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Tatung Vibrant VM78F Service Manual

17-inch color monitor
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Service Manual
17-inch Color Monitor
VM78F

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Summary of Contents for Tatung Vibrant VM78F

  • Page 1 Service Manual 17-inch Color Monitor VM78F...

  • Page 2: Table Of Contents

    VM78F Table of Contents 1. Precautions ......................... 2 2. Product Specifications ....................5 3. Operation Theory .....................10 4. Alignments and Adjustments ...................15 5. Troubleshooting......................19 6. Recommended Spare Parts List ................26 7. Block Diagram......................28 8. Exploded Diagrams ..................Inserted 9. PCB Diagrams ....................Inserted...

  • Page 3: Precautions

    VM78F 1 Precautions Follow these safety and servicing precautions to prevent damage and to protect against potential hazards such as electrical shock and X-rays. nonmetallic control knobs, insulating materials, 1-1 Safety Precautions cabinet backs, adjustment and compartment covers or shields, isolation resistor-capacitor networks, mechanical insulators, etc.

  • Page 4: Servicing Precautions

    VM78F 1-1-3 Product Safety Notices Many electrical and mechanical parts in this chassis have special safety-related characteristics which are often not evident from visual inspection, the protection afforded by them may not be obtained by replacing them with components rated for higher voltage, wattage, etc. Before replacing any of these components, consult the Recommended Spare Parts List given at the end of this manual.
  • Page 5 VM78F Plug monitor power cord to the Hi Pot tester terminals. Turn on tester and watch the indicator or beeper. If the indicator lamp lights, or beeper beeps, the test fails. 1-4 Ground Continuity Test 1. Test Equipment AC low ohm tester TOS-6100 or equivalent approved equipment.

  • Page 6: Product Specifications

    VM78F Product Specifications 2-1 Specifications 17-inch (15.8-inch Visual image area), sloted mask, 90 degrees Picture Tube deflection, dot type black matrix, medium short persistence phosphor, dark tint, non-glare/ anti-static screen, 0.25 mm(FNSL/T) dot pitch VGA, Super VGA, 1024x768@60/70/75/85/100 Hz Scanning Frequency...
  • Page 7 VM78F 2-2 Signal Cable Pin Connections Table 2-2. Signal Cable Pin Assignment Signal Signal Red video 9 ** Green video Digital Ground Blue video Ground Ground H-Sync Red ground V-Sync/VCL Green ground Blue ground Note * This pin is used for selftest detection. Connect this pin to ground at the PC end.

  • Page 8: Timing Chart

    VM78F 2-3 Timing Chart This section describes the timings that the computer industry recognizes as standard for computer-generated video signals. Table 2-3. Timing Chart MODE H. Dots 1024 1024 1280 1024 1280 1280 V. Lines 1024 1024 H. Freq. (KHZ) 31.47...
  • Page 9 VM78F 2-4 Display Power Management Signal (DPMS) Note: These power-saving states exceed the Environmental Protection Agency (EPA) Energy Star requirements. Table 2-4. Display Power Management Signal (DPMS) State LED Color H-Sync V-Sync Power Consumption Green Pulse Pulse Normal Amber No Pulse No Pulse <5 watts...
  • Page 10 VM78F 2-5-1 TCO 95 Version (Optional) The TCO 95 scheme is for international and environmental labelling of personal computers. The labelling scheme was developed as a joint effort by the TCO (The Swedish Confederation of Professional Employ ees), Naturskyddsforeningen (The Swedish Society for Nature Conservation) and NUTEK (The National Board for Industry and Technical Development in Sweden).

  • Page 11: Operation Theory

    VM78F 3 Operation Theory This is a fully digital controlled multi-sync color monitor that is compliant with DDC1 and 2B Plug and Play VESA standard and offers the following main features. 3-1 Main Features 1. Simplified design with minimum components.
  • Page 12 VM78F 3-3 Deflection Section 1. I C -- autosync deflection controller is TDA4841. 2. The TDA4841 is a high performance and efficient solution for autosync monitors. All functions are controllable by I C bus. SDA and SCL signals coming from microprocessor feed to pin 19 and pin 18 to control all functions.
  • Page 13 VM78F 3-3-6 G1, Blanking and Brightness 1. The vertical blanking signal comes from pin 16 of TDA4841. This pulse through Q405 amplified and converted into negative pulse and sent to G1 for vertical blanking. 2. In protection mode or an out-of- range situation HUNLOCK will send 5 V pulse to cutoff Q407, then G1 will go down to -150V.
  • Page 14 VM78F 3-4-4 Auto Degaussing When S801 turns on, pin 14 of I701 will send a signal to Q802 and turns on RL801 for degaussing. After 4 seconds, it will turn off RL801 automatically. 3-4-5 PWM Control 1. Start Up The I801 (5S0765C) gets power from R807, R808, C830 and pin 3 voltage reaches 15 V for starting up.
  • Page 15 VM78F 3-5 Video Amplifier Section 1. RGB signal inputs are terminated by R501, R531 and R561 then pass through the coupling capacitors C503, C533 and C563 to IC501 LM1267 preamplifier. 2. The amplifier RGB signals (0~3 Vpp) are adjusted by I C bus, I501 pin 23 is for clamp pulse which comes from pin 16 of TDA4841 to set up equal clamp level.

  • Page 16: Alignments And Adjustments

    VM78F 4 Alignments and Adjustments This section of the service manual explains how to make permanent adjustments to the monitor settings. 4-1 General Adjustments 4-1-1 Adjustment Conditions a) Power Supply Apply AC 115 V or 220 V b) Warm-up Time The monitor must be powered on for 15 minutes before starting any alignment, but requires 30 minutes of warm-up time for convergence adjustment.

  • Page 17: Alignment Procedures

    VM78F 4-2 Alignment Procedures 4-2-1 High Voltage Adjustment CONDITION Press key simultaneously when switching the power “On”. Display image : No video (86kHz Mode) PROCEDURE Connect DC meter to TP002 and adjust HV (icon) Obtain a DC voltage of -152 ± 0.2 V DC (Sampo FBT) for CPT CRT M41AGE93X76 (TCO).
  • Page 18 VM78F 4 Full white ABL setting CONDITION Display image : full white pattern Set Brightness to cutoff and Contrast to maximum. 4-b. Adjust ABL to Y=29FL ± 1FL. 4-c. Check the white balance at 5FL and 30FL. 4-d. Repeat all the procedures in 4-2-2 section until the best white balance is obtained.
  • Page 19 VM78F 3. Rotate the individual rings of 4-pole convergence magnets by changing the spacing between the 2 tabs to converge the vertical red and blue lines at the center of the screen. 4. Rotate the pair of rings of 4-pole convergence magnets by maintaining spacing between the 2 tabs to converge the horizontal red and blue lines at the center of the screen.

  • Page 20: Troubleshooting

    VM78F Troubleshooting 5-1 No Raster No Raster Measure voltage of B+ at T402 pin 2 on PWB-MAIN Normal High (56 V, 31.5 kHz) (75 V or more) Check voltage of Check I401, cathode, heater, I703, R719, C741, Short Circuit Grid 1, Grid 2, etc.
  • Page 21 VM78F 5-2 OSD Abnormal OSD Abnormal Check I502 pin 9, 4 Put on is 5V and pin 5, 10, 7, 8 I502 missing? Check R517, L514, R527, R523, R524 Replace them Check P502 Replace it Replace I502...
  • Page 22 5-3 Function Key Abnormal Function Key Abnormal Put on Check I701 and I701, I703 I703 missing? Power ON/OFF again and Replace X701 check X701, oscillator Check Replace I703 or do I703 EEPROM content ATE again Replace I701 and check Replace I701 uP OK? Check Check...
  • Page 23 5-4 No Vertical Scan (Raster is one horizontal line) No Vertical Scan Check I301 voltage of Ckeck or replace pin 1 is 12V, pin 4 is I301. -11V, pin 2 is 40V? Check Check R312, R307, pin 5 O/P waveform at R306, R313, R308, I301 ? R315, R316...
  • Page 24 5-5 Out of Horizontal Synchronization Out of Horizontal Synchronization Check or replace Horizontal the signal cable or sync present at H. sync pin 41 pin 15 of I401 of I701. Check I401 pin 8 H. output Check or replace frequency & pin 29 I401, C406 waveform Check Q401,...
  • Page 25 5-7 R.G.B. Video Amplifier Abnormal RGB Video AMP Abnormal Check Check or replace the waveform at I501 pin 5, 6 and signal cable or I501 Check waveform at I501 Replace I501 pin 18, pin 19 and pin 20. Check I502 pin 1, 2 and 3 collector Replace I502 voltage (normally about 70V) &...

  • Page 26: Recommended Parts List

    Recommended Parts List Note:1. The components identified by “ “ mark are critical for X-ray safety. Replace these with exactly the same parts specified. Location Part Number Description Q401 6421002705 TR NPN KSD1616A G TA C808 6312618102 ALU uF 180 400V F 85C 25x35 D801 D802 6412010907 DIODE LT2A06 T52 2A/800V...

  • Page 27: Recommended Spare Parts List

    Location Part Number Description Q419 6422006000 TR NPN 2SD2012 TO-220(IS) Q420 Q421 6426010500 (S1) FET N-CHNL IRF630MFP/IRFS630A Q430 Q403 6426006400 (S0) Q451 6426006300 FET N-CHNL IRFS634A FAIRCH 11d R803 6203080017 POSISTOR & OHM DGC2R08M R804 6201100012 THERMISTOR 10 OHM 3A P=5 UEI R802 6221127852 MOF OHM 0.27 1W J HOR...
  • Page 28 R DAC P501 G DAC B DAC LM2479 R, G, B I502 I501 BUFFER Video AMP PRE AMP & DC LM2467 LM1267 RESTORE R G B SW 5 V 11.6V MTV021 P503 P502 BLANKING BRIGHTNESS CONTROL & 25.6KV SPOT KILLER HFLB DRIVER -150V...

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