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.

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...

Replaced the 5 volt regulator with a TO-220 also and replaced the
shorted diode that lifts the ground lead. You need to get 5.7 Volts
on the CPU supply PWB for this beast to work well...

You don't have to remove the CPU card from the front panel which is a
bear to do...
the 3 terminal regulator is 3 leads that you can get to from the back
of the PWB, it is just below where the leads come up from the power
supply...

Hope this helps

Mark

"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