Space Duel WDT resetting

Hiyas,

Quite some time ago I queried about a watchdog timeout happening around
2x/second on my Space Duel, causing the coin reject relay to clack in time
with it. The unit would work in service mode, though.

It also had issues with alternating 'boop' sounds not firing in test mode.

The sound problem was easy: swap sound chips and the problem did not change
location. Change quad op amp LM324 at D5 (there's another at B5). Done.

Next was to tackle the WDT problem. I thought it might be the 6502 so I
swapped that. No cure. Swapped it back, then swapped AVG chips. The first
AVG chip I had was a 'probable' bad unit from an 'untested' (aka 'bad') board
I bought a couple years ago. I swapped it in, and lo 'n behold it would keep
resetting...but I didn't trust this board so I pulled the AVG chip from
another (bad RAM) board I had. It was definitely a problem with the AVG, as
the SD powered up and ran for some time on this second chip. Unfortunately
this AVG chip was intermittent, and it did indeed fail after it warmed up.
Freez-it spray on the AVG brought it back to life for a few minutes.

I'm about to order one of Clay's AVG replacements - that should fix 'er up!

Just wanted to pass the fix on. I omitted the troubleshooting procedure, as I
was just running in circles w/ my scope...

Cheers,

John
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Received on Thu Feb 5 20:00:08 2004