Speco Technologies Computer Monitor VM 1201 User Manual

SERVICE MANUAL  
MODEL  
VM-1201  
A0  
REVISION  
DATE  
MAY. 21. 2001  
DOCUMENT NUMBER  
 
2.4 VERTICAL DEFLECTION BLOCK.........................................……………………..………...  
2.5 HORIZONTAL DEFLECTION BLOCK.............................……………………............……...  
3. TROUBLESHOOTING INSTRUCTIONS............................................……………...…….…..  
3.1 NO DISPLAY, NO POWER.......................……………………………………………………..  
3.2 NO DISPLAY, (POWER OK)............…………………………………………………………..  
3.3 NO DISPLAY, (NO ASTER) ……………………………………………..........……………..  
3.4 NO PICTURE OR NO COLOR (RASTERK)..................………………………...………….  
8
8
9
9
9
10  
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 CVBSBNC terminal  
Typecomposite video input  
Synchronous0.3 V  
Level1.0Vp-p  
Luminance0.7V  
PolarityPositive bright  
Impedance75 ohms  
1.1.3 Power Input Requirements  
Operating Voltage Range90 ~ 264 VAC at 50 / 60 ±3Hz  
Input Current at 90 VAC  
Operating0.5 Amps rms. maximum  
Input Current at 264 V  
Operating0.3 Amps rms. maximum  
Power consumption  
Normal operation30 Watts maximum  
1.2 Functional Specification  
The standard conditions for verifying the following specification are as below:  
4
 
• Temperature  
• Magnetic field  
• AC line Input  
• Warm-up Time  
• Ambient light  
25 ±5℃  
No additional magnetic field in near side  
100 ~ 240 VAC ±10%, 50/60 ±3Hz  
30 minutes min. after power on and signal applied  
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 rangeOver 12 dB  
Linearity (cross pattern)  
Horizontal 10% maximum  
Vertical  
10% maximum  
5
 
Picture geometry:≦ 2.5%  
Picture centering:≦ 6mm  
Size stabilityPicture luminance from 5 FL to max., the size shall be less than 2.5%  
(with full white pattern)  
Swing and jittersSwing 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  
• Dimension313mm(H) ×310mm(W) x300mm(D)  
• Net Weight9 Kg  
2. Theory of Operation  
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This section describes each functional block of the monitor.  
2.1 Main Power Supply Block  
• AC power inputAC socket  
• Line input noise / EMI filteringLine filter T902 ;  
X-Cap C901, C902.  
Y-Cap C903, C904, C905.  
• Over current protectionFuse  
• Power on/off controlPower switch  
• AC to DC conversion and filteringDiode D901, Capacitor C906  
• Start-up circuitR914, C914.  
• Main switching power controller, free run oscillation, voltage feed back, switching duty control,  
cycle by cycle over current protection, power MOSFET drivingU901-UC3842  
• Free run oscillationR909, C910.  
Voltage feed back and controloutput voltage control R910, R911 & VR901; gain compensation  
C911& R903.  
• Current sensing and cycle by cycle over current protectionCurrent sensing R904; Noise  
filtering R906, C909.  
• Energy storing and transferringPower transformer T901.  
• Power drivingPower MOS transistor Q901.  
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• Snubber circuitSnubber C907, D902, R902.  
• Primary side self-powering circuitD903,C914.  
• Output 13.5 volts for vertical & horizontal drive circuitsD904, C915.  
• Output 27.5volts for horizontal deflection circuitD906 ,C916.  
2.2 Video input block  
Signal input buffering and switch  
CVBS Input buffer Q201 & R201,R202.  
Video filter & output stage.  
Video inputThrough 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  
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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 controlVR301, R312, R308.  
2.5 Horizontal Deflection Block  
• Horizontal drive bufferingDriving source-U401 pin11. Driving transistor-Q40, to pull high the  
driving waveform to drive the Q401(MOS FET).  
• Horizontal deflectionHorizontal 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  
componentsAC 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 conditionIf 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 circuitsstart up circuit R914,  
and C914.  
3.1.4If no output pulses at U901 pin 6, check and replace U901.  
10  
 
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+27.5Von pin2 of FBT replace D906, C916.  
3.2.2Check driving output voltage0 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 fixU401.  
3.4.2 Vertical raster abnormal (one horizontal line, size too small or fold back on top / bottom) --  
check and fix14V supply at U402 pin2, if has voltage check and fix U301.  
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Appendix A. Spare Parts List  
Location  
Parts Number  
28-1100-0006  
Description  
Fuse, 2A/250V, slow blow  
Diode 3A, 600V, RS407  
Diode, 1.5A, 800V, BA159  
Diode, 3A, 800V, FR107  
Diode, FR1005  
F901  
D901  
06-3100-0005  
06-1100-0001  
06-1100-0023  
06-1100-0014  
06-1100-0058  
08-3100-0011  
08-1100-0003  
08-1100-0001  
08-1100-0002  
08-1100-0081  
09-4100-0007  
09-4100-0119  
09-4100-0087  
11-0100-0054  
41-2100-4009  
11-2100-0095  
01-3203-223J  
01-01 2-*39J  
01-2003-823J  
D902  
D501, D502  
D903, D904, D301  
D906, D401  
Diode, 2A, 600V, FR205  
Power MOS 2SK2996  
Transistor NPN 2SC1815  
Transistor NPN 2SC2688  
Transistor PNP 2SA1015  
Transistor NPN 2SD667  
IC TDA2579B  
Q901  
Q201, Q202, Q206, Q402, Q501  
Q205  
Q502  
Q203, Q204  
U401  
U301  
U901  
FBT  
IC TEA8172  
IC UC3842  
Flyback Transformer  
Driver Transformer  
Driver Transformer  
CR 22K 3W  
T401  
T901  
R902  
R904  
CF 0.39 1W  
R614  
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  
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G 4  
G 2  
7
6
5
G 1  
1
D
S
V C  
C / t R t  
7
5
4
8
G N D  
f e V r  
 
3
2
1
C 2 0 4 1 / 6 V 1 0 U  
R 2 1 1 3 K 3 .  
R 2 0 9 1 2 0  
C 1 2 8 S 1 5  
2 0 Q 3  
5 / 0 V 2 U 2 .  
C 2 0 5  
1 0  
1 1  
1 2  
1 3  
1 4  
1 5  
1 6  
1 7  
1 8  
9
8
7
6
5
4
3
2
1
8 1 . W  
R 3 0 6  
C 4 1 5 0 . 1  
3
8
6
4
2
 

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