Tempest board suddenly making bad vectors

Hello,

My friend and I thought we were pretty much done with restoring his Tempest
this evening. I was play testing it when all of a sudden, the vectors got
all wonky. Sigh. It seems to be some kind of up deflection problem.

Luckily, my friend was filming me playing the game when it happened, so you
can see that here:

   http://www.youtube.com/watch?v=KzoSp907Vlg

We then took a video of some of the test screens. You can see them here:

   http://www.youtube.com/watch?v=RzKX2D6hqOE

I pulled out my Wico x-y pattern generator, and the monitor is fine, so the
problem is with the Tempest board.

Any clues where I should look? From what I've read online, I should start
with the DACs, analog switch and op-amps. Anything else I should look for?

Thanks!

___
Ken
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Received on Thu Aug 25 17:24:17 2011