"Mark" wrote in message
ups.com...
This was a dog I would not wish on anyone...

Q511 was shorted on the power supply board. If you replace it with
another small transistor it will overheat and fail again. I replaced
it with a TO-220 3055 type NPN power transistor with a small heat sink
on the tab....keeps it cool...

Also unit still acted erratically...

check the +5 volt regulator on the CPU board on the front panel...

Replaced it and everything worked EXCEPT the remote control did not
work...

this is a BS design, the 3 terminal 5 volt regulator has it's ground
lead FLOATED up by 0.7 Volts with a diode....so the actual supply
voltage will be 5.7 Volts.



That is a common practice, and quite valid. The forward voltage drop across
the diode is pretty consistent, and doesn't impact hugely on the overall
stability of the regulator. I have seen it done where manufacturers have had
a further series diode, or R-C decoupling network in the 5v supply feed to a
board or micro, where the additional drop across these items, would cause
the 5v to drop below the point where the micro can reliably operate ...

With 5 volts on the supply it kinda works but not reliably and the
remote didn't work.....
I upped the voltage to 5.7 Volt supply in place and it worked fine...

.... as you found.

Arfa