Electrohome G08 Repair Log

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.


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