MODEL ： VM-1201

REVISION ： A0

DATE ： MAY. 21. 2001

DOCUMENT NUMBER ：

SERVICE MANUAL

WARNING ==========

For continuous protection against radiation, shock and flame, replace only with same type and rating components specified in the approved sheets.

Disclaimer

Speco Technologies makes no representation or warranties, either expressed or implied, with respect to the contents hereof and specifically disclaims any warranties, merchantability or fitness for any particular purpose. Furthermore Speco Technologies reserves the right to revise this publication and to make changes from time to time in contents hereof without obligation to notify any person of such revision or changes.

Table of Contents

1. INTRODUCTION .......................................................….....…………………………………….. 3 1.1 OPERATIONAL SPECIFICATION ................................…............…………………….……... 3

1.1.1 Operating Environment ...........................................…..………………………………….. 3 1.1.2 Signal Input Requirements ...................................….....…………………….……………. 4 1.1.3 Power Input Requirements ................................…......……………………....…………… 4

1.2 FUNCTIONAL SPECIFICATION...........................…....……………………...............………. 5 1.2.1 Display Quality....................................................………………….………..………….. 5

1.3 CONTROL AND ADJUSTMENTS.........................…....................…………………………... 6 1.4 PHYSICAL SPECIFICATIONS................................….........……………………......………... 7 2.THEORY OF OPERATION..........................................…..…………………….........………….. 7 2.1 MAIN POWER SUPPLY BLOCK......................….....….……………………...............……... 7 2.2 VIDEO INPUT BLOCK ............……….......................…………………….............…………. 7

2.2.1 Video filter………….….…………………………………………………………………. 7 2.3 VERTICAL & HORIZONTAL PROCESSOR 7

2.3.1 Vertical guard……………………………………………………………………………… 7

2.3.2 Vertical Drive Output………..……………………………………………………………. 7

2.3.3 Sync Separator……………………………………………………………………………. 7

2.3.4 Phase Detector…………………………………………………………………………….. 7

2.3.5 Supply……………………………………………………………………………………... 8

2.3.6 Horizontal Oscillator, Horizontal O/P Transistor and Second Phase Detector…………… 8

2.3.7 Mute Output And 50/60 HZ Identification………………………………………………... 8

2.3.8 Sandcastle Output…………………………………………………………………………. 8 1

2.4 VERTICAL DEFLECTION BLOCK.........................................……………………..………... 8

2.5 HORIZONTAL DEFLECTION BLOCK.............................……………………............……... 8

3. TROUBLESHOOTING INSTRUCTIONS............................................……………...…….….. 9

3.1 NO DISPLAY, NO POWER.......................…………………………………………………….. 9

3.2 NO DISPLAY, (POWER OK)............………………………………………………………….. 9

3.3 NO DISPLAY, (NO ASTER) ……………………………………………..........…………….. 10

3.4 NO PICTURE OR NO COLOR (RASTERK)..................………………………...…………. 10

3.5 VERTICAL DEFLECTION FAILURE............................................…………………..……….. 10

APPENDIX：

A. SPARE PARTS LIST

B. SCHEMATICS AND PCB LAYOUT DIAGRAM

2

Audience

This service manual is primarily for system / service engineers, distributors and dealers. It carries the assumption that the reader understands the basic operating concepts.

Purpose

This manual contains reference data for Speco Technologies monitor. It gives information regarding the operating principles of monitors, as well as technical service and maintenance information.

1. Introduction

The VM-1201, high performance monochrome monitor, display over 1,000 TV lines resolution on a bright 12-inch picture tube. This combination provides excellent multi-screen displays commonly produced by picture-in picture and quad units. All user controls are conveniently located behind a protective front panel door. This monitor can be placed on a desk or mounted in a standard 12-inch rack (with an optional rack mount kit) This series are housed in an enameled steel cabinet for ruggedness and durability, and with the exception of the picture tube, the circuitry is all solid-state. It also feature video loop through connectors with switchable high-z/75ohm termination. The VM-1201 is an excellent choice when you require a rugged, compact B/W monitor. The exquisite and reliable design of this monitor will provide years of trouble-free operation.

1.1 Operational Specification

1.1.1 Operating Environment

‧ Temperature

Operating ：-10 to + 50℃

Storage ：-20 to +70 ℃

‧ Humidity (Relative)

Operating ：10 to 85% non-condensing

Storage ：10 to 95% non-condensing

3

1.1.2 Signal Input Requirements

‧ Connector

For CVBS：BNC terminal

Type：composite video input Level：1.0Vp-p

Synchronous：0.3 V

Luminance：0.7V

Polarity：Positive bright

Impedance：75 ohms

1.1.3 Power Input Requirements

‧ Operating Voltage Range：90 ~ 264 VAC at 50 / 60 ±3Hz

‧ Input Current at 90 VAC

Operating：0.5 Amps rms. maximum

‧ Input Current at 264 V

Operating：0.3 Amps rms. maximum

‧ Power consumption

Normal operation：30 Watts maximum

1.2 Functional Specification

The standard conditions for verifying the following specification are as below： 4

•

•

•

•

•

Temperature ：25 ±5℃

Magnetic field ：No additional magnetic field in near side

AC line Input ：100 ~ 240 VAC ±10%, 50/60 ±3Hz

Warm-up Time ：30 minutes min. after power on and signal applied

Ambient light ：400 to 600 lux.

1.2.1 Display Quality

‧ Display area (monoscope pattern)：full scan

‧ Video Amplifier Performance

‧ Video Bandwidth ：8 MHz

‧ Light output (brightness and contrast at maximum)

‧ At block pattern ：100 FL minimum

‧ At full white pattern ：50 FL minimum

‧ Contrast adjustment range：Over 12 dB

‧ Linearity (cross pattern)

‧ Horizontal ：10% maximum

‧ Vertical ：10% maximum

5

‧ Picture geometry：≦ 2.5%

‧ Picture centering：≦ 6mm

‧ Size stability：Picture luminance from 5 FL to max., the size shall be less than 2.5%

(with full white pattern)

‧ Swing and jitters：Swing and jitters are not allowed (viewed at 50cm from eyes to

screen).

‧ Focus：(viewed at 50cm from eye to screen, contrast adjusted to set luminance at 20 FL

with full white pattern, brightness set at raster just disappeared) Inspect full character pattern, all characters should be distinguished.

1.3 Controls and adjustments

•

•

•

•

•

•

•

•

External user’s controls：

Brightness adjustment

Contrast adjustment

Horizontal hold

Vertical hold

Volume adjustment (optional).

1.4 Physical Specifications

Dimension：313mm(H) ×310mm(W) x300mm(D)

Net Weight：9 Kg

2. Theory of Operation 6

This section describes each functional block of the monitor.

2.1 Main Power Supply Block

•

•

•

•

•

•

•

•

•

•

•

•

AC power input：AC socket

Line input noise / EMI filtering：Line filter T902 ;

X-Cap C901, C902.

Y-Cap C903, C904, C905.

Over current protection：Fuse

Power on/off control：Power switch

AC to DC conversion and filtering：Diode D901, Capacitor C906

Start-up circuit：R914, C914.

Main switching power controller, free run oscillation, voltage feed back, switching duty control,

cycle by cycle over current protection, power MOSFET driving：U901-UC3842

Free run oscillation：R909, C910.

Voltage feed back and control：output voltage control R910, R911 & VR901; gain compensation

C911& R903.

Current sensing and cycle by cycle over current protection：Current sensing R904; Noise

filtering R906, C909.

Energy storing and transferring：Power transformer T901.

Power driving：Power MOS transistor Q901. 7

•

•

•

•

•

•

Snubber circuit：Snubber C907, D902, R902.

Primary side self-powering circuit：D903,C914.

Output 13.5 volts for vertical & horizontal drive circuits：D904, C915.

Output 27.5volts for horizontal deflection circuit：D906 ,C916.

2.2 Video input block

Signal input buffering and switch

‧ CVBS Input buffer ：Q201 & R201,R202.

Video filter & output stage.

‧ Video input：Through C202 to W202 (Contrast VR ) and differential amplifier Q202,

Q203.

‧ Video amplifier: Cascade amplifier R219, Q204, Q205, R222, C206.

‧ Brightness control:VR201, R214, R225, R226, Q204.

2.3 Vertical & horizontal processor

2.3.1 Vertical guard: This vertical feedback signal on pin2 when the level on pin 2 is below 0.35v or high

than 1.85v the guide circuit inserts a continuous level of 2.5V in the sandcastle output

signal of pin 17.The results in the blanking of the picture displayed, thus preventing a

burnt-in horizontal line.

2.3.2 Vertical drive output:

The drive o/p pin1 of U401 delivers a drive current of 1.5mA at 5V output through R302

to U402 pin1.

2.3.3 Sync separator: The video input through C401, R401 and filter C402 to pin 5 of U401.The Sync separator

is designed such that the slicing level is independent of the amplitude of the Sync pulse. The

8

black level is stored at pin7 by C404. The slicing level is stored at pin6 by C403 and decided

by R403.

2.3.4 Phase detector: The phase detector circuit is connected to pin8. The circuits are activated depending on

the voltage of pin18 and the state of the Sync pulse noise detection circuit, C405, C406,

R405.

2.3.5 Supply (pin9, 10 and 16):

U401 can start operating by application of a very low supply current into pin16. When the

starting circuit is taken from pin10 via internal diode, and the voltage on pin16 will stabilize

to a typical value of 9.4V 2.3.6 Horizontal oscillator, horizontal output transistor, and second phase detector (pin11, 12,

14 and15): The oscillator is connected to pin15. An external RC; C409, R412, VR401; sets the frequency combination between pin15 and ground. The open collect horizontal output is

connected to pin11. The duty factor is set by an internal npn emitter follower stage

connected to pin14. When no flyback pulse is detected at pin12 the duty factor of the

horizontal output stage is set to 50%.

2.3.7 Mute output and 50/60HZ identification (pin13):

Pin13 has the possibility for 50/60HZ identification. A pull-high resistor R408 achieves

the function.

2.3.8 Sandcastle output (pin17): The sandcastle output pulse generated at pin17.

2.4 Vertical Deflection Block

• Power amplifier：

‧ The DC level across C308 and the current is detected by R306 and feedback to U401 through R311.

‧ The driver output comes from pin5 and it drives the yoke by a negatives slope current ramp R419 is used to stabilize the power amplifier.

‧ Boost power D301, C305 is connected to pin3. 9

•

•

•

•

Flyback generator：

‧ U301 pin6 is the output of the flyback generator that when driven, jumps from low to high condition C305 transfers the jump to pin3

Vertical size control：VR301, R312, R308.

2.5 Horizontal Deflection Block

Horizontal drive buffering：Driving source-U401 pin11. Driving transistor-Q40, to pull high the

driving waveform to drive the Q401(MOS FET).

Horizontal deflection：Horizontal Output transistor-Q401; Load-Yoke inductance and C414 ;

D401, High Voltage generation-flyback transformer .

3 Troubleshooting Instructions

‧ This chapter describes possible failures of the monitor with corresponding check/correction actions, and guidelines for safe operation and service of the monitor.

3.1 No Display, No Power

3.1.1 First of all, turn power off, use multimeter to check Q901, and R904, replace if bad. Turn power on after that.

3.1.2 Check DC voltage across C906. If no voltage or voltage too low, check and fix the following

components：AC receptacle poor contact, fuse F601 broken, power switch malfunction, or

bridge diode D901 bad

3.1.3 Check voltage on U901 pin 7 for start up condition：If voltage on U901 pin 7 reaches the start

up voltage(around 15 to 17.5V), U901 UC3842 will start to work and output 5V at pin 8. If

voltage on U601 pin 7 is too low, check and fix following circuits：start up circuit R914,

and C914.

3.1.4 If no output pulses at U901 pin 6, check and replace U901. 10

3.1.5 If driving pulses at U901 pin6 and drain of Q901 are correct but voltage at U901 pin 7 low than threshold voltage --causing U901 to stop and restart periodically, check and repair following circuits. Power transformer T901 bad; D903 short-circuit/opened.

3.2 No Display, power output normal.

3.2.1 Check and fix FBT B+：If no B+（27.5V）on pin2 of FBT replace D906, C916.

3.2.2 Check driving output voltage：0 or very low check and replace Q402, Q401.

3.2.3 Power off monitor. Check yoke connection. Use multimeter to check D501, D502, D401, Fix if any is bad.

3.2.4 Power on, check voltage at pin10 of U401 if no voltage, check and fix Vertical circuit B+, D904.

3.3 No Display (No Raster).

3.3.1 Check yoke connection.

3.3.2 Check CRT board and verify CRT heater is on.

3.3.3 Check G2 voltage if fail, check and fix FBT or D502.

3.3.4 Check K (cathode) voltage at negative of D501 about 150V, If no voltage output Check and replace D501 and C501.

3.4 Vertical Deflection Failure

3.4.1 Vertical display can't be held--check and fix：U401.

3.4.2 Vertical raster abnormal (one horizontal line, size too small or fold back on top / bottom) --

check and fix：14V supply at U402 pin2, if has voltage check and fix U301.

11

Appendix A. Spare Parts List

Location Parts Number Description F901 28-1100-0006 Fuse, 2A/250V, slow blow D901 06-3100-0005 Diode 3A, 600V, RS407 D902 06-1100-0001 Diode, 1.5A, 800V, BA159 D501, D502 06-1100-0023 Diode, 3A, 800V, FR107 D903, D904, D301 06-1100-0014 Diode, FR1005 D906, D401 06-1100-0058 Diode, 2A, 600V, FR205 Q901 08-3100-0011 Power MOS 2SK2996 Q201, Q202, Q206, Q402, Q501 08-1100-0003 Transistor NPN 2SC1815 Q205 08-1100-0001 Transistor NPN 2SC2688 Q502 08-1100-0002 Transistor PNP 2SA1015 Q203, Q204 08-1100-0081 Transistor NPN 2SD667 U401 09-4100-0007 IC TDA2579B U301 09-4100-0119 IC TEA8172 U901 09-4100-0087 IC UC3842 FBT 11-0100-0054 Flyback Transformer T401 41-2100-4009 Driver Transformer T901 11-2100-0095 Driver Transformer R902 01-3203-223J CR 22K 3W R904 01-01 2-*39J CF 0.39 1W R614 01-2003-823J MOF 82K 3W

12

Appendix B. Schematics and PCB Layout Diagram

1. Schematics Page 1 -- Main Board, Video Board.

2. Schematics Page 2 – Power Supply, Video Amplifier

3. PCB Layout -- Video Board, Circuit Trace

4. PCB Layout -- Main Board, Silk Screen

13

12

34

56

ABCD

65

43

21

D C B A

Title

Num

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Revi

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Size B Dat

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Sh

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File

:

G25

G47

K2

HG

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4

HEA

T3

G1 16

J501

CRT

SOCK

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VR5

012M

B

R515

330K

R6 4.7

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C210

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R225

680K

R222

8.2K

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R901

560K

C903

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C904

472/

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D90

13A

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V

C906

47U

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R914

82K

3W

R902

22K

3W

C907

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4 2 16 587 11 12

T901

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35

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1000

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104/

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R909

27K

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R903

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3.9K

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27K

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R907

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1000

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VR2

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VR2

185K

VR6

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R227

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