Battlezone AVG problems...

Hey all,

        I've got a Battlezone board which appears to have AVG problems.
Everything plays fine, but I get no video (in a known good monitor.) It
looks like the culprit is the Yout, which sits around 0VAC. The Xout is
around 3VAC. I tried to debug this, but I really didn't get anywhere. I
checked that the inputs to the DACs were not stuck, and that the outputs
of the DACs weren't at 0 (They were around 3 or 4 VAC when the game was
is self-test mode.) I checked to make sure the pots on the board weren't
open, etc. The game passes all the self-tests.

        I normally would just "shotgun" everything that's left (I think
there are about 6 other chips in the AVG, besides the 2 DACs,) but I
really hate desoldering from Atari boards (They've got to be the cheesiest
boards I've ever worked with) so I'd like to minimize the desoldering if
possible. Any ideas of what's more likely to go bad than anything else (I
think I'm left with 2 Op-amps per channel and 1 analog switch per
channel?) or how I can test the intermediate voltages?

Thanks,

Joe

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Joseph J. Welser jwelser@ccwf.cc.utexas.edu
Design Engineer -- Crystal Semiconductor Corporation
Ph.D. Student in E.E. -- University of Texas at Austin
Work: jwelser_at_crystal.cirrus.com http://www.crystal.com
P.O. Box 17847; Austin, TX 78760
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Received on Wed Oct 29 13:07:03 1997