Maker Pro
Maker Pro

APC SUA1500RM2U

Hello all, we usually have a pile of these at work in the to-be-
repaired bin. Most of the time it's just the batteries, but I have
one that needs a little love. It had a bad fan- a simple problem.
After replacing the fan with a similar type and powering the unit back
up, one or more relays clicked rapidly and then Q42 and Q44 burned.
The fan also tried to spin up then stopped.
In all schematics I've found these transistors switch the relays, but
on the board there are clearly different transistors (Q11,Q18,Q23,etc)
for the relays. Q42, Q44 don't seem to have anything to do with the
fan either, so I'm wondering whats going on here. Thanks!
 
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