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7-8
Video Troubleshooting Table
SYMPTOM CAUSE REQUIRED ACTION
Power problem
Verify connection of AC Power to video monitor.
Inspect CRT neck in dim light. Glowing filament
near CRT base proves that some monitor
circuits receive power. Still, voltages or signals
may not be normal.
Faulty wiring
1. Turn off VGM power. Verify that video signal and
Remote Adjustment Board connectors seat
properly on Video Monitor Board.
2. Assure that video cables connect to circuit
boards.
3. Assure that no wires are caught on chassis or
mounting brackets.
Improper monitor
adjustments
Check that BRIGHTNESS (intensity) and
CONTRAST are set above their minimum
levels.
•
Monitor appears non-
functional
•
Audio is present
•
VGM (video game machine)
controls operate normally
Faulty monitor
circuitry
1. Examine AC line fuse on Video Monitor Board. If
fuse is faulty, replace it with identical fuse.
2. If fuse is good: Verify that video monitor operates
correctly by placing it in working VGM.
3. If monitor is bad: Check monitor power supply.
4. If power supply is good: Check monitor
horizontal output transistor and related circuitry.
WARNING: HIGH VOLTAGE.
VGM monitors
generate and store potentially lethal high
voltages.
Avoid touching any part of the monitor until power has been off for some
time. A picture tube can maintain a hazardous charge for up to several days. Only
qualified technicians should service monitors. Turn off the power, unplug the VGM and
discharge the CRT before attempting service. Even properly discharged tubes can
revert to a highly charged state, without reapplication of power.
WARNING:
In normal operation, the monitor doesn’t require isolation from AC line
voltage. During bench servicing, you may need to operate the monitor outside the
cabinet. If you do, isolate the monitor from line voltage with an isolation transformer.
CAUTION:
Don’t operate the monitor without the Remote Adjustment Board.
Typical Cutaway Rear View