Display problem with Lunar Lander board

I have a Lunar Lander board - only runs in test mode (apparently some PROMs
are missing (H1 and F2), when they're not as they're part of F1 when using
2716 EPROMs). Anyway, that's irrelevant right now as I have an even more
irritating fault.

The display in test mode used to be fine - nice and steady, etc. However,
in between one of my ROM swapping episodes it's gone screwy - it very
rapidly flashes and I get a few diagonal lines on the screen, BUT I also
get the text that should be there as part of the test. The monitor is fine
(it's okay with my other boards). It does though sound most unhealthy when
it's in this 'flashing' state though. Understandable really. :) I'm sure
it's not the ROMs in this case as have tried others with the same results.

Other 'adjustments' which I've made during the testing process are as
follows: straightened out the X and Y Gain and Zero pots, the purple caps
near them (all were flattened to the board), straightened out a couple of
bent pins on the solder side, and re-soldered one dodgy looking joint.
Surely though none of these 'adjustments' would have caused the problem
though? Yeah, I know, they might well have done, but it seems unlikely.

Maybe an IC that was previously in a half dead state has suddenly given up
the ghost as a result of being used for the first time in years?

Ah well, back to the schematics ..........

Phil

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Received on Tue Feb 19 02:48:49 2002