SERVICE MANUAL
MODEL
REVISION
DATE
DOCUMENT NUMBER
：
：
：
：
VM-1201
A0
MAY. 21. 2001
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 V
‧ Input Current at 90 V
AC
Operating：0.5 Amps rms. maximum
‧ Input Current at 264 V
Operating：0.3 Amps rms. maximum
‧ Power consumption
at 50 / 60 ±3Hz
AC
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 V
•
Warm-up Time ：30 minutes min. after power on and signal applied
•
Ambient light ：400 to 600 lux.
±10%, 50/60 ±3Hz
AC
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
D
6
VR501
2MB
G4
R515
330K
C210
47U/200V
54321
123
W204
7
6
5
R225
680K
R222
8.2K 2W
G2
K2HGND4HEAT
R223
1.5K 1/2W
C214
R224
G1
3
1U/25V
150K
CRT BOARD
C
1
J501
CRT SOCKET
R6
4.7 1/4W
S201
SPARK GAP
OPTION
2SC2688
C217
Q205
47U/25V
R221
1K
B+ 12.9V
123
W205
12.9V
B
H-POSI
V-POSI
R228
FUNCTION
VR BOARD
W504(PIN5)W504(PIN2)
R226
VIN
GND CONT
3K
VR203
22K
R413
R227
270
2K
VR603
270
R225
5K
VR218
15K
500
VR201
R224
100
A
VM-901B/1201/1501B POWER/B CRT/B VR/B
Number RevisionSize
B
Title
Date: Sheet of
File:
4.7K
27.5V
C916
EC 2200U/50V
D906
HER205
7
T901
6
5 8
C907
.01 1KV
R902
22K 3W
R914
82K 3W
2.5A/250V
C906
EE-25
C901
.1U/250V
D901
3A/600V
C903
472/400V
0.1U/250V
C902
T902
F901
W902
R912
10 2W
12V
L901
56UH
13.5V
FR105
D904
4
47U/400V
1000U/25V
C915
12
11
ERL-35
2
1
D902
BA159
FR105
D903
EC 100U/25V
C914
C904
472/400V
560K
R901
EC 100U/25V
C914
OPTION
C918
EC 1000U/50V
D907
FR105
C908
472 /1KV
S D
R904
R905
OUT
COMP1Vfb
18
IC3842
.39
1K
R906
C909
1000P
3
Ise
Rt/Ct
4
R909
Vref
8
2
C912
SVR 1KB
VR901
R911
3.9K
G
Q901
2SK2996
1N4148
D905
6
VC
7
GND
5
U901
R903
1M
PEI 103
C911
R910
27K
27K
104/50V
POWER BOARD
562/100V
C910
SYNC+
47
R908
390
R907
SYNC-
1 2 3 4 56
PLUG AC SOCKET
D
C
B
A
D
8
C
B
J?
8/1W
1
2
C704
C705
470U/25V
R704
33 2W
12V
U701
LM386
123
678
4 5
473
R703
10
A
C706
1000U/16V
C703
100U/16V
123
DY
W501
123
12.9V
4
L404
C501
10U/250V
12UH
L402
B+ 27.5V
R220
2.7K
Q401
IRF740
47
R418
R417
1K
R408
12K
C408
R409
C416
1U
270
22U/50V
R413
5.6K
Q402
2SC1815
C407
100U/25V
R416
680
R410
2.2K
11
R406
18K
12
13
R411
33K
14
C410.15
15
16
17
18
15K
R217
C411
103
C409
2700P
R411
30K
VR401
H-HOLD
7654321
W502
C501
7
2SC1815
330K
10U/250V
FR107
8
D501
FR107
D502
FBT-3
3
5
4
1234567
VR201
10K
R213
R219
C206
C560P 100V
150P
C402
C404
22
R404
R403
5.6K
C405
2.2U
R405
1.2K
C402
150P
C301
.15
R301
C302
R315
470
R308
100
R306
1.5 1W
2
1
W702
C414
273/400V
D401
FR205
R210
12K
R212
680
50K BRIGHT
D201
330
22U/25V
4.7K
472
4.7U
C309
C205
R205
1N4148
C403
2.2U
14V
.1U
C406
12.9V
R313
VR301
300B V-SIZE
2SC1815
Q203
2.2U/50V
12K
C203
2.7 2W
R312
R701
10K
VR?
50KB
C20410U/16V
R2113.3K
R209120
R208
150
Q202
2SC1815
R207
120
R206
2.2K
22U/25V
Q201
2SC1815
R201
12K
R512
1K
C311
.022
C305
100U/35V
6
2
D301
1N4002
7
R303
5.6K
R302
2.2K
33
223/630V
C502
H.V
6
C?
3
1
2
R506
8.2 2W
8
W504
Q206
2SC1815
R218
6.8K
Q204
C208
4.7U
R217
15K
123
W503
R401
820
9 10
8
7
6
5
4
U401 TDA2579
3
2
1
R311
C702
562
R702
8.2K
C701
22U/25V
1
2
W701
C202
220U/16V
R203
470
R202
15K
R228
1K
1
C201
47U/16V
Q502
2SA733
Q501
2SC945
R307
180 1/2W
5
R305
U301
IC TDA8712
1
2
W201
VIDEO IN
R214
1.8K
R511
1.8K
R510
1.2K
R513
1.2K
1.8 1W
R306
C308
1000U/25V
104
1
C306
8 3
4
C304 2200P
C303
.047
1K
R304
C304
.047
Number RevisionSize
VM-901B/1201/1501B W/AUDIO MAIN BOARD
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