More Battlezone repair puzzles

From: Commander Dave <cmdr-dave_at_spamcop.net>
Date: Thu Aug 22 2002 - 17:27:24 EDT

I am still having a devil of a time with an AUX BD that I am repairing on a Battlezone. The symptoms are a mathbox timeout ("T") in the diagnostics and in game mode when you press start, you hear the tank rumble for about 6 seconds before it quits. There is no change when you move the controls.

I have done most of the obvious, including replacing the 40 pin sockets with machined sockets, and verified that all socketed chips are good (part swapping with known good board). Still no luck...

So, I broke out the logic probe. Found that the STOP line is being held high (active high). Without going into lots of detail, I removed and tested (again by swap) many of the support chips. This would include C3 and C4. Still no luck. One of the things I noticed that was different than a working board was that on chip C3 the signal is being held HIGH, when on a working board it should be pulsing. Everything coming in and out of the rest of the pins is OK... replacing the chip did not help. Also on pin 9 of IC C5, is HIGH, which is the STOP line.

I did find other abnormalities with E1, which replacing the chip cured those, but the pesky problem above still remains. Can someone look at the schematics and give me an idea where to look why pin 9 or C3 being held high?

If needed I can email the mathbox schematics with the pin levels marked (LOW, HIGH or PULSING).

Thanks for ANY help,
-Commander Dave

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Received on Thu Aug 22 14:45:39 2002

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