Re: star wars problems

I have seen this foldover problem on other vector games and I think I can
suggest a couple of things to try.

*) Make sure it is not in the monitor. This can be done by substituting
another monitor or using an X/Y scope on the video outputs of the AVG board.

*) If it is on the AVG board, use the schematics and probe around upstream
and try to find a point at which the foldover is gone. It is possible to
connect both oscilloscope probes to upstream locations in the X and Y video
output circuits and still get an image, although you will need to crank up
the sensitivity of the 'scope.

*) Be certain you don't have a broken leg on an adjustment pot. I forget
if Atari used flush-mount pots on all SW boards...

*) If it's on the board: Chances are the foldover is caused by either a bad
op-amp, or by a flaky 1495. The op-amps are cheap and readily available,
and direct substitution can eliminate those. If you isolate it to the
1495s, but do not have replacements at the moment, you can at least verify a
bad one by swapping the chips out with each other between X and Y channels.
If the foldover switches from one axis to the other, you've found it.

Use the probe, Luke. :)

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Received on Sun Oct 13 18:24:49 2002