Space Duel WDT (clacking) and A/V problems solved!

 A couple problems I had with my Space Duel came to haunt me years later
when I finally got around to looking at the machine.

 It would come up in test mode and go through all the different stages,
but with bad (clipping) X-axis video. Audio only. And only one
channel. I did swap the POKEYs, but the problem didn't follow. If the
game was not in test mode, it would reset and click the coin relays
about every 1/2 second due to a watchdog timeout.

 This is what I did for each repair:

  Watchdog timeout: Replace CPU 6502A at C2
  Missing Audeo: Replace Audio Op Amp LM324 at B5 (did D5 as well for
good measure)
  Poor X-Axis: Replace Op Amp TL082 at D/E 11 (output stage of X-axis)

 I hooked up the monitor after I was confident in the output quality
while viewing on my dual channel scope...but the monitor didn't power
up. Apparently the fuses failed on the monitor, so I replaced them.
They didn't blow, per se, rather slid out from one end. I assume due to
heat. I've never seen that happen before, but what the heck - there's a
first time for everything.

 It works wonderfully now. I did purchase one 'used' SD board last
year, however both POKEYs and the AVG were bad on it and the EPROMs had
bitrot. At least I used the CPU from it!

 Cheers,

 John

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Received on Mon Dec 23 17:41:56 2002