The keyboard is only slightly more complicated in its operation external to IC6000. It works by varyingvoltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpretthe different voltages. Because voltage detection is used rather than active keyboard scanning, keyboardradiation is not a problem, but maintaining a +5VSB to within ±4% is critical.

R6018

R6017M

R6020M

R6019M

R6022MR6025M

R6021MR6023MR6024M

+5VSBF

R6015

R6016

R6069M

R6070M

C6042MC6043M

Pin 7

Pin 8

1

2

3

4

5

+5VSBF

L6005

C6036MR6029MC6035PROV

L6004

Pin 15

C6004

R6028

C6092M

C6003M

R6027

2K6

3

2

1

IR6000

GND

VS

VOUT

EXTERNALKEYBOARD

Keyboard& IR Input toIC6000

SW1ON/OFF

SW2CH-UP

SW3CH-DN

SW4VOL-UP

SW5VOL-DN

SW6MENU

<<Figure CA-6>>

CA-6

CA CIRCUIT DESCRIPTIONSFor those CA chassis that have the keyboard and IR detector built onto the module, the schematics areincluded. Keep in mind, however, that many of the various CA chassis have a keyboard and IR module thatis separate from the main board.

Microcontroller

VCC is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relativelylow, IC6000 is fairly demanding in terms of current. This same voltage also powers the keyboard and IRdetector. Additionally, the +5VSBF is used as analog VCC and enters the micro at pin 18.

IC6002 serves as a reset IC for the main microprocessor. Note that it comes in a transistor type package.It accurately resets the micro when SB voltage is detected. Pin 30 is the reset signal input for IC6000. Themicro enters reset state after detecting a low on pin 30 of 2µS or more.

When the micro receives a power on signal from either the keyboard or the remote, the degaussing controlpin 33 turns on the degaussing circuit for 760ms. At the same time a constant voltage level from pin 32turns on the switched voltages in the power supply.

<<Figure CA-6>>

Horizontal and vertical synchronization pulses are fed into pins 1 and 2. These provide the microprocessorthe current sweep location of the beam, which is necessary to correctly interrupt main video for various

C6012MC6013

L6001

+5VSB +5VSBF

C6017

R6037M

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

36

26 27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52HSYNC

VSYNC

AFC

FM_SD

NC

SYNC

A/D_KEY2

A/D_KEY1

NC

Y/C-SENSE

PiP_BRT

NC

CRT-PROT

MUTE

REMOTE

NC

NC

AVCC

HLF

RVCO

VHOLD

CVIN

CNVSS

XIN

XOUT

VSS

R

G

B

FB

VERT-SIZE

HORZ-SIZE

VOL

NC

AUD-SWITCH

PiPSWITCH1

AUX_SW1

NC

H/T

SCL1

SCL2

SDA1

SDA2

IDENT

RADIO/TV

DEG-CTL

POWER

CHASSIS-ID

RESET

OSC-OUT

OSC-IN

VCC

IC6000

VCC

GND

OUT

IC6002

C6016 C6056M D6001

CRY6002PROV

L6002

R6060MR6035MC6015M

C6014M

R6059M

CRY6001

R6034M

C6010M C6011M

C6008MPROVR6080

R6033MC6009

R6032M

C6007M

R6031M

PROV

C6006

C6005M

C6098

R6030L6007

+5VSBF

C6037

To IR6000

R6026

C6040M

C6092M

C6090M

C6093M

To Keyboard

+5VSBF

C6062M

R6001M

R6005M

R6012M

R6058M

D6002

R6053M

C6061M

C6079M

R6061M

C6058M

R6090M

Q6001

Q6002C6068M

R6008MR6002M

R6004MR6003M C6001M

C6024MPROV C6025M

PROV C6033MPROV

C6023M

R6082M

C6067MR6084M

C6099

Q6003C6066PROV

C6064MR6083M

R6040M

R6081M

C6057M

C6041M

C6094MPROV

R6036M

C6018M

C6046M

C6045M

C6051M

C6052M

C6053M

C6095M C6038MC6055M

FLYBACK

V-RAMPV-DRIVE

AFC

PiP-BAT

SYNC

Y/C-SENSE

CRT-PROTECTORMUTE

PWR-CTLDEG-CTL

AUX-SWITCH1PiP-SWITCH1AUD-SWITCH

VOL-CTRLHORZ-SIZEVERT-SIZE

HALFTONEFASTBLANK

B+UPG+UPR+UP

COMPOSITEVIDEO IN

EEPROM& FactorySetup Ckt

CA-7

Microprocessor Controltypes of on-screen display (OSD). Neither sync pulses come directly from the video processor where theyare first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulseline. Vertical ramp signals feed the base of Q6002. Sync is produced on the collector and fed to thevertical amplifier and through R6006M to the V-Sync pin of the micro. OSD or CC (closed captions) aresent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At those times it is necessary toblank out main video, a fast-blank (FB) pulse is sent to the video processor from pin 49 along with theprocessed RGB. An exception to this occurs when PiP is displayed. Under that circumstance, the fast-blanking pulse without RGB is sent to the video processor.

Some CA chassis feature a halftone function that dims video surrounding OSD. This halftone circuit isdescribed in the video section, but is controlled by a DC level from pin 40.

Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is re-quested by the user. Note that when OSD needs to be on the screen, such as after a channel change orduring a volume change, the OSD will have priority, and CC will mute. IC6000 also gains synchronyinformation from the composite video stream.

Pin 6 is a signal detection pin. When the tuner sends a bona-fide signal to the video processor, it separatesthe horizontal sync signal from the IF and sends it to this portion of the microprocessor. It can then be usedto determine if a certain channel is carrying an active broadcast.

Automatic frequency correction (AFC) is sent to the microprocessor via pin 3. The DC level on pin 3 tellsthe microprocessor if it needs to communicate an adjustment to the tuner to allow for clearer channelreception. The ideal voltage level here should be approximately +2.5 volts.

IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DClevel from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, theDC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver downthree seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phos-phor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.

The remainder of the input and output pins of IC6000 are adequately described in other sections of thismanual. Refer to the video, audio, and deflection sections of the CA chassis for these descriptions.

IC Location Part # NotesIC6000 221-01384-01

221-01384-02 Refer to Service Manual221-01386-01 for Corresponding Model 221-01387-01

IC6001 221-00745-04 All ModelsIC6002 221-01177A All Models

<<Table CA-1>>

CA-8

CA CIRCUIT DESCRIPTIONS

Memory

The EEPROM, IC6001, is a small but vital part of the CA receiver. This 512 byte memory chip is respon-sible for storing servicer adjustments, channel information, and user settings, even when power is removedfrom the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6.The EEPROM is powered by the +5VSBF source at pin 8.

1

2

3

4 5

6

7

8

IC6001

R6049

R6050M

+5VSBF

L6003

C6020 C6021M

1

2

3

4

5

+5VSBF

R6072R6039M

C6019M

R6046M

R6045M

R6047M

R6048M

C6047MC6048MC6049MC6050M

IDENTDATA2DATA1CLOCK2CLOCK1

R6041R6042MR6043R6044M

CLOCK2DATA2

(IC6000)3536373839

Clock & Datafor Tuner, Videoand Audio

4G9

<<Figure CA-7>>

CA-9

IF Receiver

Tuner

Cable or off-air signals are received into the television by way of the antenna jack of the tuner, TU6000.The input and output impedance of this device is 75 ohms. It provides for 181 channels (including cable).It uses +33V for tuning, +5VTune as tuner B+, +4.3V for AGC, and on some chassis +9VSW.

As with standard varactor tuners, varying voltage across an internal varactor results in a different internalresonant frequency, whereby tuning of the various channels is achieved. Control of this process is accom-plished through the I2C (serial clock and data) lines attached to pins 4 and 5 of TU6000. These transfercontrol data to and from IC6000.

AGC (automatic gain control) voltage is applied to pin 1 of the tuner from pin 3 of ICX2200. This DCvoltage varies in response to signal strength from the tuner so as to avoid signal distortion not only from lowsignal levels, but also from signals strong enough to otherwise cause clipping distortion. AGC voltage willalter the signal level accordingly.

<<Figure CA-8>>

IF Processor

Tuner IF (intermediate frequency) comes from pin 11 of the tuner. This is filtered and amplified (seeQ1200, U1200, and surrounding circuitry) before it is fed into pins 7 and 8 of ICX2200, the IF/videoprocessor (sometimes called the Jungle chip). IF consists of PIF (Picture IF), SIF (Sound IF), and CIF(Chroma IF).

+33V

+5VTune

+9VSW

ZD6001 C6032 C6031M

C6030 C6029M

L6000

CX6027 C6026M

TP6006 TP6005 IF

TP6010

C6090PROV

C6070

PROV

Clock2

Data2

TP6004

C6028

J6000M **

RF-AGC

** ONLY FOR 175-2771 TUNER

OMIT FOR 175-2771 TUNER

From Pins36 and 38,IC6000

11

10

9

8

7

6

5

4

3

2

1

TU6000

CA-10

CA CIRCUIT DESCRIPTIONS

<<Figure CA-9>>

ICX2200 powers its IF section using +9VPIF (pin 9) and +9VSIF (pin 48). The IC�s main VCC is a+9VF supply to pin 46. IF signal continues from pin 47 at nearly 2Vp-p to an FM trap where SIF isseparated from PIF. SIF reenters ICX2200 at pin 52, the limiter. From this, composite audio is developedand transmitted from pin 2 of the video processor to the audio circuitry. The remaining PIF passes throughQ1202 for de-amplification to 1Vp-p. The resulting signal, denoted TVIN, is passed to both the Jungle ICat pin 37 and pin 5 of IC2902 (refer to the jack-pack and switching section below).

AFT (automatic fine tuning) is also derived from the video processor at pin 44. This signal feeds the micro-processor, IC6000, to generate minute tuning adjustments so as to maintain optimum channel quality.

Part Location Part # NotesTU6000 175-02721 Refer to Service Manual

175-02771 for Corresponding ModelsICX2200 221-01165 All Models

<<Table CA-2>>

C

1

2

3

4

5

6

7

8

9 8

49

50

51

52

53

54

55

56NC NC

SND-OUT

RF-AGC

SIF

AGC-FIL

PIFGND

PIF-IN

PIF-IN

PIF-VCC SIF-VC

PIFTANK

PIFTANK

SIFGND

LIMITER

AUDIN

EXT-AUD

DE-EMPH

47TV/DET

46

10

11

LOOPFIL

APCFIL VCC

ICX2200 TP1248 TP1245

C1214

C1213M

TP1201

+9VSW

L1203L1200

C1215M

+9VSIF

C1216

+9VPIF

R1225 R1200M C1200M

R1201M

3

2

1

L1202

R1210M

C1205M

C1206

R1231M

TP1200

1

2

4

5

3

U1200

R1211M

C1204M

R1209M

+9VPIF

R1206M

Q1200

L1201C1202M

R1205M

R1204M

R1203M

C1201M

R1202M

IF

R1207M

R1208M C1203M

+9VSW

R1212MC1208M

C1207U1201

R1214M

C1217M

C1218M

L1204

R1215M

+9VPIF

C1209M C1210

C1212 R1213M

C1211M

Q1201

TP1202

R1216M

R1217M

R1218M

U1202

L1205

R1219M

Q1202

C2237M

R1221M

R1220M

TVIN

3

2

1

L1206

+9VSIF

C1219M

+9VSW +9VF

L1207

C1220M C1221MC1222

6

4

AGCPin 1,TU6000

CompositeAudio

4

CA-11

Video Processing

Introduction

ICX2200 has numerous duties involved in television image and sound production. As mentioned above, itprocesses sound and video IF. Additionally, it prepares NTSC video utilizing separated chroma, luma, andOSD from IC6000. Accounting for controlled preference information from the micro such as brightness,tint, sharpness, contrast, etc... the �Jungle� chip then produces this video signal as RGB which is amplifiedand sent to the picture tube. Finally, the video processor generates the very drive signals that cause thedeflection circuitry to operate and produce high voltage as well as picture.

A/V Switching

At this point, because of its interaction with the video processor, an explanation of the jack-pack switchingsection is expedient. Depending on the extra features a CA receiver has (S-VHS Video or Y/C, PiP), thechassis will have two switching ICs, IC2901 and IC2902. IC2902 is the PiP switching IC. The first

12

11

10

9

8

7

6

5

4

3

2

1

CH-2

CH-1

IC2901

12

11

10

9

8

7

6

5

4

3

2

1

CH-2

CH-1

IC2902

C2908

R2901M

R2915M

C2911 C2904

+9VSW

R2919M

R2918M

R2922M

Q2902

C2915M

C2913

C2910

C2912M

C2916

C2917M

C2914

R2920M

R2921M

C2906

C2900

C2909

W2903

J2902M

R2902M

ZD2901

R2923M

R2907

C2902M

C2918L2901

C2903MR2905M

C2918

R2917M

ZD2903

R2914

R2916

ZD2902

R2908

R2910M R2911

R2909

C2907M

R2912

Ext-LExt-RVM Out-LVM Out-R

CMChroma-CombAux Switch1Ext Video

Y/C SensePiP Switch1TVINVIN PiP

J1External

LeftExternal

RightVariable Monitor

Out - LeftVariable Monitor

Out- RightVideo-In S-VHS

12 11 9 8 7 6 5 124 310

<<Figure CA-10>>

CA-12

CA CIRCUIT DESCRIPTIONSswitching channel of this IC switches the PiP between external and internal video sources based on the PiPSwitch1 signal (pin 4, IC2902) from the microprocessor. The internal video signal, denoted TVIN, is thesame signal as the one entering pin 37 of ICX2200. Whichever signal is selected is sent as VIN PiP to thePiP module through pin 10 of the PIPA1 connector. The second switching channel of IC2902 allowsselection between composite video input and S-Video input. While normally it defaults to composite video,its switching action is based on the presence of S-Video. The output of this switch feeds the external side ofthe PiP switch.

IC2901 is referred to as the main switching IC. Both switching channels of IC2901 are controlled by theAuxSwitch1 input from the microprocessor. It is tempting at first glance to assume that this IC switchesbetween external and internal video sources. However, ICX2200 actually handles that process internally.Rather, IC2901 switches the between the external source to be viewed (composite or S-Video) on switch-ing channel 2. The output from this channel goes to pin 39 of ICX2200, the external video input. Channel1 switches between the internally separated chroma signal and the S-Video chroma signal, and feed itsoutput back to pin 45. See below for a further description of video separation.

Video Development

For video processing, ICX2200 will switch between tuner IF, which as discussed above enters the IC at pin37, or an external video source, which enters the Jungle chip at pin 39. Switching between these will bedirected by the microprocessor via the I2C bus entering ICX2200 on pins 27 and 28. The selected signal isemitted from the switched video out pin (41) as composite video. This signal is sent to the microprocessorand the glass comb-filter, DL2200.

The purpose of the comb-filter is to separate chroma from luma. Its superiority to conventional filtering andseparation schemes is that it reduces cross talk between chroma and high-frequency luma. Historically, setswithout this feature were prone to have rainbow effects on objects whose luminance frequency approachedthe 3.58 MHz color subcarrier. (Note that this frequency is established by CR2201, the color crystal in CAchassis.) The result of the comb-filter�s operation is that cross color distortion is minimized for much morehighly detailed objects.

Composite video enters the comb-filter on pin 2. Luma is produced on pin 5 and is fed to pin 43. A3.58MHz trap (C2229M, L2201, & R2245M) removes any residue chroma. Separated chroma exits thecomb-filter at pin 3. In sets that utilize IC2901 for jack-pack switching purposes, chroma from the comb-filter is sent to pin 5 and exits at pin 8. This signal is then denoted by CM, and is passed back to the videoprocessor via pin 45. (In sets that do not use IC2901, chroma passes directly to pin 45.) A band-passfilter (C2232M, R2253M, & L2202) eliminates any remaining luma.

Once inside the Jungle IC, luma is processed with numerous factors including contrast and brightness.Brightness and contrast information from the beam current passes into pins 36 and 38 from the circuitryconsisting of Q2204, 2205, and 2209. ICX2200 responds to this information by limiting (when necessary)contrast and brightness to the RGB outputs. Basically, the ABL responds to current from pin 8 of thesweep transformer, TX3204. D2204, R2235, and C2220 make this signal positive. It is then inverted byQ2205 and smoothed as it passes to Q2204. As beam current approaches 1.5 mA (1.3 mA on 25�, 0.9mA on 19�/20�) Q2209 starts to turn on and shunts excess current to ground. In addition to controlling the

CA-13

Video ProcessingRGB output, this circuit helps to prevent blooming. Excessive current draw in the picture tube will lowervoltage and hence decrease beam acceleration. This results in an increase of the sweep. Without ABL, theblooming effect is usually seen when very bright images appear on the screen. ABL should prevent this andextend the life of the picture tube.

<<Figure CA-11>>

Before sending processed RGB (red, green, & blue) outputs to the picture tube, ICX2200 integrates anyOSD (on-screen display), CC (closed caption), and PiP (picture in picture) into the video. At a particularpoint in the television�s scan across the picture tube, where the video is to display an OSD object, a fast-blanking (FB) pulse is sent from the microprocessor to the video processor at pin 14. This pulse of courseblanks the main screen video so that OSD can have precedence. Simultaneously, processed RGB from themicroprocessor enters the Jungle chip at pins 15, 16, & 17. This video fills in the blanked portion to be putonto the main screen.

Picture-in-Picture

A few notes concerning PiP are noteworthy here. First those sets that have PiP will not be able to producevideo without the PiP module installed unless the PiP section is jumpered out. J2201M, J2202M, W2203,and W2204 accomplish this. PiP signal enters the PiP module at pin 10 of connector PIPA1. This signal isconverted into RGB by the PiP processor and sent on to RGB OSD inputs of ICX2200. Pins 2 and 3 of

R2252M

C2235M

C2232M R2253MPROVL2202

C2236M R2254M

C2233MPROV

+9VSW

L1207

+9VF

C1220M C1222TP1203

+9VF

R1223M

C1223M C1224 R1224M

R1222M

CM

AFC

C2231

C2229M L2201 R2245MR2244M C2232

C2253 PROV

R2251

C2228M

1

2

3

4

5

DL2200

R2246M+9VSW

R2248M

W2206

C2230

R2250M

R2249M

Q2206

R2247M

C2227

W2207

Q2208

R2261M

R2262M

+9VF

R2260M

R2243M

C2224

Q2211PROV

+9VSW

R2270

W2200

C2225

R2242M

+9VFC2223

C2222 C2221

R2239M

R2236M

D2205 D2202

Q2209

R2265M

C2241R2263

R2264

+15VSW

R2237M

Q2204

+15VSW

R2241M

C2218

R2240M

R2234M

R2230MC2219

D2203

R2232M

Q2205R2238M

+15VSW

D2204

R2235

R2233

C2220

ABL

12 45

44

43

42

41

40

39

38

37

3621

13

14

15

16

17

18

19

20

CIN

AFT

YIN

DC

VSW-OUT

BLK/DET

VIN

ACL

TV-IN

ABL

VCXO

GND

FBLNK

ROSD

GOSD

BOSD

D-VCC

ROUT

GOUT

BOUT

ICX2200

VERTICALABL

EXT-VIDEO

COMPOSITEVIDEO-OUT

TVIN &AMP CKT(Pin 47)

CHROMA-COMB

CA-14

CA CIRCUIT DESCRIPTIONSthe PIPB1 connector provide sync to the PiP processor. Pins 9 and 10 of the same connector allow I2Cbus communication between the PiP board and the microprocessor. PiP brightness however is controlledfrom pin 11 of the microprocessor. This controls the bias of Q2210, which varies a DC level on the OSDinput lines to ICX2200.

CR2201C2202MR2269M

C2242M

C2203

C2204

C2205

D2210

D2211

D2212

C2207

C2206M

R2210+9VSW

R2771PROV

C2239R2268M

Q2210

+9VSW

R2267M

PiP Brt

W2204

W2203

J2202M

J2201M

1 2 3 4 5 6 7 8 9 10

R2202M

C2240

R2201MR2205M

R2203M

R2207M

R2204M R2206M R2208M

PiP+SW

FASTBLANK

G+UP

B+UP

R+UP

1 2 3 4 5 6 7 8 9 10+9VSW +5VTuner

FLYBACK

VRAMP

SCL

SDAR2213M

R2218M

R2222M

R2256MD2207

R2257MD2208

R2258MD2209

R2255

Q2207

C2240MPROV

HALFTONE

Q2201

Q2202

Q2203

R2209MR2215MR2219M

1

2

3

4

5

R2221MR2217MR2211M

C2238M

12 45

44

43

42

41

40

39

38

37

3621

13

14

15

16

17

18

19

20

CIN

AFT

YIN

DC

VSW-OUT

BLK/DET

VIN

ACL

TV-IN

ABL

VCXO

GND

FBLNK

ROSD

GOSD

BOSD

D-VCC

ROUT

GOUT

BOUT

ICX2200

PIPA1

PIPB1

2C5

<<Figure CA-12>>

After PiP or OSD RGB enters the Jungle IC, it is combined with processed luma and chroma and then exitsICX2200 as main video for the picture tube. Red, Green, and Blue outputs are found on pins 19, 20, and21. Some CA receivers have a halftone circuit that taps off these lines. When Q2207 is switched on by asignal from the microprocessor, a limited amount of RGB signal is shunted to ground. The on-screen effectof this is a slightly dimmed video. This halftone signal is output in such a way to appear as a darkened buttransparent window surrounding the OSD.

Video Amplification

Before being fed into the CRT socket board via connector 2C5, RGB is pre-driven by Q2201, Q2202,and Q2203. The resulting signals are then sent to the main color driver transistors, Q5101, Q5102, andQ5103. These transistors have a high 300V collector to emitter breakdown voltage and a low collector tobase feedback capacitance (less than 3pF). Additionally, the series-parallel arrangement of both theiremitter and base circuits involving both capacitors and resistors allow for improved high and low frequencyresponse. The cutoff frequency of these drivers is 70 MHz. R5103, 5110, and 5119 from base to collectorhelp to increase bandwidth response of the drivers. These provide negative feedback from the output anddecrease gain. As gain decreases however, bandwidth response increases. The driver transistors are

CA-15

Video Processingpowered by the +215V source derived from the sweep transformer, but the actual DC voltage at thecollectors will be lower (+130 volts is a good ballpark figure) because of the resistors RX5104, 5111, and5122 and variations in the drive signal.

<<Figure CA-13>>

The emitter circuits of each driver are attached not to ground, but to a reference voltage of about +3V. Thisreference voltage is established by R5114 and D5101 and serves to set a black level for the cathodesaround +165 volts. The reference voltage must be relatively noiseless, so C5107 is used to eliminate anyinterference.

A number of the CA chassis provide an afterglow cutoff circuit on the CRT socket board. This circuitmakes use of the fact that with respect to the picture tube, G1 is the ground. Because C5107 takes arelatively long time to discharge, there is the possibility that the picture tube could continue producingelectronic emissions for a short time after the receiver is turned off. The afterglow cutoff makes use ofpower from the filament voltage (pin 4, connector 5F2). When the receiver turns off, the loss of this voltageturns off Q5104. This allows for a brief moment the G1 cathode to become more positive, leaving lesspotential on the other cathodes from any remaining voltage across C5107. C5110 determines the dead timeon response, and C5111 determines the rise time of the G1 voltage, both of which are between 10 and 30milliseconds.

1

12

11

109

8

7

65

4

CRT1

R5128PROV

W5101

1

2

3

4

5

Q5101R5101M

C5102M

R5102M

R5103

Q5102

R5108M

C5105M

R5109M

R5110

Q5103R5117M

C5108M

R5118M

R5119

RX5104L5101

C5101

RX5111

RX5122

R5115

R5107

R5123

+9 VSW

R5105M

R5106M

C5103M

R5112M

R5113M

C5106M

R5120M

R5121MC5109M

D5101 C5107

R5114

1

2

3

4

D5102PROV

+215V

R5127

C5111 L5102

C5110PROV

R5124MPROV

Q5104PROV

R5125PROV

R5126

L5103

R5116

C5104

DAG

+215V

Blue

Red

Green

G2

G1

BLUE

GREEN

RED

G2 Wireto Sweep

2

21

2

2

1

1

2

2

5F2

5C2

2

CA-16

CA CIRCUIT DESCRIPTIONS

Deflection Processing

The last portion of the video processor to be discussed is the deflection section. This is the part of the ICfrom which the vertical and horizontal deflection signals are derived. A critical power supply to this sectionis the +9VSW which feeds pin 26. Pin 24 emits the V-Ramp signal, from which both vertical sync for themicroprocessor and vertical drive for the vertical amplifier are developed. Refer to Q6002 in the micropro-cessor circuit for this process. Horizontal drive comes from pin 32. This ultimately drives the horizontaloutput transistor, which provides both horizontal deflection and power for the sweep transformer. Pin 31provides the sync pulse output to IC6000. This signal is really the horizontal sync pulse separated from therest of the video signal. It allows the microprocessor to determine whether or not the receiver has a validsignal. The flyback pulse is input to pin 30, thus allowing sweep feedback to the video processor�s deflec-tion section.

29

30

31

32

33

34

3522

23

24

25

26

27

28

VPULSE

NFB

VRAMP

VSEPFIL

HVCC

SCL

SDA

DGND

32FH

HAFC

H-OUT

H-SYNC

FLYBACK

SHUTDOWN

ICX2200

C2213M C2214M R2224MC2212MPROV

R2223

R2220

C2211MPROV

C2208

C2209 C2210M

R2216

+9VSW

R2212M

VRAMP

CLOCKDATA

R2225M

C2215M

D2201

R2226

C2554 PROV

CR2202R2231M

R2229M

C2217M

C2216

R2227M

FLYBACKSHUTDOWN

H-SYNCH-DRIVE

<<Figure CA-14>>

High-Voltage Protection

The last terminal of note here is pin 29, the x-ray protection/shutdown pin. If the potential at this pin risesabove +3.5 volts DC, the video processor will automatically clamp the horizontal output signal, shuttingdown the receiver. In the event that this occurs, the microprocessor will have to be reset before the televi-sion can be powered up again. Voltage at pin 29 is based on the voltage output from the flyback. Highvoltage shutdown will correspond with an over-voltage in the picture tube, which could otherwise begin toemit x-radiation.

CA-17

Deflection Control

Introduction

After deflection control signals are produced by ICX2200, they need to be modified and amplified beforethey are output to the deflection yoke. The CA chassis accomplishes this necessity for 25� to 36� televisionsets through the sweep transformer and the surrounding horizontal and vertical deflection circuitry.

Horizontal Drive

The Horizontal Drive (H-Drive) circuitry exists to control the drive signal to the Horizontal Output Transistor(HOT) as well as provide deflection to the horizontal yoke. Typically H-Drive operates at 15.734 kHz. Asit passes through the driver circuit, H-Drive signal is amplified to provide a sufficient signal to the HOTwithout causing it to go into saturation, thereby preventing distortion of the drive signal. H-Drive is pro-duced at pin 32 of the Video processor (ICX2200) and is passed to the drive circuit through R2227M, asurface mounted resistor. The signal enters the base of Q3201 which is directly coupled through its emitterto Q3202. Finally, the signal passes from the collector of Q3202 to the Horizontal Driver Transformer,TX3205, where voltage-to-current conversion and proper waveshaping occurs.

1

3 4

5

6

TX3205

C3206

QX3203

LX3202

CX3212

C3204Q3202

C3203

R3205

R3204 CX3205

RX3207

+18 VSW

R3203

C3202Q3201

C3201

R3202M

R3201M

H-Drive fromPin 32, ICX2200

Flyback Line toPin 30, ICX2200

H-Output toFlyback & Yoke

<<Figure CA-15>>

Flyback Transformer

From here, the signal switches the HOT (QX3203) on to provide a current shunt for the sweep transformer,TX3204 and the horizontal yoke. This switching alternately passes then blocks the B+ voltage providedthrough the primary winding of TX3204 to the collector of the HOT. The changing magnetic field in thesweep transformer caused by this action generates the high voltage (HV). This high voltage should normallybe between 26 and 30 kV. The particular value will correspond to the size of picture tube in the set. G2(screen control) and Focus voltages are tapped from a portion of the same winding that HV is derived from.As usual G2 and Focus may be adjusted by pots on the sweep transformer. These run to the CRT socketboard.

CA-18

CA CIRCUIT DESCRIPTIONSA number of secondary voltages are also provided by the sweep transformer�s action. Particularly, +215volts is supplied from pin 2 to the Video Output circuitry for driving color. In addition, +35V and +25V aresupplied, respectively from pins 6 and 9, for horizontal width and pincushion control circuitry (when neces-sary) and for vertical amplification circuitry. Filament voltage is also supplied from pin 7 into pin 1 ofconnector 2F5. Two other signals from the flyback are the ABL (pin 8) and the flyback pulse derived frompin 6. Refer to the video processor section for an explanation of these signals.

<<Figure CA-16>>

High Voltage Shutdown

Another winding from the flyback is used for high-voltage shutdown, commonly referred to as x-ray protec-tion. Activation of the HV shutdown circuit will occur when it detects a 4 to 6 kV increase in the high

From Flyback DX3006

CX3007

CX3003

RX3013PROV

RX3022

ZDX3004

RX3016

RX3015PROV

RX3008

DX3005

RX3009M CX3004

RX3010M

RX3211

DX3252CX3254

CX3253

+35V

To ShutdownPin 29, ICX2200

<<Figure CA-17>>

GND

G2

FOCUS

E

HV

TX3204

CX3207PROV

RX3209

B+ DX3201

C3209

RX3208

+215V

CX3208

+25V

D2104

C2112

C2111

RX2124

ABL

RX3217

RX3210APROV 1

2

3

4

+215 V

RX3211

CX3212

RX3212

DX3204

C3219

+35V

DX3252

CX3254 CX3253

CX3207A

RX3216

+33V

FlybackPulse

To HV Shut-Down Circuit

To VideoOutput

2F5

6

9

7

5

8

3

2

1

H-Output

CA-19

Deflection Controlvoltage. The HV shutdown circuit utilizes a rectified DC voltage across CX3003. This voltage is applied toa zener diode, ZDX3004, through a voltage divider consisting of RX3013, RX3015, RX3016, andRX3022. The actual value of the zener will vary according to screen size. When this DC voltage becomeshigh enough, the zener begins to conduct. The resulting voltage can be metered at pin 29 of ICX2200. Ifthe voltage in the shutdown pin is above +3.5 volts, the IC�s internal shutdown circuitry will trigger anddeactivate all horizontal signal from the IC, thereby shutting off the set. In this case, the microprocessor willhave to be reset before the television can be powered on.

Width and Geometry Correction

Width and east/west pincushion correction circuitry may be found on receivers with 27 - 36 inch picturetubes. Smaller sets have pincushion correction preset in the windings of their deflection yokes. Otherwise,width is controlled in the CA chassis digitally through the microprocessor, IC6000, using an internal pulsewidth modulator. The width control signal is emitted from pin 47 of the microprocessor and is supplied toC3250. This operation is very similar to the vertical size adjustment. The resulting DC voltage effects thebiasing of transistor Q3250, thereby changing the current in coil LX3201 and ultimately altering the width.

<<Figure CA-18>>

R3252

C3250

Q3250

R3255

Horz Size Pulse

RX3256

R3253

QX3251

R3257M

TP3200

R3259

CX3251

LX3201

DX3250DX3251

CX3252 CX3216

CX3256

C3217

H-Output from QX3203

LX3262

H Yoke

+35V

RX3215 CX3215

DX3203

RX3214 CX3218

C3255

R3258

W3203

W3200

W3201

W3202

Vertical RateDrive

VerticalParabola

The pincushion correction is accomplished using diode modulation. Key components of this circuit includethe width coil, LX3201; the horizontal yoke; CX3216 and CX3252; CX3217, used for S-correction;LX3262, for linearity; DX3250 and DX3251 as dampers; and QX3251 and CX3251, used for amplifyingthe vertical parabola waveform. This circuit uses the parabolic waveform from IC2100, the vertical ampli-fier, to shorten the horizontal scan lines on each end of the vertical trace. As the vertical trace is near itsextremes, voltage across CX3251 is increased. The result is a lower net voltage across the horizontal yokecoil which translates to less beam deflection. Conversely, when QX3251 modulates a lower voltage acrossCX3251, particularly when the vertical scan is closer to the middle of its trace, deflection is increased. The

CA-20

CA CIRCUIT DESCRIPTIONSresulting waveform for yoke current is a sawtooth with rounded peaks.

Vertical Amplification

Most of the vertical signal amplification is performed by the vertical amplifier, IC2100. This IC contains apower amplifier, a ramp generator, and a flyback generator and is supplied by +25 volts to pin 10. Theinitial vertical drive signal which should run at 60 Hz is developed from ICX2200, the video processor. Pin24 of ICX2200 is the vertical ramp (VRamp) source. This signal is inverted by Q6002 and sent as verticalsync to pin 2 of IC6000. It also travels as vertical drive to pin 3 of IC2100 through R2101. The verticaloutput signal to the yoke comes from pin 1.

<<Figure CA-19>>

RampGenerator

VoltageRegulator

PowerAmp

BufferStage

ThermalProtection

FlybackGenerator

R31

2

3

4

5

6

7

8 9

10 11

ClockPulse

IC2100

R2101

R2104

C2130MC2101

R2103

C2102

R2106M

R2107M

R2105

C2103

R2108

R2109M

R2110M

R2111M

CX2105

DX2101 CX2110

RX2117

C2106

R2118 R2119

R2114

R2112M

R2113

RX2115 RX2116

C2104 C2108

C2107

+25 V

Vertical RateDrive for PinCorrection

To CRTProtectionCircuitry

VerticalOutput

VerticalABL

VerticalSize

VerticalDrive

Vertical size is also amplified within IC2100. IC6000 controls vertical size using a pulse width modulatedsignal emitted from pin 48. The signal generates a DC voltage across C2101. This DC controls verticalheight using circuitry inside IC2100. As the width of the pulse changes, a corresponding change occurs inthe DC level. In this manner, vertical size may be controlled in the on-screen servicers menu.

CA-21

Deflection ControlCRT Protection

CRT protection is provided for the CA in circuitry off the vertical amplifier. In case of a damaged IC2100or a shorted CX2107 for example, this circuit will prevent damage to the CRT by shutting the microproces-sor off. In turn, this action shuts down the television receiver. The circuit is composed of C2109, DX2102,DX2103, R2120M, R2121, R2122M & R2123. Pin 11, the pump-up, of IC2100 emits a pulsing wave-form. DX2102 rectifies this waveform to a DC voltage across C2109. After passing through the voltagedivider network formed by R2121 and R2122M, the voltage can be found on pin 13 of IC6000 and shouldmeter between +3.6 and +5.1 volts. Should the voltage be outside this range, CRT protection will trigger.If the CRT protection circuitry is triggered at power on, the television will turn off in 3 seconds. If thisoccurs, it will be necessary to reset the microprocessor before the television will turn on. Resetting themicroprocessor may be accomplished by removing AC to the set for a couple minutes.

R2120M R2121 R2123

R2122MC2109

DX2102

DX2103

+5 VSB

To CRT ProtectionPin 13, IC6000

Pin 11,Vertical Amplifier,IC2100

<<Figure CA-20>>

Part Location Part # NotesTX3204 095-04372-01 Refer to Service Manual

095-04601-01 for Corresponding ModelsQX3203 121-01383 All ModelsIC2100 221-00992-01 All Models

<<Table CA-3>>

CA-22

CA CIRCUIT DESCRIPTIONSAudio Amplification

There are three audio circuit configurations used in the various CA chassis: mono, stereo, or MTS (Multi-channel Television Stereo). While few CA receivers are monophonic sets, the mono audio circuit bearsmentioning due to the fact that it is used in each of the three circuit variations.

IC804, the audio amplifier IC and heart of the mono audio circuit, is capable of both mono and stereo audioamplification. IC804 has dual audio inputs (pins 2 and 5) and, naturally, dual outputs (pins 10 and 7).These outputs drive 8-ohm, 5-Watt speakers. The audio amplifier utilizes +18 volts audio (+18 AUD) as itspower supply on pin 9. Its characteristic voltage gain is 50 dB. However, to eliminate potential noiseproblems, R854M and R864M are used in conjunction with feedback capacitors C852 and C862 to limitvoltage gain. Such an arrangement allows use of a higher power audio signal that is less prone to noiseinterference. Maximum output to the speakers should not be more than 3 Watts. Pin 3 of IC804 connectsthe Mute line from pin 14 of the microprocessor to the audio circuit. A high signal on the base of Q800 willturn that transistor on, lowering voltage on pin 3 and causing the amp IC to mute the audio.

1

2

5

6 4 8 7

103 9IC804

R861MC861

R862M C865MR852MC855MC852

R854M

R864M C862

C843

+18VAUD

W140

C842 C841

Q800

Mute

1

2

3

4C854

C864

C853

C863

R853

R863

R843

R851M *C851*

Left Audio*(MTS orStereo Only)

To TVSpeakers

9S4CompositeAudio or RightAudio

<<Figure CA-21>>

When IC804 is used as a mono amplifier, composite audio comes through C861 into pin 2. When used in astereo or MTS receiver, pin 2 serves as the right audio channel input, and pin 5 as the left. C861 and C851(for non-mono sets) are used to pass audio but block any DC. Surface mounted capacitors, C855M andC865M, are used to set the gain cut frequency to approximately 13 kHz. Voltage dividers consisting ofR861M and R862M for the right channel and R851M and R852M for the left channel limit the maximumsignal input to 42 mVrms. Maximum output from the stereo processor is normally 490 mVrms, whichwould be too high an input for IC804.

CA-23

Audio DevelopmentIn the mono circuit, composite audio is fed directly from pin 2 of ICX2200 into the audio amplifier circuit.However, on stereo and MTS models, composite audio is fed into IC1400A or IC1400 respectively. Herethe composite sound can be separated into left and right audio channels.

Stereo Processing

In stereo receivers, IC1400A receives composite audio through C1436 into pin 11. Because the 490mVrms composite audio signal from ICX2200 is too high for the audio processor input, the voltage dividerconsisting of R1421M and R1422M limit the signal to 245mVrms. This audio processor is controlled bythe microprocessor via serial clock and data lines connected at pins 3 and 4. IC1400A is powered by the+9VSW at pin 16. Its right and left channel output exit the IC at pins 1 and 2.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

LSOUT-R

LSOUT-L

SDA

SCL

DGND

MAININ

MAINOUT

PCINT1

PCINT2

PLINT

COMPIN

VGA

IREF

GND

SAPTCVCC

SUBOUT

STIN

NDISETC

SAPOUT

SAPIN

VE

VEWGT

VETC

VEOUT

VCAIN

VCATC

VCAWGT

NC

NC

IC1400A

C1415R1405M

C1414

C1417

C1419

C1422R1407M

C1424R1408M

C1428

C1426

C1427

+9VSW

C1433M C1430

R1425M

C1421

C1420R1406MC1416

C1425

R1404M

C1413

R1422M

C1436 R1421M

C1418

C1435M

PROV

C1434MPROV

R1401

R1402

To AudioAmp IC

Clock &Data Lines

CompositeAudio In FromICX2200, Pin 2

<<Figure CA-22>>

External audio input on the stereo chassis is passed to the audio amplifier via IC1401, a microprocessor-controlled switching IC. This IC is powered by the +9VSW at pin 9. When the external inputs are presenton a receiver, processed audio from IC1400A will come into the switching IC at pins 5 and 12. External(or auxiliary) audio enters the switching IC at pins 7 and 10. If an auxiliary source is detected by IC6000, asignal from pin 44 of the micro will trigger pins 2 and 4 of IC1401 to switch from internal to external audioinputs. Whichever audio source is selected will be passed from pins 8 and 11 to the volume controlIC1402.

CA-24

CA CIRCUIT DESCRIPTIONS

<<Figure CA-23>>

IC1402 is powered by the +18AUD at pin 4. Pins 5 and 8 receive the audio input, while the output forright and left channels come from pins 1 and 3 respectively. This volume IC is controlled by a DC levelfrom pin 46 of the microprocessor. Pin 46 emits a pulse width modulated signal that is rectified andsmoothed by D1401, R1420M, and C1438. The resulting DC voltage is applied to pin 7 of IC1402. Thisvoltage will vary from +0.5 to +5 volts DC. The gain of this IC is 12dB.

IC Location Part # NotesIC804 221-00598-01 All ModelsIC1400 221-01127 MTS ModelsIC1400A 221-01382 Stereo ModelsIC1401 221-01171 Stereo ModelsIC1402 221-01380 Stereo Models

<<Table CA-4>>

12

11

10

9

8

7

6

5

4

3

2

1

CH-2

CH-1

IC1401

+9VSW

1

2

3

4 5

6

7

8

IC1402

C1423

C1437

+18AUD

R1417

ZD1405 C1439

C1455

J1406M *

C1456

C1429

J1407M *

C1438

R1420M

R1419M

R1418M

+5VSBF

D1401

R1418

R1413

R1412

C1409

C1410

L RAudio Outputto IC804

* For Stereo Chassisexcluding 9-2064, 2065

Provisional on 9-2064, 2065

Audio SwitchPin 44, IC6000

External Audiofrom Jack Pack

Left & RightStereo Audio(Pins 1,2, IC1400A)

Volume ControlPin 46, IC6000

CA-25

Audio Development

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

2425

36

26

27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48 BASSL2

TRE-R

TRE-L

SURRIN

SURROUT

LSOUT-R

LSOUT-L

NC

SDA

SCL

DGND

SAD

MAININ

MAINOUT

NC

PCINT1

PCINT2

PLINT

COMPIN

VGR

IREF

GND

SAPTC

VCC

BASSL1

BASSR2

BASSR1

SURRTC

TVOUT-L

TVOUT-R

AUX2-L

AUX2-R

AUX1-L

AUX1-R

VLTC

VLDC

VCAWGT

VCATC

VCAIN

VEOUT

VETC

VEWGT

VE

SAPIN

SAPOUT

NOISETC

STIN

SUBOUT

IC1400

C1401M

C1402M

C1404M

C1416

C1435MPROV

C1434MPROV

R1401 R1402

R1425M

C1421

C1420R1406M

C1418

C1436

C1413

R1404M

C1425

R1421M

R1422M

+9VSW

C1433MC1430

C1403M

C1406M

C1431M

C1409

C1410

R1412R1413

R1409M

C1432

C1415

C1414

R1405M

C1417

C1427

C1426

C1428

C1419

C1422

C1424

R1407M

R1408M

ExternalAudio In

CompositeAudio In FromICX2200, Pin 2

Clock &Data Lines

To Audio &External Amps

MTS Processing

For MTS chassis, IC1400 serves as the sound processor. It features mono, stereo, or SAP settings. Italso features adjustable bass and treble levels, balance adjustment, sound-right audio limiting, front surroundsound, and speaker cut-off. Furthermore, whereas internal and external source switching is accomplishedby a separate switching IC for the stereo sets, the MTS is capable of internally switching between varioussources.

<<Figure CA-24>>

IC1400 is powered by the +9VSW at pin 24. Composite audio enters through C1436 at pin 19. Thissignal is reduced by a voltage divider consisting of R1421M and R1422M. I2C bus control (serial clockand data) from the microprocessor enters the MTS processor at pins 9 and 10. Information on these linescontrols those adjustments as described above as well as the volume. Right and left channel auxiliary inputfeeds into pins 39 and 40. Audio outputs come from pins 6 and 7 and feed the amplifier circuit in themanner described above.

CA-26

CA CIRCUIT DESCRIPTIONSExternal Audio Output

The output pins here also feed the variable audio output circuitry. This common emitter amplifier has a gainof 12 dB. Q1402 and Q1403 are used to amplify left and right channels respectively. Power for thisamplification stage is provided by Q1401, which uses the +15VSW. To reduce popping on the monitors,the switching of Q1401 is briefly delayed by an RC network formed by R1440M and C1440.

<<Figure CA-25>>

Q1401

+15VSW

R1440M

R1441M

C1440

Q1402R1442M

R1443M

R1444M

R1445M

R1446

C1441M

C1443

C1442

J1402MPROV VM-OUT-L

Q1403R1447M

R1448M

R1449M

R1450M

R1451

C1444M

C1446

C1445

J1450MPROV

VM-OUT-R

L(7)

R(6)

Stereo Signalsfrom IC1400,Pins 6 & 7

CA-27

Flowcharts

Start1. No Power

Plug receiverinto AC source.

ReplaceFX3401.

ReplaceFX3402.

ReplaceTX3401.

Replace ICX3400,QX3401, DX3406,DX3407, DX3408.

ReplaceICX3402.

Yes

No

No

No

No

No No

No

Yes

Yes

YesYes Yes

Yes

Yes

ReplaceIC6000.

Check Q3404,Q3402.

ReplaceICX3401.

ReplaceICX2200.

Refer to shutdowntroubleshooting.

No

No

No

No

Yes

Yes

Yes

Yes

Is ACconnected?

Does FX3401conduct?

Is B+ presentat CX3420?

Does FX3402conduct?

Is QX3401shorted?

Is pin 3,ICX3400

switching?

Is +18VSBpresent across

CX3424?

Is +5VSBpresent across

C3426?

Does pin 32,IC6000 emit aDC pulse at

startup?

Is +18VSWpresent across

CX3430?

Is +9VSWpresent across

C3429?

Is Horz & Vertdrive presenton pins 32, 24of ICX2200?

CA-28

CA TROUBLESHOOTING2. Shutdown

Start

Does the setpower up formore than 2seconds?

Does the DClevel at pin 29,ICX2200 rise

above 3.5 volts?

Checkmicroprocessor

ciruitry.

No

Yes

Check HV-shutdown circuit,

sweeptransformer.

Does the setshutdown afterjust 3 seconds?

Check IC2100 &CRT protection

circuit.

Yes

Yes

No

No

Is B+ running ata constant DC

level?

ReplaceICX3400

No

Yes

CA-29

Flowcharts3. No Tuning Start

Are all tunervoltages

present? (Referto schematics.)

Check tunerpower supplies.

Is IF present atpin 11, TU6000?

Does changingthe tuner fix the

problem?

Check clock anddata lines.

Replace IC6000if clock & data

lines OK.

Is IF present atpins 7, 8,ICX2200?

Check IF line.Replace Q1200,

U1200 ifnecessary.

Is IF present atpin 47,

ICX2200?

Does Q1201 testOK?

ReplaceICX2200.

Replace Q1201

Refer to No Audio and NoVideo Troubleshooting.

Yes

No

No

No No

No

No

Yes

Yes

Yes

Yes

CA-30

CA TROUBLESHOOTING4. No Video Start

Is raster presenton the screen?

Is 1.07 kVp-psignal present oncollector of HOT?

Is regulated B+present across

CX3420?

Check powersupply.

Check TX3204.Check HOT andH-drive circuit.

Is there video atpin 37, ICX2200?

Check Q1201,Q1202

Is compositevideo present onpin 41, ICX2200?

ReplaceICX2200.

Is 0.76 Vp-p lumasignal present atpin 43, ICX2200?

Check Q2206and/or DL2200.

Are RGB signalspresent on pins3-5, connector

5C2?

Are Q2201, 2202,2203 OK?

Replace Q2201,2202, 2203.

Is +215 VDCpresent across

C5101?Check TX3204.

Check G2adjustment.

Yes

No

Yes Yes

Yes

Yes

Yes Yes

Yes

Yes

No No

No

No

No

No

No

No

CA-31

Flowcharts

Check audiopower supply.

Is +18AUDvoltage presenton pin 9, IC804?

Start

Does Q800 testOK?

Does DC levelchange at pin 14,

IC6000, whenspeaker cut-off is

toggled?

Is compositeaudio present atpin 2, ICX2200?

Is compositeaudio present atComp-In pin of

IC1400(A)?

Is audio presenton LSOut-R/L

pins ofIC1400(A)?

Is audio enteringIC804 at pins 2,

5?

Replace Q800.

Replace IC6000.

Checkcomposite audio

line.

Does Q1201 testOK?

Is +9VSIFpresent on pin48, ICX2200?

Replace Q1201.

Check powersupply.

ReplaceICX2200.

Replace IC804.

ReplaceIC1400(A).

Check L/R audiolines.

5. No Audio

Yes

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

No

No

No

No

No

No

No

Section 2:CB Chassis

CB Chassis Safety Guidelines

X-RADIATION

To prevent possible exposure to radiation caused by excessive CRTAnode voltage, the CB Chassis incorporates a �High Voltage Shut-down� circuit. This circuit senses the level of flyback pulse from�Flyback Transformer� representative of the actual high voltage onthe CRT anode. When this level exceeds a predetermined voltage,the circuit shuts down the horizontal drive, preventing further gen-eration of anode voltage. In this condition, the horizontal drive is�latched� off. The drive will remain off until the microprocessor isreset.

SHUTDOWN CIRCUIT OPERATION

This shutdown circuit operates by means of sample HV taken frompin 6 of the sweep transformer TX3204. This sample of voltage isrectified, filtered and compared with a reference voltage(fixed byZDX3004 by the transistor QX3002. When the HV reaches the maxi-mum permitted voltage, the transistor QX3002 enters in conductionmode like consequence the transistor QX3001 also enters in conduc-tion. When QX3001 enters in conduction, the flyback pulses at theentrance of the video processor are 1 volt or less,the the TV goes outand enters in shutdown mode.

When the shutdown circuit is operating, the microcontroller willprevent the TV from being turned on again unless the microcontrollerhas been restarted by disconnecting the TV from the AC line.

CRT ANODE HIGH VOLTAGE MEASUREMENT PROCEDURE

Each CRT screen size has its own safe operating Anode Voltage andshutdown voltage. Critical Safety components (designated with an�X� in the component designator) are designed to operate the CRT ata safe operating Anode voltage and provide proper shutdown thresh-olds . If replacement of any of these components are deemed neces-sary, it is important to use original type Zenith replacement compo-nents. After replacement is made, confirm proper Anode voltageusing the following procedure.NOTE: The CB chassis does not have a bleeder resistor to discharge

the Anode voltage. High voltage can remain on the CRTAnode long after power is turned off. Before removing theCRT anode connection, turn off and unplug the television,then discharge the CRT Anode to DAG ground.

Measurement of the CRT Anode voltage must be performed using ahigh impedance high voltage meter, with no visible raster on thescreen, and operating at nominal horizontal scanning frequency.Connect a strong broadcast signal (or TV signal generator operatingat 15.734kHz horizontal scanning rate) to the RF input.

After discharging the CRT, connect a high impedance high voltagemeter to the CRT anode. Turn the television �on� and confirm a goodsignal is being displayed . Reduce Brightness and Contrast settingsuntil the picture is well extinguished.

Observe the Anode voltage meter reading and compare with thetable below for the proper CRT screen size. If the voltage reading ishigher that the maximum, verify circuit component values and properoperation.

7'6))2 &��:(' ,:�231 ,:�1%<7->) ���&)%1� /: /:

�� ������������ �� ���� ������������ �� ��

�� ������������ �� ������ ������������ �� ����

'31432)28�0):)0�6)4%-6

13(90)�0):)0�6)4%-6�320=

SAFETY CIRCUIT TEST PROCEDURE

This shutdown circuit operates by means of a sample of HV takenfrom pin 6 of the sweep transformer TX3204. This sample of voltageis rectified, filtered and compared with a reference voltage ( fixed byZDX3004) by the transistor QX3002. When the HV reaches the maxi-mum permitted voltage, the transistor QX3002 enters in conductionmode; like consequence the transistor QX3001 also enters in con-duction.

When QX3001 enters in conduction, the flyback pulses at the en-trance of the video processor (pin 18) are attenuated. If thisatenuattion is so that the flyback pulses at the entrance of the videoprocessor are 1 volt or less, then the TV goes out and enters inshutdown mode.

When the shutdown circuit is operating, the microcontroller willavoid that the TV is turned on again unless the microcontroller hasbeen restarted by disconnecting the TV from the AC line.

Equipment required:

a) Video Generator.

b) HV DC meter (0 to 40 KV, high Z).

c) External variable power supply (0V to 200 VDC @ 5Amps mini-mum).

d) 1 Giga ohm, 5%, 2W film resistor.Note: The external power supply may require a diode for blocking

voltage from the chassis power supply to the external powersupply. The diode should be connected between the positiveoutput of the external power and B+ of the chassis. Thecathode should be facing the B+ of the chassis. Therecommended diode is Part No. 103-00339-04A (400 V ofVRRM @ 3 Amps of average rectified forward current).

SHUTDOWN SAFETY CIRCUIT

CB-i

RX32111

470 pfdCX3002

DX3002

5.6KRX3005

1.5KRX3003

PROVRX3006

PROVRX3004

QX3002

RX3002M33K

CX320347uf

RX3007M8.2K

ZDX3400

DX3001RX3001M

10K

CX3001M0.01

QX3001

+9VSW

0.1 / 25vC2241M

PROVR2223M

VID

EO P

RO

CES

SOR

D2205R2224M

8.2KR2222M

4.7K

PROVC2215M

PROVC2214M

IC2200

FROM SWEEP TRANSFORMER

FROM FLYBACKPULSE

HP / XRAYPOT

CB-1

Power Supply

Introduction

The CB chassis is a cold chassis designed to support 27�, 32�, and 36� receivers. Its power supplyfeatures a controlled turn-on MOSFET gate driver circuit, direct B+ regulation, thermal protection circuitry,over-current protection (OCP), over-voltage protection (OVP), over-load protection, provision for futureuniversal power input (85VAC � 265VAC), and software controlled degaussing.

As with many SMPS circuits, this one activates as soon as it is connected to AC line current via plugconnector 3R8. Depending on the screen size, the CB can draw anywhere from 125 to 140 watts from theline supply. AC operating tolerances range between 90 Vrms and 135 Vrms. Note that while most of thefunctional portion of the CB chassis is considered to have a cold ground, the rectifier and primary side of theswitch-mode power supply have a hot ground.

Switch-Mode Power Supply Primary Side

FX3401, a 4 amp/250 volt fast-blow fuse, protects the CB chassis from AC line surges. EX3401, thespark gap, also provides some protection for the set. Incoming AC passes the fuse and is filtered byLX3401, CX3401, and CX3402. The switch-mode power supply (SMPS) uses a fairly standard bridgerectifier arrangement to develop raw B+, the voltage that runs the SMPS and ultimately the entire televisionset. DX3400 is the packaged bridge used in 32� and 36� sets. The 27� sets use discrete diodes DX3401,3402, 3403, and 3404. Rectifier output (raw B+) will be somewhere between 127.3 and 190.9VDC.This VDC is smoothed by and can be measured across CX3407.

DX3402

DX3403

DX3401

DX3404RX3401

CX3406

C3403

CX3407

CX3404

CX3405

CX3402

B+ VDC

LX3401

CX3401EX3401

RX3400

CX3400

FX3401

3R8

To SM Regulator

DX3400

To DegaussingCircuit

<<Figure CB-1>>

ICX3412 is the switch-mode regulator IC used to develop the numerous individual power supplies off thesecondary side of TX3401, the chopper transformer. The same chopper is used in all three of the CB sizes.This transformer isolates the hot portion of the chassis from the cold portion. Raw B+ feeds into pin 18 ofthe chopper. The other end of this coil, pin 11, connects with pin 3 of ICX3412. Pin 3 is the drain of theinternal MOSFET that drives the chopper transformer, while pin 2 serves as the MOSFET source.

ICX3412 functions when the voltage on pin 4 reaches +16 volts DC. This voltage is developed onCX3410. As it starts, the regulator pulls nearly 20mA of current from CX3410, causing its voltage to

CB-2

CB CIRCUIT DESCRIPTIONSbriefly drop. However, as the regulator begins to operate, it drives the chopper, and power derived frompin 13 of the transformer is drawn through DX3407 to maintain the voltage on CX3410. Overload andover-voltage protection are both internal to the regulator IC, and sensed through pin 4. Should either ofthese conditions occur, and latch will deactivate the oscillator inside ICX3412, thus eliminating any powersupplied by the chopper.

ICX3412

TX3401B+VDC

RX3416

To Rectifier Ckt

LX3410

LX3417PROV

LX3402CX3412CX3409 CX3418

PROV

CX3408

CX3411

DX3406

DX3407

DX3408PROV

C3413PROV

RX3405

RX3403 RX3404

RX3415PROV

RX3406

RX3407

CX3410

1

23

4

ICX3403

SecondarySide, SMPS

To SecondaryFeedback Ckt.

16

13

11

18

12345

<<Figure CB-2>>

Pin 1 of the regulator IC allows feedback input for voltage regulation. Control voltage is supplied to this pinvia ICX3403, an opto-isolator that receives output information from the secondary side of the chopper,particularly from the regulated B+. This feedback is accomplished by the programmable reference device,ICX3406. The output from this IC is fed to the opto-isolator, which then communicates this signal back tothe switch mode regulator circuit. The output voltage error derived from ICX3403 puts a DC bias acrossRX3405 and a drain current ramp on RX3403. The net effect of both the output voltage error and drain

OCP/FB Comp

INH Comp

4

1

3

5 2

OCP/FB

GND

Vin

Source

Drain

DRV

221-00060-03ICX3412

DRV Bias

OVP

TSDBias

UVLO Latch

Oscillator

<<Figure CB-3>>

CB-3

Power Supplycurrent ramp is input into pin 1 of ICX3412. This signal is then used to determine how regulation shalloccur as described below. OCP is also sensed using this pin. To prevent a false over-current detection atstartup however, a constant current sink has been included in the regulator. This measure is necessary dueto a current spike that often occurs at startup due to primary capacitance discharge.

The switch-mode regulator makes use of the resonant frequency set up by the chopper transformer andCX3408. This resonant frequency as well as the internal oscillator determines the nature of the MOSFET�sswitching. Hence, the term quasi-resonant may be applied to this regulator. Regardless of the terminologyused, the IC regulates voltage based on the following simple rule: duty cycle on-time reduces as voltagerises, while duty cycle off-time reduces as load rises. In this manner, correct voltage is maintained at thechopper transformer. The regulator�s fundamental switching frequency is 20 kHz, but when the receiver isswitched on, the regulator will operate as high as 100 kHz.

Switch-Mode Power Supply Secondary Side

The secondary side of TX3401 makes use of four separate windings, each with its own half-wave rectifier,to develop the various voltages required by the television set. As a result there are four primary stand-byvoltages (VSB): B+ (typically +130 volts), +12VSB, +15VSB, and +22VSB. The +15 and +22VSB areeach protected by 3A/250V, slow-blow fuses, FX3402 and 3403. The B+ line has sufficient protectionfrom the switch mode regulator. RX3423 is a fusible resistor that protects the +12VSB line.

<<Figure CB-4>>

R

A

C

ICX3406

RX3423

TX3401

1

23

4

ICX3403

CX3432PROV

LX3403

C3419

D3410 B+

CX3420

CX3431

+15VSB

RX3409

RX3427

CX3414PROV

CX3417PROV

CX3416

CX3415

RX3428

LX3415 D3409

ICX3404PROV

RX3408

RX3421

B+

CX3427

+12VSB

L3406

C3425

OUTIN1

2

3

ICX3402

C3426

+5VGEM

L3412

+5VPiP

W3403

L3407

+5VSBM+5VTUNE

FX3402

FX3403

LX3405DX3418

C3423+22VSB

C3422C3435

D3419

PDD

LX3404 D3411

C3421

CX3424

L3414RX3417

CX3428 CX3430

+15VSB

OUTIN1

2

3

ICX3401

D3416C3429

Q3405

W3405

L3409

W3404

+9VIF

+9VSB

R3425M R3426

+9VSW

LX3416PROV

+9VSWF

CX3436

D3417

Q3402R3418M

Q3404

R3412M

+15VSB

L3408

+15VSW

C3433

OUTIN1

2

3

ICX3405

C3434

+12VSW

RX3413

R3410

R3411

L3410

L3411

B+ +33VSB

-14VDC

+14VDC

-14AUD

+14AUD1

2

3

4

B+

+15VSW

IQB32B44WIQB36B44WONLY

4W9

±14 Volts DCfrom Flyback

Power ControlPin 32, IC6000

9-21049-21059-2106ONLY

3

6

8

5

7

9

1

4

3

2

1AudGND

To PrimaryFeedback Ckt.

PrimarySide, SMPS

CB-4

CB CIRCUIT DESCRIPTIONSThe B+ provides power for deflection via the horizontal output transistor (HOT), QX3204, and for thetertiary voltages that come from the flyback transformer, TX3204. It also develops the +33VSB for thetuner through RX3413. The +12VSB is regulated down to +5VSB by ICX3402. This +5 volt sourcepowers the microprocessor and EEPROM (IC6000 and IC6001 respectively), the Gemstar® board, thePiP board, and the tuner. The +15VSB is used as is to power sweep correction, horizontal drive amplifica-tion, and the ABL circuitry. It is also regulated by ICX3401 for +9V and by ICX3405 for +12VSW. Bothof these voltages are used as various video and IF supplies. The +22VSB is used to power the audioamplifier.

Two other voltages should be named here, although they are developed from the sweep transformer,TX3204. Namely the + and � 14VDC pass through the secondary of the switch mode power supplysection. These become the +/- 14AUD volts that power the variable audio output amplifier when they passthe series resistor and inductor arrangement shown on the schematic.

Some of the above voltages are switched on when the television powers up, rather than when it is justplugged in. These include +9VSW, +9VIF (some models), +9VSWF, +15VSW, and +12VSW. Theseare switched upon receiving a power on DC level from pin 32 of the microprocessor, IC6000. Thisswitches Q3402, which in turn activates both Q3405 and Q3404.

Degaussing Control

Degaussing is software-controlled by a signal from IC6000. When the receiver is switched on, pin 33 emitsa 760 ms signal that closes the degaussing relay, KX3401, via Q3403. This allows a brief moment of ACcurrent to magnetize the degaussing coil before the thermistor, THX3415, limits the coil�s power.

<<Figure CB-5>>

KX3401

DX3405

Q3403

THX3415

+15VSB

R34192

1

FilteredAC Line

DegaussingControl, Pin 33,IC6000

3T8 -- ToDegaussingCoil

Part Location Part # NotesICX3401 F-52403 All ModelsICX3402 F-53046 All ModelsICX3403 162-00028-01 All ModelsICX3405 221-00167-05A All ModelsICX3406 221-00265-03A All ModelsICX3412 F-53857 All ModelsTX3401 095-04576 All Models

<<Table CB-1>>

CB-5

Microprocessor Control

Introduction

The CB chassis employs IC6000 as its microcontroller. All end user and servicer controls are accessedusing this IC. While most of its functions will be described in terms of how they are used by other devices inthe receiver, a number of facts concerning the microprocessor and its input devices will now be presented.

The microprocessor�s job is to communicate control instructions and feedback information to and fromvarious other processors and input devices in the set. These include the video, audio, PiP, Gemstar®, audio& video switch ICs, the tuners, the EEPROM, the keyboard and IR detector, and the reset IC. Some ofthese use a direct connection via either switch, variable pulse, or DC level for communication. Others relyon the I2C bus, also known as serial clock and data bus. IC6000 provides 2 sets of clock and data lines.The first set is pins 37 and 39, and the second is on pins 36 and 38.

Input Devices

The IR detector demodulates pulses from the 40 kHz modulated carrier and sends the pulses to pin 15 ofthe microprocessor. There a special algorithm interprets the pulses as the various commands they represent.The keyboard is only slightly more complicated in its operation external to IC6000. It works by varyingvoltage on only two input pins (7 and 8) using resistor networks. A/D converters inside the micro interpretthe different voltages. Because voltage detection is used rather than active keyboard scanning, keyboardradiation is not a problem, but maintaining a +5VSB to within ±4% is critical. Both keyboard and IRinformation enter the CB chassis through connector 2K6.

Microcontroller

VDD is provided to pin 27 of the microprocessor from the +5VSBF supply. While this voltage is relativelylow, IC6000 is fairly demanding in terms of current. This same voltage powers the keyboard and IRdetector. The +5VSBF is also used as analog VDD and enters the micro at pin 18.

IC6002 serves as a reset IC for the main microprocessor. Note that it comes in a transistor type package.It accurately resets the micro after a power failure is detected. Pin 30 is the reset signal input for IC6000.The micro enters reset state after detecting a low on pin 30 of 2µS or more.

When the micro receives a power on signal from either the keyboard or the remote, the degaussing controlpin 33 turns on the degaussing circuit for 760ms. At the same time a constant voltage level from pin 32turns on the switched voltages in the power supply.

Horizontal and vertical synchronization pulses are fed into pins 1 and 2. These provide the microprocessorthe current sweep location of the beam, which is necessary to correctly interrupt main video for varioustypes of on-screen display (OSD). Neither of these sync pulses come directly from the IC2200 where theyare first produced. Horizontal sync is actually fed back from the sweep transformer on the flyback pulseline. Vertical ramp signal coming from pin 5 of IC2200 feeds the base of Q6002. Sync is produced on thecollector and fed to the vertical amplifier and through R6006M to the V-Sync pin of the micro. OSD orCC (closed captions) are sent as processed RGB (red, green, & blue) from pins 50, 51, and 52. At thosetimes it is necessary to blank out part of the main video, a fast-blank (FB) pulse is sent to the video proces-

CB-6

CB CIRCUIT DESCRIPTIONSsor from pin 49 along with the processed RGB. An exception to this occurs when Gemstar® is displayed.Under that circumstance, the fast-blanking pulse without RGB is sent to the video processor via theGemstar® board.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

36

26 27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52HSYNC

VSYNC

AFC

N/C

SD2

SD

KEY1

KEY2

AFC2

Y/C1-SENSE

Y/C2-SENSE

Y/CF-SENSE

CRT-PROT

MUTE

IR DET

N/C

N/C

AVDD

HLF

RVCO

VHOLD

CVIN

CNVSS

XIN

XOUT

VSS

R

G

B

FB

PiP-BRIGHT

N/C

N/C

N/C

AUD-SWAP

N/C

GM-RESET

YUV/SWITCH

H/T

SCL1

SCL2

SDA1

SDA2

IDENT

N/C

DEG-CTL

POWER

N/C

RESET

OSC-OUT

OSC-IN

VDD

IC6000

C6012MC6013

L6001

+5VSBM +5VSBF

CRY6001

R6034M

C6010M C6011M

C6008MR6080

R6033MC6009

R6032M

C6007M

R6031MC6006

C6005M

R6030L6007

+5VSBF

C6037

C6044

1 2 3 4 5

L6004

R6015M

R6016M

R6027

C6003M

L6005

C6035PROV

C6036M

R6010

C6040MC6002M

C6059M

Q6001

C6001MR6003M

R6004

R6001M

R6002M

Q6002 Q6004

R6007M R6005M R6006M

C6026M

R6008M

+5VSBF

D6002

C6058M

R6009M

R6017M

R6014M

R6011M

+5VSB

C6004M

C6022M

C6034M

R6063

R6064

Composite Video

C6060M

R6051

+5VSBF

R6052M

C6061M

R6013

C6041M

C6042M

C6043M

R6069M

R6070M

D6003

R6012M

V-Sync

V-RampFlyback

SD2SDAFC-Main

AFC2

CRT-ProtectMuteY/C1-SenseY/C2-SenseY/C-Front-Sense

2K6EXTERNAL KEYBOARD

<<Figure CB-6>>

The CB chassis features a halftone function that dims video surrounding OSD. This halftone circuit isdescribed in the video section, but is controlled by a DC level from pin 40.

Closed captioning display is accomplished in the microprocessor by use of the composite video into pin 22.Here a data slicer extracts the caption information and outputs it to the RGB pins when captioning is re-quested by the user. Note that when OSD needs to be on the screen, such as after a channel change orduring a volume change, the OSD will have priority, and CC will mute until OSD turns off.

Pins 5 and 6 are signal detection pins. When the either of the chassis� two tuners detects a bona-fide signalto the video processor, it separates horizontal sync signal from the IF and sends it to this portion of themicroprocessor. It can then be used to determine if a certain channel is carrying a valid active broadcast.

Automatic frequency correction (AFC) is sent to the microprocessor via pin 3 and pin 9 (for the secondtuner IF). The DC level on either pin tells the microprocessor if it needs to communicate an adjustment to

CB-7

Microprocessor Controlthe corresponding tuner to allow for clearer channel reception. The ideal voltage level here should bebetween +2.25 and +2.5 volts.

<<Figure CB-7>>

IC6000 provides CRT-protection for the set through pin 13. Operation of this shutdown depends on a DClevel from the CRT protection circuit off the vertical amplifier circuit. Should the vertical IC2100 fail, theDC level will no longer be present. In this situation, the CRT-protection latch will shut the receiver downthree seconds after detecting the failure. This circuit will prevent the CRT from burning a horizontal phos-phor line in the center of the screen or, worse yet, cutting the yoke end of the tube off completely.

The remainder of the I/O pins on IC6000 are briefly described here. Where necessary, a more detaileddescription will be provided in the circuit descriptions to which they relate. Pins 10, 11, and 12 are used asS-Video (Y/C) detection for the two Y/C jacks on the back and the Y/C jack on the front (where avail-able). Pin 48 emits a varying DC level that changes the bias on Q2211, effecting the PiP brightness of theRGB input to IC2200. Audio swap is accomplished by pin 44, which varies a DC level to a transistor arrayin the IF section. This array allows the audio signal being heard by the user to be switched between theprimary and secondary IF. Pin 42 controls the Gemstar® module�s reset function. Pin 41, the YUV-SWvaries a DC level on pin 36 of IC2200 to make it switch main video between separated luma and chroma

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

36

26 27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52HSYNC

VSYNC

AFC

N/C

SD2

SD

KEY1

KEY2

AFC2

Y/C1-SENSE

Y/C2-SENSE

Y/CF-SENSE

CRT-PROT

MUTE

IR DET

N/C

N/C

AVDD

HLF

RVCO

VHOLD

CVIN

CNVSS

XIN

XOUT

VSS

R

G

B

FB

PiP-BRIGHT

N/C

N/C

N/C

AUD-SWAP

N/C

GM-RESET

YUV/SWITCH

H/T

SCL1

SCL2

SDA1

SDA2

IDENT

N/C

DEG-CTL

POWER

N/C

RESET

OSC-OUT

OSC-IN

VDD

IC6000

C6012MC6013

L6001

+5VSBM +5VSBF

C6017

R6037M

C6016 C6056M D6001

C6014MR6059M

CRY6002PROV

L6002

R6060MR6035MC6015M

C6018M C6045M C6046M

Deg-CtlPower-Ctl

C6024M

C6025M

C6033M

C6023M

R6081M

C6065MR6024MC6067M R6088M C6091M

Q6003 J6001MC6046M R6023M

C6063M

C6055M

1

2

3

R6062MPROV

R6061MPROV

D6004

PROV

R6071MPROVC6054M

C6038M

C6039M

R6040M

R6058M C6057M

R6068

C6068M C6052M C6062M C6053M

VCC

GND

OUT

IC6002

Power-Fail

YUV-SwitchGM-Reset

PiP-BrightnessAud-Swap

Halftone

FB-MicroB-MicroG-MicroR-Micro

FB-PiP

4Q9

IQB32B44WIQB36B44W

ONLY

CB-8

CB CIRCUIT DESCRIPTIONSsignals entering IC2200 at pins 4 and 2 respectively and component video entering at pins 37 through 39.Note here that component video cannot be used as PiP. Lastly, pin 14 of IC6000 switches a DC level toalter the mute state of the audio amplifier.

Memory

The EEPROM, IC6001, is a small but vital part of the CB receiver. This 512 byte memory chip is respon-sible for storing servicer adjustments, channel information, and user settings, even when power is removedfrom the set. This information is transferred on the clock and data lines from the micro into pins 5 and 6.The EEPROM is powered by the +5VSBF source at pin 8.

1

2

3

4 5

6

7

8

IC6001

R6049

R6050M

+5VSBF

L6003

C6020 C6021M

1

2

3

4

5

+5VSBF

R6072R6039M

C6019M

R6046M

R6045M

R6047M

R6048M

C6047MC6048MC6049MC6050M

IDENTDATA2DATA1CLOCK2CLOCK1

R6041R6042MR6043R6044M

CLOCK2DATA2

(IC6000)3536373839

Clock & Datafor IF, Videoand Audio

4G9

<<Figure CB-8>>

IC Location Part # NotesIC6000 221-01388 All ModelsIC6001 221-00745-05 All ModelsIC6002 221-01177A All Models

<<Table CB-2>>

CB-9

IF Receiver

Introduction

The CB chassis utilizes two tuners in order to provide PiP without requiring a second external source. Thisis with the provision that the receiver�s antenna input is receiving multi-channel input. For example, a cabledecoder box usually only provides a single channel input. Although the television possesses two tuners,each is receiving an identical single channel, so a second external source would have to be used here if theuser desires his PiP to be different from the main screen. On the other hand, a standard cable input or evena regular antenna provides multiple channels that each tuner can demodulate individually.

The IF (intermediate frequency) section can be broken up into a half for each tuner. Those part designa-tions numbered from 1200 through 1249 relate to the primary tuner, WT1200. Part designations from1250 to 1289 apply to the secondary tuner, WT1250.

Tuner

For the most part, each tuner is fairly identical to the other as it relates to the rest of the chassis. Eachcorresponds respectively to IF IC1200 and IC1250 (IFPs or IF processors), which are also identical. IF

1

2

3

4

5

6

7

8

9

10

11

12 13

14

15

16

17

18

19

20

21

22

23

24DET-OUT SIF-IN2

1ST-SIF-AGCFM-DET

IF-AGC2 SIF-OUT

RF-AGC-ADJ VIDEO-OUT2

IF-IN1 EQ-FILTER

GND

EQ-INIF-IN2

APC-FILTER

SIF-IN1 VIDEO-OUT1

VCC VCO2

RF-AGC-OUT VCO1

AFT1 AFT-OUT

AFT2 IF-AGC1

IC1200

R1218MC1208

TP1206

C1210MR1208M

R1207M

+9VSW

C1209

R1206

C1211M L1202VCO

R1211M

C1212M

R1212MC1213TP1207

L1203

U1201 R1209M

R1210M

C1214M

R1216M

Q1200

C1215M

U1202

R1219MPROV

R1226M R1225M

W1200PROV

+9VSW

R1214

R1213M

R1222M

R1217M

CR1200

L1204

C1214C1222M

R1288M

C1219M

C1220M

R1223M

R1224M

1

2

3

4 5

6

7

8

U1200

C1201M

C1205M+9VSW

C1203M

C1204

C1221MPROV

R1202

C1200M

R1203M

R1201M

L1200

C1290

C1202M

C1207ML1201AFC

C1206M

R1204

R1205M

+5VTune

+33VSW

TP1200

ZD1230C1230

C1231M

C1232 C1233M

J1201MC1234

PROV

C1235M

PROV

TP1201

C1236C1238M

PROV

C1237M

PROV

R1230M

R1231M

SDASCL

Q1290

Q1293

Q1291

Q1292

R1297M

Audio-Swap

R1298M

+9VSW

R1299PROV

C1294

PROV

R1291M

R1293M

R1292M

R1290M

Comp-Aud

R1294M

C1292Comp-Aud2

R1296M

C1293M

R1289M

R1295M

Q1241

Q1240

+5VSB

AFC-Main

C1240

R1240M

C1241M

R1242M

R1241M

C1242

R1246M

C1244M R1245M

C1243M

R1244M

R1243M

Luma-SD

SD-Main

+9VSB +9VFil

L2901

C2935 C2936M

TP1205

TP1202

AGCDelay

AntennaInput

To 2ndTuner

To MainTuner

Splitter

IF-VideoMain

Main Tuner

11

10

9

8

7

6

5

4

3

2

1

WT1200SCL Main-Tuner

<<Figure CB-9>>

CB-10

CB CIRCUIT DESCRIPTIONScomes from pin 11 of the tuner, is filtered, and is fed into pins 5 and 6 of the IFP. AGC (automatic gaincontrol) voltage is applied to tuner�s pin 1 from pin 10 of the IFP. The +33VSB tuning voltage is applied topin 9, while the +5VTune processing voltage is on pin 7. Clock and data lines from IC6000 communicatewith the tuner on pins 4 and 5. In some receivers, the secondary tuners use the +9VIF at pin 6.

IF Processing

Each IFP is powered by the +9VSW on pin 9. After IF is received at pins 5 and 6, sound IF is separatedfrom picture IF emitted from pin 17. It reenters the IFP through pin 24 and finally exits through pin 1 as acomposite audio signal. Composite audio from each IFP enters a switching transistor array with partdesignations 1290 through 1299. The audio-swap line from the microprocessor controls Q1292. Thistransistor switches the rest of the array between composite audio from either the primary or secondarytuner.

<<Figure CB-10>>

Two variable coils are available with each IF processor for adjusting AFC or VCO. Use caution whenadjusting these, and be certain to mark their initial position in case they need to be adjusted back to theirprevious setting. A potentiometer is also available off pin 4 of the IFP. This adjusts the AGC delay insidethe processor.

1

2

3

4

5

6

7

8

9

10

11

12 13

14

15

16

17

18

19

20

21

22

23

24DET-OUT SIF-IN2

1ST-SIF-AGCFM-DET

IF-AGC2 SIF-OUT

RF-AGC-ADJ VIDEO-OUT2

IF-IN1 EQ-FILTER

GND

EQ-INIF-IN2

APC-FILTER

SIF-IN1 VIDEO-OUT1

VCC VCO2

RF-AGC-OUT VCO1

AFT1 AFT-OUT

AFT2 IF-AGC1

IC1250

R1265MC1270

TP1255

C1271MR1266M

R1267M

+9VIF

C1285

R1268

C1272M L1254

VCO

R1272M

C1273M

R1271MC1274TP1254

L1255

U1252 R1270M

R1269M

C1277M

R1273M

Q1251

C1276M

U1253

R1286MPROV

+9VIF

R1278M

R1276M

R1256M

R1257M

CR1250

L1251

C1259

C1261M

C1260M

R1259M

R1258M

C1264M

C1265M+9VIF

C1267M

C1266

R1261

C1262M

R1260M

R1262M

L1252

C1263M

C1269ML1253

AFC

C1268M

R1263M

R1264M

+5VTune

+33VSB

TP1250

ZD1250C1256

C1255M

C1257 C1254M

J1250MC1258 C1253M

TP1251

C1250

C1288M

PROV

C1287M

PROV

R1251M

R1250M

SDA2SCL2

Q1252

Q1253

+5VSBF

IF2-Video

AFC2

C1278

R1279M

C1279M

R1281M

R1280M

C1280

R1284M

C1282M R1285M

C1281M

R1283M

R1282M

1

2

4

5

3

U1251

L1250

PROV

+9VIF

Comp-Aud-2

SD2

TP1253

TP1252

2nd-IF-Tuner

11

10

9

8

7

6

5

4

3

2

1

WT1250

AGCDelay

CB-11

IF ReceiverThe remaining outputs of the IF processor are the AFC control to IC6000 from pin 14 and the IF videosignal which passes through the AV-switch (IC2900) as it travels to the comb filter. AFC output voltagecauses the microprocessor to determine any frequency corrections the tuner needs to make for a bettersignal. A portion of the luma from the IF-video is separated and filtered for the purposes of signal detectionat pins 5 and 6 of IC6000. From the main video signal, this separation occurs after the comb filter stage,where composite video exits IC2900 at pin 34. Signal detect information (SD) is then separated from theluma by transistors Q1240 and 1241 and their surrounding circuitry. For the second video signal, luma istaken immediately from the IF video signal out of IC1250 and separated by the circuitry including Q1252and 1253.

Part Location Part # NotesIC1200 221-00792 All ModelsWT1200 175-02770 All ModelsIC1250 221-00792-01 All ModelsWT1250 175-02770 All Models

<<Table CB-3>>

CB-12

CB CIRCUIT DESCRIPTIONS

Jack-Pack

The CB chassis provides multiple means for connecting external sources that supply video and audio signal.These provisions include two composite video (CV) inputs, two S-Video (Y/C) inputs, component video(YUV) input, corresponding left and right channel audio inputs for each video input, and, in some models, afront input jack featuring CV, Y/C, and stereo audio inputs. Additionally, a two-channel variable audiooutput is provided. This portion is discussed further in the audio circuit description.

Audio/Video Switch IC

In order to handle the multitude of incoming signals from the jack-pack, as well as the two internal IFsignals, the CB chassis employs an analog audio/video IC2900. This IC is powered at pin 18 by the+9VSW. While switching is analog, IC2900 is digitally controlled through the I2C (serial clock and data)bus connection at pins 26 and 27. This data stream communicates both user selections for signal input aswell as microprocessor priority commands. These priority directives may be explained by the followingexample.

<<Figure CB-11>>

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

36

26

27 28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54LINE2

VINE2

RINE2

LINE1

VINE1

RINE1

LINE4

VINE4

RINE4

VINE3

LINE3

RINE3

VINS1

LINS1

YINS1

RINS1

CINS1

GND1 ROUT1

YOUT1

LOUT1

VOUT1

YIN1

CLAMP1

VINS2

LINS2

YINS2

RINS2

CINS2

VCC CLAMP2

YIN2

ROUTD

LOUTD

CIN1

COUT1

VINS3

LINS3

YINS3

CINS3

RINS3

GND2

MUTE CIN2

O3

COUT2

ROUT2

YOUT2

LOUT2

VOUT2

SDA

SCL

I/O2

I/O1

IC2900C2934M

C2930M

C2929M C2931M

C2928MR2944M

C2933

C2932R2960M

R2958M

C2927

C2926

C2925

R2945M

R2940

C2924M

C2938M

R2943M R2933M C2923M

Q2902

R2934M

R2935M R2936M

+9VSW

Q2904

R2956MJumper R2957M

R2955M

R2937M

R2954M

Q2901

R2938M R2939M

+9VSW +9VSWF

Q2903

R2952M R2953M

IF2-Video

CV-Micro

IF-Video-MainY+C/CV-PiP

Luma-MainLuma-SD

Left-SWRight-SWY-Comb

CV-Comb

C-Comb

Chroma-Main

1 2 3 4 5 6 7 8 9R2931M

R2932M

ZD2903

R2930 Y/C-Front-SenseC2922M

C2921M

C2913 R2924

C2919MPROV

C2914R2925

R2973MC2917MPROV

C2920M R2928

C2916R2926

R2974MZD2908

R2927

Jumper

C2918MPROV

C2915R2923

ZD2903

C2901R2902 Jumper

ZD2904

R2901

C2902 R2904

R2969M

C2905M

C2903 R2906

R2970M

Y/C1-Sense

SDASCL

R2907

ZD2901

Y/C2-Sense

C2907R2909Jumper

C2908M

R2911

R2910

R2908

ZD2906

+9VSW

C2912

C2937R2914 Jumper

ZD2905

R2916

C2906 C2910R2921 Jumper

R2918C2909

C2911MR2922

R2919

R2912

R2971M

R2972M

ZD2910

R2920M

See Component VideoJackPack Section

11

23

18

6

5

4

10

2

19

9

8

3

7

17

12

7

24

12

24

17

Y/C1-In

Aux1-R-In

Aux1-L-In

Video1-In

Y/C2-In

Aux2-R-In

Aux2-L-In

Video2-In

4A8

IQB27B42WIQB27B44WIQB36B44W

ONLY

CB-13

A/V Switching

Suppose the user has composite video connected to the Video 1 input and S-Video connected to the S-Video 1 input. If the user selects video source 1 in the customer menu, the receiver must choose betweenthe CV and the Y/C signal. Each Y/C input has a sensor line that feeds the micro. If the micro detects thepresence of Y/C on video 1, IC6000 will direct the A/V switch to use that Y/C signal instead of the CV.Thus if it is present, Y/C has priority over CV.

IC2900 features three functional input arrays for jack-pack signal. Each array consists of left and right (L/R) channel audio input, CV input, and Y/C input. Additionally, the A/V switching IC provides another inputfor the dual IF-video signals and input for the Y (luma) portion of the component video input as well as itsassociated audio. CV, Y, and IF inputs should scope near 1.0Vp-p. Color burst from the Y/C inputs aswell as audio inputs should scope about 300 mVp-p.

For outputs, IC2900 uses pins 39 and 41 for L/R channel external audio. This is fed to IC1400, the audioprocessor and is used if the user selects a jackpack source. Pin 41 serves as the PiP video output. PiPvideo is sent as a composite video signal. However, if the PiP source is S-Video, IC2900 internally com-bines the Y and C signals into a CV signal. PiP CV should have a strength of 2.0 Vp-p at pin 41. Mainvideo is output to the video processor on pins 32 and 34 as chroma (C) and luma (Y), respectively. Theluma signal should be 2.0 Vp-p while chroma is about 600 mVp-p.

Composite or IF video input to the IC cannot be passed to IC2200 as composite video. Rather, the A/Vswitch passes CV or IF video via pin 41 through the comb filter section, where it is separated into luma andchroma and returned to pins 38 and 30 of IC2900. Voltage at pin 41 should be 2.0 Vp-p. The separatedsignal is then sent to IC2200 as Y and C along the main video lines. It should be mentioned that pin 34 alsosends the luma signal to IC6000 so that closed captioning (CC) and synchrony information can be extractedfrom it.

Part Location Part # NotesDL2400 223-00045 IQB27B42WIC2400 221-01040 IQB27B44WIC2900 221-01053 All Models

<<Table CB-4>>

CB-14

CB CIRCUIT DESCRIPTIONSComponent Video

Component video is handled differently than the other jackpack inputs. The CB lacks conversion circuitryto make component (YUV) signal into CV. For this reason, component video cannot be used for PiP,which requires CV input, and is furthermore not separated (or combined) into luma and chroma throughIC2900. YUV is directly input to IC2200 at pins 37 through 39. This arrangement necessitates the use ofa YUV switch from the microprocessor to the video IC. With respect to the A/V switch, however, the Ycomponent is still input to pin 2 and, when in use, is output as composite video to the microprocessor. Asmentioned before, this information is used to obtain CC and video synchrony. Moreover, the U componentmust be amplified to an acceptable level to be used by IC2200. Q2906 and 2907 serve this purpose usingthe +9VSWF for power.

C2904

C2940 R2905

C2939 R2903

R2976MR2975M

123

R2946

R2948R2950

Jumper

R2949

R2951

R2947

ZD2907

1 2 3 4

1 2 3 4

C2941 Q2906

R2961M

R2964M

R2964M

R2963MC2942

R2965M

+9VSWF

Q2907 C2943

R2966M

R2967M

R2968M

CR-InYUV-InCB-In

Pins 1-3IC2900A/V Switch

4C2

2C4

151413

24

17 212016

YUV-In Cr-In Cb-In R-In L-In

<<Figure CB-12>>

Comb Filtering

CB receivers use either a 1H glass comb filter, DL2400, or a 2H digital comb filter, IC2400. Both separatecomposite video into luma and chroma more efficiently than simple chroma traps and band-pass filters. Thisallows for video that is relatively free of color and luma distortion in high detail video objects. Comb filtersare better equipped to distinguish color from high-frequency luma, and can thereby reduce the crosstalkbetween the two.

For sets using DL2400, CV from IC2900 enters pin 2. Chroma is output to pin 3 while luma exits the filterat pin 5. Receivers that possess DL2400 still utilize a color trap (R2470M, L2411, and C2471M) and aband-pass filter (R2463, L2410, and C2442M) to ensure purity of both chroma and luma before it isreturned to the A/V switch.

CB-15

A/V SwitchingOn sets using the digital comb filter, CV is fed into an A/D converter at pin 5 of IC2400. This IC is pow-ered by the +5VTune at pins 3, 12, 20, and 27. Output for chroma is at pin 23 and for luma is at pin 25.Both are further cleaned by transistor circuitry that is powered by the +12VSW. Finally, �combed� lumaand chroma are returned to the A/V switch.

<<Figure CB-13>>

1

2

3

4

5

6

7

9

8

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15KILLER

VSS2

VDD2

CKIN

FILT

CBPF

VENH0

VENH1

1LINE

CORING

1/2VDD VDD3

VSS3TEST1

CLAMPC BIAS3

COUTBIAS1

A/DIN BIAS2

YOUTVREFH

VDD1 VREF1

VDD4VSS1

VREFL VSS4

IC2400C2409M

C2412M

C2414M

C2415MR2405M

C2417M

C2418MR2408M

C2413

R2409M C2419M

R2407M C2446M

R2406M

+5VTune

L2413

C2445

C2444MC2443

L2412

+5VTune

L2415

R2448M R2449M

C2449M

C2448

R2404M

Q2401

+12VSW

R2403M

R2402M

C2407M

L2402

C2405M

R2401M

C2406M

R2400M

C2451MPROV

FSCCV-Comb

C2423M

C2424M

R2446MC2447M C2455

+5VTune

R2454M

C2459

R2461M

R2460M

+12VSW1

2

3

4

5

DL2400

C2461M

C2450

R2471M

R2470M

L2411

C2471M

Q2413

Q2414

Q2411

+12VSW

2 3

46

L2409

23 4

6

L2408

Q2404

R2447M

R2436M

R2445M

R2444M

R2457M

R2439M

R2440M

C2439M

R2441M

R2463

C2442ML2410

C-Comb

Y-Comb

+12VSW

R2455M

R2426M

R2427M

Q2405

R2416M

R2417M

R2458M

C2452

R2472M

Q2406

+12VSW

R2473M

R2474M

R2430M

C2453

**See Note!

IQB27B42WIQB32B42WIQB32B84RIQB32B86RIQB36B42WIQB36B86R

**Note!Boxed AreasONLY for these:

CB-16

CB CIRCUIT DESCRIPTIONSIntroduction

The CB chassis video features include two-tuner PiP, comb-filtered video, auto kine bias, half-tone video,and direct component video input to the video processor. Certain receiver models also include 2H digitalcomb filtering, Gemstar�s® Guide Plus, front A/V inputs, and scan velocity modulation.

At the heart of the video circuitry is the NTSC video processor, IC2200. This video IC is powered by the+9VSWF at pins 33 and 44. Its primary means of communication with the microprocessor is via the serialclock and data (I2C) bus at pins 34 and 35.

Video Development

The NTSC video IC handles multiple types of video input and processes the output as RGB (red, green,and blue). Specifically, IC2200 receives luma and chroma (Y/C) information on pins 4 and 2 respectively.This input generally serves as main screen video. However, the video processor�s main video input can beswitched via pin 36 to use component video (YUV) that is input to pins 37 through 39. Secondary video(PiP) is input to the video processor as RGB through pins 26, 27, and 28. The PiP daughter board receivesvertical and horizontal sync information and thereby sends fast-blanking (FB) pulses to pin 25 of IC2200when main video needs to be blanked for PiP. In this sense, PiP has priority over main video. The micro-processor and, where used, the Gemstar® board also send OSD input as RGB to the video processor intopins 29 through 31 with FB signals from either source entering the video IC at pin 28.

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

TP5VBK

R6090PROV R6090M

+5VGEM +5VSBM

C6090

R6091M

Q6090

Q6091

R6092M

R6093M

R6094M

PDD

+5VPiP +9VSWF

+5VGEM

W6001

W6002W6003 W6004

C2290PROV

L2205PROV

R2297MPROV R2296M R2295M R2294M

R2290

R2291M

R2292M

R2293M

SCLSDA

VRamp

Y+C/CV-PiP

R-PiPG-PiPB-PiP

FB-PiP

FB-MicroB-MicroG-MicroR-Micro

B-OSD+GEMG-OSD+GEMR-OSD+GEMFB-OSD+GEM

Power-FailFlybackV-SyncIF2-VideoResetSCL2SDA2IRBLST2IRBLST1

Jumpers Used inNon-GemStar

Module ReceiversOnly

IQB27B44WIQB32B44WIQB36B44W

ONLY

GemStar Connectors& PDD Circuitry

PiPB1

PiPA1

GEM2

GEM1

<<Figure CB-14>>

Before video can be completely processed, it must also receive ABL (automatic brightness limiter) and ACL(automatic contrast limiter) information. IC2200 receives this at pin 3. Unlike many receivers, the CB usesa single input to control both ABL and ACL. For simplicity, pin 3 may be referred to as the ABL pin. ABLis first taken from pin 8 of the flyback transformer, TX3204. The signal is made positive across C2206 bythe voltage divider formed by R2201, R2212, and R2213. If current level in the picture tube penetrates the

CB-17

Video Processinglimiter threshold (1.5 mA for 27�, otherwise 1.6 mA), the corresponding voltage across C2204 triggers thelimiter circuitry internal to IC2200, thus reducing output level (and therefore the contrast and brightness) ofthe RGB signal. ABL helps to prevent blooming in the sweep that would otherwise occur as high currentdraw lowers the sweep voltage. It also serves to extend the life of the picture tube.

<<Figure CB-15>>

Another factor involved in determining the RGB outputs is the AKB (automatic kine bias) circuit whichfeeds into IC2200�s pin 21. This signal is derived from the CRT circuitry. It uses feedback informationdeveloped by three scan lines of video, one per color, in the over-scanned area above the video image. TheDC level returned is compared with an internal reference voltage that is determined in the service menusettings for optimum black levels. RGB color is adjusted accordingly and finally output on pins 22 through24 of the video IC.

IC Location Part # NotesIC2200 221-01394 All Models

<<Table CB-5>>

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24 25

36

26

27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48APED

C1IN

ABLIN

CVBS1/YIN

VTIM

MONOUT

NC

XTAL

FSCOUT

APCFIL

VCC2

TV/C2IN

COMB-CIN

YCLAMP

COMB-YIN

GND1

EW

REF EYIN

ER-YIN

EB-YIN

GND2

CVBS2/Y2IN

ABLFIL

VDP

VDN

VMOUT

REG

SCP

HP/XRAYPROT

YUV-SW

SDA

SCL

VCC1

R2IN

G2IN

HD-OUT

AFCFIL

IKIN

ROUT

GOUT

BOUT YS1

B1IN

G1IN

R1IN

YS2/YM

B2IN

IC2200

R2252M

C2231M

C2232M

C2230

C2234

C2233M

C2235M

C2236M C2237

L2202C2239

C2238M

R2253M

CRY2201

C2240M

R2256

R2254MR2255M

Q2208

+9VSWF

R2282

PROV

R2281PROV

C2240C2241

L2201

+9VSWF

R2251

R2250

C2228MPROV

C2229MPROV

C2225M

C2224M

C2223M

R2271M

R2242

D2211 D2212 D2213

C2222M

C2220M

C2219M

R2261M PROV

R2262M

PROVR2263M

PROV

R2266MPROV

R2265MPROV

R2264MPROV

C2245R2280M

+9VSWF

R2287

PROVQ2211

R2279M

R2278M

C2208M

C2209M

C2210M

R2206M

C2201

C2248M

C2247M

L2204

R2286M

PROV

R2285

R2283 C2249M

L2203

R2284M

C2250

C2204

+15VSW

B+

R2204M

R2213R2202C2206

R2216PROV R2212

R2201

Q2210PROV

R2205PROV

R2267MPROV

R2269MPROV

R2268M PROV

C2244

PROV

R2203M

C2216M

C2217

ABL

Luma-MainChroma-Main

FSC

CB-InCR-In

YUV-InYUV-Switch

SDASCL

R-OSD+GEMG-OSD+GEMB-OSD+GEM

PiP-Brightness

FB-OSD+GEM

FB-PiPB-PiPG-PiP

R-PiP

Pins 21-24Refer to RGBOutput Ckt

IQB32B44WIQB36B44WIQB27B44W

ONLY

IQB27B42W IQB32B86RIQB32B42W IQB36B42WIQB32B84R IQB36B86R

ONLY

HandInsertedComponent

CB-18

CB CIRCUIT DESCRIPTIONS

Before this processed video is pre-driven by transistors Q2205, 2206, and 2207, the video signal can bedimmed by the half-tone circuit. This circuit draws a limited amount of current when Q2209 is switched onby the half-tone pin 40 of IC6000. The half-tone circuit generates a rectangular area surrounding OSD inwhich video is present but shaded.

1 2 3 4 5 6 7

+12VSW

+9VSW

R2233

R2236

D2214

C2251Q2205

Q2206

Q2207

R2237M

R2234M

R2240M

R2257M

R2258M

R2259M

D2206 D2207 D2208

R2260

Q2209

C2243MPROV

Halftone

VID B+

Q2201PROV

D2204PROV

R2241M

PROV

ZD2201

R2231M

Q2202

J2201MPROV

R2245M

R2247M

R2244M

R2245M

R2243M

1: +12VSW2: Setup3: AKB-Sense4: GND5: R-Out6: G-Out7: B-Out

2C5 Key

IKINPin 21

B-OutPin 24

G-OutPin 23

R-OutPin 22

2C5

<<Figure CB-16>>

Video Amplification

After the RGB signal is pre-driven, it is sent to the CRT socket via connector 2C5. This socket boarddelivers the filament, focus and G2, and RGB video signals to the picture tube. Besides the AKB circuit, theCRT socket has an afterglow suppression circuit.

Each color is amplified in its own circuit section on the CRT board. The red amplifier section consists ofthose parts designated with 5120 through 5130. Green uses part designations 5140 through 5150 and blueuses 5160 through 5170. The video signal is cascode-amplified by a dual transistor arrangement for eachcolor. +235 volts from pin 1 of the 5F2 connector supplies power to the cascode amplifiers.

For example, Q5141 and 5142 amplify green signal. Frequency response is the major concern with regardto Q5142. By itself, Q5142 would tend to lose gain at higher frequencies. To remedy this problem,C5141M is added to the series-parallel network on Q5142�s emitter. This capacitor along with R5144Mprovide an improved response to higher frequency signals, while the resistor, R5143M, improves lowerfrequency response in the cascode amplifier. The resistor network formed here by R5145M and R5143Maffect the black level of the green. Q5141 also helps bandwidth of the cascode amplifier. It reducesfeedback caused by parasitic capacitance in Q5142. Q5141 has a very low feedback capacitance, lessthan 3pF, and a nearly 300V collector to emitter breakdown voltage. Its cut-off frequency is about 70MHz. Its collector passes green signal on to the push-pull coupling amplifier formed by Q5143 and Q5144and finally to the cathode through CRT1, the actual socket on the picture tube. This example applies to allthree color signals, with their respective components substituted.

CB-19

Video Processing

AKB signal is derived from the collectors of Q5124, 5144, and 5164. These are fed back to the AKBcircuit via pin 5 of the 5C2 connector and processed in the manner described above.

The CRT board also features a setup jumper for optimal G2 adjustment. The purpose for it is to force DCvoltage on the cathodes to be equal to the CRT cut-off voltage (170-190 volts DC with respect to G1).When jumped, the G2 setup circuitry grounds any incoming video signal. The servicer can then adjust theG2 pot, located on the flyback transformer, TX3204, until retrace lines just start to appear on the screen.Going back to the example of the green circuit, current then flows in Q5141, D5142, L5141, and RX5146.It is at this point that raster is almost cut off. When the jumper is released, the AKB circuit adjusts the colorwith the highest CRT cut-off voltage to the G2 setup voltage. The other two colors will be just slightly lowerdepending on their cut-off settings in the service menu.

1

12

11

109

8

7

65

4

CRT1

1

2

3

4

1 2 3 4 5 6 7

+235V

Q5121

Q5123

Q5101

Q5124

1

2

D5122

D5121

RX5129PROV

RX5128

R5173Jumper

L5121

RX5126

RX5127

L5122

RX5130

Q5122

R5122M

R5121M

Q5141

Q5143

Q5144

D5142

D5141

RX5149PROV

RX5148

R5172Jumper

L5141

RX5146

RX5147

L5142

RX5150

Q5142

R5142

C5143PROV

R5141M

Q5161

Q5163

Q5164

D5162

D5161

RX5169PROV

RX5168

R5171Jumper

L5161

RX5166

RX5167

L5162

RX5170

Q5162

R5162M

C5163PROV

R5161M

C5123PROV

+12VSW

R5165

R5164M

R5163M

C5161M

R5145M

R5144M

R5143M

C5141M

+12VSW

+12VSW

R5125M

R5124M

R5123M

C5121M +12VSW

C5105

R5107

C5104PROV

R5110PROV

+235V

C5100

W5101R5101PROV

R5106

C5103

G2W5102PROV

DAG1DAG2

C5106

D5101R5109

R5104

R5103

R5102

R5105

+235V

C5102PROV

C5101

L5101

C5164PROV

5C2 KEY

1: Blue2: Green3: Red4: GND5: AKB_Sense6: Setup7: 12VSWDGND

SETUP

BLUE

GREEN

RED

5F2

5C2

<<Figure CB-17>>

The afterglow suppression circuit is used to prevent any residue light that might otherwise remain on thescreen after shutdown. This circuit takes advantage of the fact that the filter capacitor on the +235V linetakes a relatively long period of time to discharge. The loss of filament voltage at shutdown triggers theswitching of Q5101, which then briefly interrupts the G1�s (pin 5) path to ground. The residue voltage on

CB-20

CB CIRCUIT DESCRIPTIONSC5101 causes the G1 to become more positive. Since G1 is otherwise considered ground for the CRT, thisaction reduces any remaining CRT potential, thus eliminating afterglow. C5101 controls the rise time of thiscircuit, while C5106 controls the dead-time on response.

Deflection Processing

IC2200 also supplies deflection signals to drive the sweep section. Vertical drive is supplied in the form ofpositive and negative ramp signals on pins 13 and 14 respectively. Simultaneously, a vertical ramp is alsosupplied from pin 5 of the video processor. This vertical signal is converted into vertical sync, directly bythe PiP board, and through transistors Q6002 and 6004, which then provide the v-sync to the microproces-sor and the Gemstar® board.

<<Figure CB-18>>

Horizontal drive comes from pin 19 of IC2200. This signal drives the horizontal output transistor (HOT).The flyback line taps off of the HOT collector to provide feedback to pin 18 of the video processor.Furthermore, this same flyback signal provides horizontal sync for the PiP, Gemstar®, and, through Q6001,the microprocessor. Pin 18 of IC2200 also serves the second purpose of protecting the set from highvoltage. While pin 18 normally receives horizontal feedback signal, a high voltage situation will activateQX3001. The collector of this transistor will then attenuate that signal. If attenuation lowers the signal to1.0 Vp-p or below, IC2200 will shutdown the CB receiver. Lastly, in terms of horizontal deflection, pin 11

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24 25

36

26

27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48APED

C1IN

ABLIN

CVBS1/YIN

VTIM

MONOUT

NC

XTAL

FSCOUT

APCFIL

VCC2

TV/C2IN

COMB-CIN

YCLAMP

COMB-YIN

GND1

EW

REF EYIN

ER-YIN

EB-YIN

GND2

CVBS2/Y2IN

ABLFIL

VDP

VDN

VMOUT

REG

SCP

HP/XRAYPROT

YUV-SW

SDA

SCL

VCC1

R2IN

G2IN

HD-OUT

AFCFIL

IKIN

ROUT

GOUT

BOUT YS1

B1IN

G1IN

R1IN

YS2/YM

B2IN

IC2200

C2240C2241

L2201

+9VSWF

R2214M

R2215M

C2213

Q2203

+9VSWF

C2212M

R2219M

R2220M

R2218

1

2

C2252MPROV

R2225M

+9VSWFR2226M

H-Drive

VDNVDPE/W

V-Ramp

Pin 18: Refer toHV Shutdown Ckt

PROVISIONAL ONIQB32B44WIQB36B44W

ONLY

4X9

CB-21

Video Processing

D2205

R2224M

R2222M

R2223MPROV

C2241M

C2214MPROV

C2215MPROV

ShutdownDC Levelfrom QX3001

FlybackPulse

To ShutdownPin 18, IC2200

<<Figure CB-19>>

supplies an E/W pincushion correction signal to IC3200, an op-amp in the deflection circuitry. This signal iscalculated by IC2200 to correct horizontal deflection that would otherwise give a �pincushion� appearancedue to the geometry of the CRT. IC3200 and its function is further described in the deflection circuitdescription. Note that it is only used in 32� and 36� CB receivers. Pincushion correction is wound into thedeflection yoke on the 27� receivers.

Two CB models, the IQB32B44W and the IQB36B44W, feature scan velocity modulation. Two coilslocated under the purity magnets on the CRT accomplish scan velocity modulation. These coils are con-trolled by the scan velocity modulator (SVM) board attached to the back of the CRT near the yoke. TheSVM receives fast-blanking and half-tone information from the microprocessor via the 4Q9 connector andvideo information from pin 15 of IC2200 via the 4X9 connector. These signals are processed to generate acurrent in the coils. The SVM varies this current to slow beam sweep at color transitions. The effectproduces a sharper video image in the CRT.

CB-22

CB CIRCUIT DESCRIPTIONS

Introduction

The CB chassis was developed to support CRTs ranging from 27� to 36�. Major component of the deflec-tion circuitry include IC2100, the vertical output IC; QX3203, the HOT (horizontal output transistor);TX3205, the horizontal drive transformer; and on 32� and 36� sets IC3200, the E/W pincushion correctionamplifier. Of course the yoke, connected at 3Y3, and the flyback (or sweep) transformer, TX3204, aremajor components as well.

Horizontal Drive

Horizontal drive (H-drive) enters the drive amplification circuitry through C3219 into the base of Q3201.This transistor and Q3202 amplify the h-drive using the +15VSW for power. H-drive then passes throughthe horizontal drive transformer for final wave shaping and voltage to current conversion. This modifiedhorizontal signal drives the HOT, QX3203. The HOT switches current flow in the primary winding of thesweep transformer, TX3204. Regulated B+ is applied at pin 3. Horizontal output also drives the horizontalscan signal in the yoke. Switching frequency of the HOT is 15.734 kHz.

1

3 4

5

6

TX3205

C3206

QX3203

LX3202

CX3212

C3204Q3202

C3203

R3205

R3204 CX3205

RX3207

+15VSW

R3203

C3202Q3201

C3201

R3202M

R3201M

C3219

CX3213PROV

DX3202

CX3257PROV D3203

RX3212

CX3258PROV

H-Drive fromPin 19, IC2200

Flyback Line

H-Output toFlyback & Yoke

<<Figure CB-20>>

Flyback Transformer

TX3204 uses HOT switching to generate high voltage. For this reason, the sweep transformer is oftenreferred to as the high-voltage (HV) transformer. HV should generally range between 29.4 and 31.2 kV.The flyback does not, however, exclusively develop high voltage. A number of secondary voltages arederived here as well. These should not be confused with the secondary voltages off the chopper, TX3401.The voltages developed off TX3204 are referred to as tertiary voltages in the power supply circuit descrip-tion.

Pin 2 of the sweep develops the +235V used to drive the cathodes at the CRT socket. This voltage isrectified and smoothed to DC by DX3201 and CX3208 and then applied to pin 4 of the 2F5 connector.Most of the secondary voltages are developed as DC in such a manner with the exception of pin 7�s fila-

CB-23

Deflection Controlment voltage, which is fed into pin 1 of the 2F5 connector, and pin 8�s ABL signal. For the filament�s part,since this voltage is needed only to heat the cathodes, it is not necessary that it be a DC voltage. ABL is fedto the video processor in order to regulate beam current.

CX3207PROV

RX3209

B+ DX3201

C3209

RX3208

+235V

CX3208

+14VDC

DX2104

C2112

C2111

RX2124

ABL

RX3217

RX3210PROV 1

2

3

4

+235 V

RX3211

CX3212

+35V

DX3252

CX3254 CX3253

CX3207A

RX3216

+33V

GND

G2

FOCUS

E

HV

TX3204 +14VSW

DX2105

C2114-14VDC

RX2125

-14VSW

RX3206

To FlybackLine Circuitry To HV Shut-

Down Circuit

To VideoOutput

2F5

6

9

7

5

8

3

2

1

H-Output

<<Figure CB-21>>

Pin 6 provides power for the +35V supply previously mentioned. RX3216 drops some of this voltage to+33VSW, which supplies the tuners. Pins 9 and 4 develop, correspondingly, a positive and negative14VDC. This ±14 volts powers the audio section. RX2125 and RX2124 serve as fusible resistors for the±14VSW supply to the vertical amplifier, IC2100.

Part Location Part # NotesIC2100 F-53864 All ModelsQX3203 F-53367 All ModelsTX3204 095-04438-04 All Models

<<Table CB-6>>

CB-24

CB CIRCUIT DESCRIPTIONSHigh Voltage Shutdown

The x-ray protection (high voltage shutdown) circuit uses the current from pin 6. DX3002 and CX3003convert this current to DC. The resulting voltage is applied to the resistor divider network in the emittercircuit of QX3002. Voltage applied to the base of this transistor remains constant because of the zenerdiode, ZDX3004. If HV reaches 35.7 kV (33.9 kV for 27� sets) DC applied to the emitter of QX3002will switch the transistor on. The resulting voltage across RX3002M will switch QX3001 on, attenuatingthe flyback signal on pin 18 of the video processor. If the signal is reduced to 1 Vp-p or less, IC2200 willcease production of H-drive and thereby shut down the set.

<<Figure CB-22>>

Vertical Amplification

The yoke receives vertical sweep drive from ICX2100, the vertical amplifier. This IC consists of a pump-up stage, a power amplifier, and thermal protection circuitry. The ±14VSW power the IC at pins 1 and 6.

DX3002

CX3002

CX3003

RX3005

RX3006

ZDX3004

RX3003

RX3004

RX3002M

DX3001RX3001M

RX3211

QX3002

RX3007

CX3001M

QX3001D2205

R2224M

R2222M

R2223MPROV

C2241M

C2214MPROV

C2215MPROV

From SweepTransformer

FlybackPulse

To ShutdownPin 18, IC2200

7

1

2

3

4

5

6

221-1410ICX2100

-

+AMP

Pump-Up

ThermalProtection

<<Figure CB-23>>

CB-25

Deflection ControlBoth positive and negative vertical ramp signals are required for operation. IC2200 supplies these to pins 4and 5 of the amp as non-inverting and inverting input. Pin 3 is an input for output stage VCC. Pin 7 is thepump-up output. Vertical output comes from pin 2 of the amp to pin 4 of the yoke connector. The otherend of the yoke provides feedback to pin 5 of the vertical amp and to the horizontal pincushion correctioncircuit.

<<Figure CB-24>>

The pump-up output from pin 7 feeds the CRT-protection circuitry. This circuitry provides a DC level topin 13 of IC6000, the microprocessor. The DC level at that pin should be between 3.6 and 5.1 volts. Ifthe voltage deviates from this range, the microprocessor will shutdown the set in 3 seconds. IC6000 willhave to be reset before the receiver can be turned on again. The purpose of this circuit is to prevent phos-phor burn or worse, the severing of the neck of the CRT. Pump-up current is rectified and smoothed byD2102 and C2108. R2109M and R2112M divide the resulting voltage before it passes through R2113Mto the micro. D2103 is a clamping diode.

D2102R2108M R2109M

C2108

D2103

R2112M

R2113M

+5VSBF

To Pin 13,IC6000

From Pin7, ICX2100

<<Figure CB-25>>

1

36

5

4

2

7 ICX2100

C2106R2101M

+14VSW-14VSW

C2103

CX2101

CX2102

D2101

R2102M

R2103M

CX2100 C2104

RX2105

CX2105

RX2106 RX2107 C2107

R2104M RX2110 RX2111 RX2114PROV

Vert-Output

Vert-Parabola

VDN, Pin14, IC2200

VDP, Pin13, IC2200

To CRTProtectionCircuit

32" & 36"ONLY

CB-26

CB CIRCUIT DESCRIPTIONSWidth and Geometry Correction

East/West pincushion correction is performed by circuitry built into 32� and 36� sets. The windings of theyokes used in the 27� CB chassis have this correction shaped into their design at assembly. Correction isnecessary on larger sets due to their geometry. As the CRT electron beam approaches the upper and lowerextremes of the screen, its horizontal scan lines sweep a wider length than they do in the middle of thescreen. DX3250, DX3251, CX3216, CX3252 and CX3256 act as a diode modulator circuit to limitcurrent in the horizontal yoke when the sweep is at the higher and lower edges of the screen. This diodemodulator relies on signals amplified by Q3250 and QX3251, and supplied by both the vertical yoke andthe video processor. Q3250 receives its power from the +35V derived at CX3253 off the flyback.IC3200 is an op-amp that boosts the signal from IC2200. It is powered by the +15VSW, and providesnot only pin-correction information, but also width control. Varying the DC level on the base of Q3250alters the overall screen width by changing the current through LX3201, the width coil.

R3252M

Q3250

R3255M

RX3256

R3253

QX3251

R3257M

TP3200

R3259

CX3251

LX3201

DX3250DX3251

CX3252CX3216

CX3256

C3217

H-Output from QX3203

LX3262

H Yoke

+35V

RX3215 CX3215

DX3203

RX3214 CX3218C3255

R3258

+15VSW

R3251M

W3259

W3202 LX3203

W3200

W3203

12345 6 7 8

IC3200

C3224

R3268R3267

E/W

R3266M

ABL

+15VSW

R3261M

R3262M

R3263M

R3264M

VerticalParabola

<<Figure CB-26>>

CB-27

Audio Development

Audio Processing

The CB chassis uses IC1400 to process audio. This IC features true MTS (Multi-channel TelevisionStereo) sound, dbx noise reduction, and SAP (second audio program) processing. Its I2C bus at pins 9 and10 allows adjustment for volume, balance, tone control, front surround sound, SAP switching, sourceselection, and stereo separation. IC1400 is powered by +9VSB at pin 24 and grounded at pins 22 and 11.

CB television receivers make use of at least 2 audio inputs to the audio processor. A third set of inputs isemployed on IQBxxB44W type models for audio boost purposes. A description of this process is below.The composite audio comes from a switch in the IF section through C1436 into pin 19. This allows selec-tion of composite audio from either the main or the PiP IF source. Refer to the IF circuit description for anexplanation of this switching. IC1400 processes this audio, separating SAP, left, and right audio. The leftand right channels are then output on pins 6 and 7. Alternately, the audio processor can use audio inputfrom an external source at pins 39 and 40.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

2425

36

26

27

28

29

30

31

32

33

34

35

37

38

39

40

41

42

43

44

45

46

47

48 BASSL2

TRE-R

TRE-L

SURRIN

SURROUT

LSOUT-R

LSOUT-L

NC

SDA

SCL

DGND

SAD

MAININ

MAINOUT

NC

PCINT1

PCINT2

PLINT

COMPIN

VGR

IREF

GND

SAPTC

VCC

BASSL1

BASSR2

BASSR1

SURRTC

TVOUT-L

TVOUT-R

AUX2-L

AUX2-R

AUX1-L

AUX1-R

VLTC

VLDC

VCAWGT

VCATC

VCAIN

VEOUT

VETC

VEWGT

VE

SAPIN

SAPOUT

NOISETC

STIN

SUBOUT

IC1400

C1401M

C1402M

C1404M

C1416

C1435MPROV

C1434MPROV

R1401 R1402

R1425M

C1421

C1420R1406M

C1418

C1436

C1413

R1404M

C1425

R1421M

R1422M

+9VSW

C1433MC1430

C1403M

C1406M

C1431M

C1409

C1410

R1409M

C1432

C1415

C1414

R1405M

C1417

C1427

C1426

C1428

C1419

C1422

C1424

R1407M

R1408M

* Not usedin all models

To AudioBoost Circuit *

SwitchedAudio In

CompositeAudio In FromIF Circuit

Clock &Data Lines

To Audio &External Amps

<<Figure CB-27>>

All audio input and output pins should meter 4.0 DC volts. Signal at pin 19 should have a strength of 245mVrms. All other audio inputs and outputs on IC1400 should scope at 490 mVrms. This includes the audioboost I/O described now.

CB-28

CB CIRCUIT DESCRIPTIONSAudio Boost

Those sets that have the audio boost feature output audio signal on pins 43 and 44 to IC1401. This IC ispowered by the ±14AUD. It strengthens the audio signal and returns it to pins 41 and 42 of the audioprocessor. From here, the boosted signal is output from IC1400 on pins 6 and 7.

OUT1 OUT4

-IN1 -IN4

+IN1 +IN4

V+ V-

+IN2 +IN3

-IN2 -IN3

OUT2 OUT3

10

9

87

6

14

13

12

11

5

4

3

2

1

IC1401

R1490M

R1491M

R1489M

C1484

R1488M

-14AUD

C1482M

R1486M

R1487M

C1479 C1478M

R1484M

R1485M

R1482M

R1483M

R1492M

C1483

C1477M

C1476M

R1477M

R1481M

R1478M

R1479M

R1480

C1475

R1475M

R1493M

R1476M

C1474MC1473

+14AUD

C1481C1480M

C1472M

R1474M

C1471M

R1472M

R1473M

R1471M

43

41

42

44TVOUT-RIC1400AUX2-R

AUX2-LIC1400TVOUT-L

<<Figure CB-28>>

Audio Amplification

CB receivers employ two 8-ohm, 7-Watt speakers. These are driven by IC804, the stereo audio amplifier.Although the audio amp is capable of driving 10-Watt speakers, the supply voltage has been reduced from+36 volts DC to +22 volts. Normal gain of this IC is 42 dB. In order to drive the speakers at 5 Watts, asignal strength of only 50 mVrms is necessary. Such a low strength signal is susceptible to noise interfer-ence, so the gain is reduced to 32 dB by negative feedback from the output in order to allow for an in-creased signal strength of 142 mVrms. R868 and R869 accomplish this reduction for the right channel andR858 and R859 do so for the left channel. The output level from the amplifier is 425 mVrms. Cut-offfrequency is 14.3 kHz and is determined for right and left channels by C865M and C855M respectively.

IC Location Part # NotesIC803 221-00170 All ModelsIC804 F-53765 All ModelsIC1400 221-01127 All ModelsIC1401 221-00188 IQB27B44W

<<Table CB-7>>

CB-29

Audio DevelopmentThe +22VSB is supplied to pin 10. Pins 4, 9, and 12 are grounds for the amp. Pins 5 and 2 input left andright (L/R) channel audio fed through C851 and C861, which eliminate any DC accompanying the signal.Pin 3 provides a reference voltage. L/R output comes from pins 7 and 11. Pin 8 is a line that, upon receiv-ing a switching DC level from the micro, mutes the speakers. This occurs when the user selects the speakercutoff option.

External Audio Output

External variable monitor output jacks are included on the CB jack-pack. Their signal is provided byIC803, a dual op-amp that receives L/R from IC1400 into pins 3 and 5. This amp IC is powered by the±14AUD at pins 8 and 4. Audio output to the variable audio output jacks comes from pins 1 and 7. Theop-amp provides a net gain of 12 dB.

1

2

5

64 9 12

113 10

8 7

OUTR OUTL

VCC

GND

VREF-INR

+INR

-INL

+INLMUTE

GND

GND

IC804

1

2

3

4C854

C864

C853

C863

R853

R863

C852

R859

R858

R870

C847PROV

Mute

C862

+22VSB

CX841C842

C843

R868

R869

R861M R851M

R862M R852M

6 7

C861

C851

C865M C855M

C822

C832

1

2

3

4 5

6

7

8

IC803

R826M R836M

+14AUD

-14AUD

C850 C844M

C857 C856M

R823M

R833M

R822M

C823

R832M

R824M

C833

R834M

R825

R835

L & R Outfrom Pins6 & 7, IC1400

9S4

27 2625

Part of J1,Jack Pack

VariableMonitorOut-Right

VariableMonitorOut-Left

To TVSpeakers

<<Figure CB-29>>

CB-30

CB TROUBLESHOOTINGStart

1. No Power

Plug receiverinto AC source.

ReplaceFX3401.

ReplaceFX3402.

Check RX3423.Replace TX3401 if

necessary.

Check DX3406,DX3407, CX3410.Replace ICX3412

if necessary

ReplaceICX3402.

Yes

No

No

No

No

No

No

No

Yes

YesYes

Yes

Yes

Yes

ReplaceIC6000.

Check +15VSBsupply at CX3428.Check ICX3401.

Check Q3402 &Q3405.

ReplaceIC2200.

Refer to shutdowntroubleshooting.

No

No

No

No

Yes

Yes

Yes

Yes

Is ACconnected?

Does FX3401conduct?

Is B+ present atCX3420?

Does FX3402conduct?

Is pin 3,ICX3412

switching?

Is +12VSBpresent across

CX3427?

Is +5VSBpresent across

C3426?

Does pin 32,IC6000 emit aDC pulse at

startup?

Is +9VSBpresent across

C3429?

Is +9VSWpresent across

CX3436?

Is Horz & Vertdrive present onpins 13, 14, 19,

IC2200?

Are ICX3406and ICX3403

OK?No

Yes

ReplaceICX3403,

ICX3406 asnecessary.

CB-31

Flowcharts2. Shutdown

Start

Does the setpower up formore than 2seconds?

Does the Vp-plevel at pin 18,IC2200 stay

below 1.0 volts?

Checkmicroprocessor

ciruitry.

No

YesCheck HV-

shutdown circuit,sweep

transformer.

Does the setshutdown afterjust 3 seconds?

Check IC2100 &CRT protection

circuit.

Yes

Yes

No

No

Is B+ running at aconstant DC

level?

ReplaceICX3412.

No

Yes

CB-32

CB TROUBLESHOOTING3. No Tuning Start

Are all tunervoltages

present? (Referto schematics.)

Check tunerpower supplies.

Is IF present atpin 11, WT1200?

Does changingthe tuner fix the

problem?

Check clock anddata lines.

Replace IC6000if clock & data

lines OK.

Is IF present atpins 5, 6,IC1200?

Check IF line.Replace U1200

if necessary.

Is IF present atpin 17, IC1200?

Check IC1200power supplies.Replace IC1200

if necessary.

Refer to No Audio and NoVideo Troubleshooting.

Yes

No

No

No No

No

Yes

Yes

YesThis procedure may beapplied to the 2nd tuner

section as well.

CB-33

Flowcharts

4. No Video Start

Is raster presenton the screen?

Is 1.07 kVp-psignal present on

collector ofHOT?

Is regulated B+present at pin 3

of TX3204?

Check powersupply.

Check TX3204for high voltage.

Check HOT andH-drive circuit.

Is there luma atpin 4, IC2200?

Is luma missingat pin 34,IC2900?

Is RGB outputpresent at pins

22 - 24, IC2200?Replace IC2200.

Is RGB presentat pins 1, 2, 3,

connector 5C2?

Check Q2205,2206, 2207.

Is the SETUPjumper open?

Is +235 VDCpresent across

C5100?Check TX3204.

Check G2adjustment.

Yes

No

Yes Yes

Yes

Yes

Yes

Yes

Yes

No No

No

No

No

No

No

Remove setupjumper.

Is compositevideo missing atpin 36, IC2900?

Check Q2901and +9VSW

source.

No

Yes

NoCheck DL2400or IC2400 and

comb-filtercircuitry.

Is there video IFpresent at pin50, IC2900?

Yes

Check video IFline, Q1200, pin

21, IC1200

No

Yes

Replace IC2900.

CB-34

CB TROUBLESHOOTING

Check audiopower supply.

Is +22VSBpresent on pin

10, IC804?

Start

Does DC levelchange at pin 14,

IC6000, whenspeaker cut-off is

toggled?

Is L/R channelaudio missing atpins 2, 5, IC804?

Is L/R channelaudio missing at

pins 6, 7,IC1400?

Is compositeaudio missing at

pin 19 ofIC1400?

Is compositeaudio present atpin 1, IC1200 (or

IC1250)?

Replace IC6000.

Replace IC804.

Check IC1400VCC. If it is

present, replaceIC1400.

Check L/Rchannel lines.

5. No Audio

Yes

No

Yes

Yes

Yes

Yes

Yes

No

No

No

No

No Replace IFprocessor.

Check Q1290,1291, 1292, &1293. Replaceas necessary.