Symptom: Monitor sounds like it is deflecting correctly, but there is no HV.
Actions taken: Looked at voltages at the HV 10 pin connector. 126VDC is missing.
Looking at the schematics, it looks like the voltage comes off of part of the
voltage rectifying circuit, then is put through a voltage trippler circuit, and
then sent to the HV unit and to the HV regulator board which regulates the 126VDC
down to 100VDC. This is a simple circuit, so I test the parts, and everything
looks good. I check the capacitance of the two large capacitors in the circuit,
and they look good. However, I wiggle one of them and realize that it's legs are
loose. The capacitor has broken it's solder joints on the board. I resolder the
capacitor and the monitor now works.
Symptom: Monitor sounds like it is deflecting correctly, but there is no HV.
Actions taken: Looked at the voltages at the HV 10 pin connector. The +9.1VDC
is missing. Taking a look at the schematics reveals that the AC is rectified
and sent through a TIP29B (the one on the heat sink). I verify that the other
voltages are present. The others look good, so I replace the TIP29B. The monitor
now works.
Symptom: Monitor sounds like it is deflecting correctly. Neon bulbs on the neck
board are lighting, and sparking is seen in the tube.
Actions taken: Verified the voltages being sent to the neckboard are good.
Test the tube on a tube rejuvenator and it indicates a short. Tube is ruined,
so it is thrown away (after breaking the tube's neck).
Symptom: Monitor sounds like it is deflecting correctly, but there is a deflection problem in
two of the axis, resulting in mostly 1 quarter of the screen being displayed. However, the
heat sink deflection transistors are known good. Problem is associated with the deflection
board only.
Actions taken: Verify the +63V/-63V on the board. Most likely
transistors on the deflection circuitry.
Symptom: Eliminator: during demo mode, things entering the screen from the right side (such as
text and enemy ships) tend to come on the screen weird (or like a point in from the edge,
then goes back out to the edge, then in again). Seems like a slight
deflection problem, but everything else displays fine.
Actions taken: The capacitors on the input protection board (the small 1" x 3" pcb which
connects between the game board and the monitor) are going bad. Replace them with 10uf 50VDC
capacitors.
Symptom: Replaced everything but custom chip and it still doesn't work
Probably the custom chip.