Re: Battlezone AVG problems...

jwelser@ccwf.cc.utexas.edu wrote:
>
> 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

I had lots of practice with Battlezone. :-( On the three boardsets I
worked on, one of them had a bad DAC, one had a bad analog switch, and
the other had bad op-amps. The biggest failure I've found on the Atari
vectors has been the op-amps (if I include all Atari vector games I've
worked on).

I understand your hesitancy to just go bonzaii and replace everything,
but unfortunately, those parts that are left are still big culprits in
their own rights and need to be checked. Though, I'd start with the
op-amps first.

In fact, I just had a speech failure last weekend on my Black Knight
pinball. It turned out to be a 1458 op-amp. At least there are no
analog switches to fool with. I haven't figured out how to test those
things appropriately other than to "swap and see" if it works.

Joel-
Received on Wed Oct 29 13:26:33 1997