TECH FIX: Cutoff in an AA

I just fixed my AA which had a "cutoff" problem wherein after
5-10 minutes of play, the +5V would die to under +1V.

SYMPTOMS:
Game would boot up fine and +5V would be regulated at around +4.9V
on the CPU board. After playing several games, the +5V began to rise
suddenly to about +5.5V and then decay back slowly to +5V. Then after 10
seconds of this, it died to under +1V. The game would then "cutoff".
Recycling the power brought the game back up but then the symptoms would
return.

ANALYSIS:
Testing multiple known working CPU/Sound boardsets proved that the
"cutoff" would still occur. Ripoff boards lasted longer before "cutoff"
than
AA boards. Perhaps RO draw less power on the +5V? Needless, this
proved that the problem existed in the power supply. Luckily, the CONDOR
and NATIONAL power supplies are easy to debug. Mine is a NATIONAL
but the circuits are pretty much the same.

FIXES:
Removing the power supply revealed three problems.
1. there were cracked solder joints on the 12pin header. RESOLDERED.
2. the by-pass transisted mounted to the metal case was not torqued down
tight enough. RETORQUED.
3. replaced the uA723 voltage regulator IC with a 14 pin socket and a
Motorola
MC1723 equivalent. REPLACED.

Humm, the 3-R's of fixing a game. :-)

SUMMARY:
The probable root cause was the 723 IC. This power supply was completely
original and had had no maintenance nor repair over its lifetime (visual
assumption).
To fix your PS properly, check the above and perhaps give it a "cap kit"
(just
like one would do in a monitor).

SPW
Kanata, On
CANADA
Received on Sun Aug 29 08:33:47 1999