Re: Tempest: Mathbox error on AVG board

Go reflow your headers. They tend to make contact then break contact at
random intervals. :-(

On 2/24/2013 1:46 PM, Ian Eure wrote:
> I have a Tempest PCB I'm working on, and I'm stumped. The game boots up and plays, but vectors are scrambled. Self-test reports a mathbox error. I swapped a known good aux board and interconnect, and it still reports the error, so the problem is on the AVG board.
>
> I have continuity on all the proper pins to the right places. I didn't reflow the headers, but they appear fine. Probing all the interconnect pins reveals nothing unusual, nothing is stuck and everything that should have activity does. Initially, there were some spurious noises in self-test mode, which made me think there may be a short somewhere, but I probed every combination of pins and found nothing. This symptom subsequently vanished. I have no explanation for why.
>
> Reading through the schematic, AVG<->AUX communication is handled via a LS244 at B/C1 and LS245 at H2. I socketed and replaced both, but the error persists.
>
> I see that a 244 @E2 & 245 @F2 share the data bus with H2, and E2 is driven by another 244 @A/B1, so those are my next suspects, but I thought it was time to check in first. Has anyone else seen similar issues?
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Received on Sun Feb 24 17:08:37 2013