Speco VM-1201B User manual

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
TheVM-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
2.3.6Horizontal 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.
3.1No Display, No Power
3.1.1First of all, turn power off, use multimeter to check Q901, and R904, replace if bad. Turn
power on after that.
3.1.2Check 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
3.1.3Check 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.
3.1.4If no output pulses at U901 pin 6, check and replace U901.
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3.1.5If 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.
3.2No Display, power output normal.
3.2.1Check and fix FBT B+：If no B+（27.5V）on pin2 of FBT replace D906, C916.
3.2.2Check driving output voltage：0 or very low check and replace Q402, Q401.
3.2.3Power off monitor. Check yoke connection. Use multimeter to check D501, D502, D401, Fix
if any is bad.
3.2.4Power on, check voltage at pin10 of U401 if no voltage, check and fix Vertical circuit B+,
D904.
3.3No Display (No Raster).
3.3.1Check yoke connection.
3.3.2Check CRT board and verify CRT heater is on.
3.3.3Check G2 voltage if fail, check and fix FBT or D502.
3.3.4Check K (cathode) voltage at negative of D501 about 150V, If no voltage output Check and
replace D501 and C501.
3.4Vertical Deflection Failure
3.4.1Vertical 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

123456
A B C D
6
54321
D
C B A
Title
Number RevisionSize
B
Date:Sheetof File:
G2 5
G4 7
K
2
HGND
4
HEAT
3
G1
16
J501 CRT SOCKET
VR501 2MB
R515 330K
R6
4.7 1/4W
1 2 3
W204
C210 47U/200V
R225 680K
R222 8.2K 2W
R223
1.5K 1/2W
R224 150K C214
1U/25V
1 2 3
W205 R221
1K
Q205
2SC2688
C217 47U/25V
B+ 12.9V S201
SPARK GAP
PLUG AC SOCKET
W902 F901
2.5A/250V
C901
.1U/250V
T902
EE-25
C902
0.1U/250V
R901
560K
C903 472/400V
C904
472/400V
D901 3A/600V
C906 47U/400V
R914 82K 3W R902
22K 3W
C907 .01 1KV
4 2 1 6 5 8
7 11
12
T901
ERL-35
D902 BA159
GND 5
VC 7
COMP
1
Vfb
2
Vref
8
Rt/Ct
4
OUT 6
Ise 3
U901
IC3842
D905 1N4148
R905 18
R906
1K
C908
472 /1KV
G
S D
Q901
2SK2996
R904
.39
C909 1000P
C912
104/50V R909
27K
C910
562/100V
R903 1M
C911
PEI 103
VR901
SVR 1KB
R911 3.9K R910 27K
D903
FR105
C914
EC 100U/25V
C914
EC 100U/25V
R908
47
R907
390
D906 HER205
C916 EC 2200U/50V
27.5V
C915
1000U/25V
D904
FR105
L901
56UH
12.9V
12V
R912
10 2W
D907
FR105 C918
EC 1000U/50V
OPTION
VR201
500
VR218
5K
VR603
2K
VR203
3K
R224 100
VIN
R226 15K
R225
4.7K
R228
270
R227 270
R413
22K
V-POSI H-POSI
POWER BOARD
VR BOARD
CRT BOARD
VM-901B/1201/1501B POWER/BCRT/B VR/B
SYNC+
SYNC-
GND CONT
13.5V
FUNCTION
OPTION
W504(PIN5)W504(PIN2)

12345678
A B C D
8
7654321
D
C B A
Title
Number RevisionSize
Date: File: Drawn By:
1
2
3
4
5
6
7
8
910
11
12
13
14
15
16
17
18
U401 TDA2579
C411 103
R217 15K
R410 2.2K
R406 18K R416
680
Q402 2SC1815 R417 1K
C407 100U/25V
R418
47
Q401 IRF740
R408 12K
C408 1U
R411 33K
C410.15
C409 2700P
R411 30K
VR401 H-HOLD
R409 270
C416 22U/50V
R413 5.6K
R301 4.7K
C302 472
C309
4.7U
R315 470
R311 330K R308 100
R306 1.5 1W
VR301
300B V-SIZE
R312
33
C301 .15
5
7 1
4
8 3
6
2
U301
IC TDA8712
R302 2.2K R303
5.6K
C303 .047
C304 .047 R304
1K
C305
100U/35V
D301
1N4002
R313 2.7 2W
12.9V
C304 2200P
C306
104
R305 1
R307
180 1/2W
C311 .022
C402 150P
R401 820
R403 5.6K
C402
150P
C404
22U/25V
R404
22
C403 2.2U
C406
.1U
C405 2.2U
R405 1.2K
C308
1000U/25V
R306
1.8 1W
1 2
W201 VIDEO IN
R228 1K
C201 47U/16V
Q201 2SC1815
R203 470
R202 15K
R201 12K
C202 220U/16V
1 2 3 4 5 6 7 8
W504
Q204 2SC1815
R219 330
C206 C560P 100V
R510 1.2K
Q501 2SC945
R513 1.2K R511
1.8K R512 1K
Q502 2SA733
R214 1.8K
R213
10K
D201
1N4148
1 2 3
W503
14V
R210 12K
R2113.3K
Q203
2SC1815
Q202 2SC1815
R212 680
R209120
R208 150
C205
2.2U/50V
R207 120
R205 12K R206 2.2K
C203
22U/25V
C20410U/16V
VR201
50K BRIGHT
Q206 2SC1815
R220 2.7K
R218 6.8K
C208 4.7U
R217 15K
C414 273/400V
D401 FR205
R506 8.2 2W
1 2 3 4
W501
DY
1 2 3
W502
D502
FR107
D501
FR107 C501
10U/250V
C502
223/630V
L404 C501 10U/250V
H.V
L402
12UH
12.9V
3
1 2
7
4
5
6 8
C? FBT-3
B+ 27.5V
1 2
J? 8/1W
1 2 3 4 5
6 7 8
U701 LM386
C705 470U/25V
R703 10
C704 473
R704 33 2W
C706 1000U/16V
12V
C703 100U/16V
1
2
3
W702
1 2
W701
VR? 50KB
C702 562
R702 8.2K
C701
22U/25V
R701 10K
VM-901B/1201/1501B W/AUDIO MAIN BOARD