wrote in message
ups.com...
I have one of the early sunfire subs that has had a hum problem for
some time. It seems to be in the power supply of the sub. I have the
same hum when it is not connected to the stereo and doesn't go away
when I change outlets (still unconnected) so I don't think it is a
ground loop problem.

I sm looking for some help on troubleshooting this. Does any one have
a schematic?

Thanks.

Dennis

Be careful. I suspect it's a switchmode supply.
Switchers have a bad reputation for repairs. Many or most of the faults are
impossible to intuitively diagnose. One yahoo group I subscribe to
specializes in repair of Tek scopes. The general feeling is that in many
cases, you won't find the problem unless you have the ability to swap a lot
of parts, and have a good unit for comparison.

Also beware of the voltage. Those things tend to hold a charge for a while.
Because of the complexity, you may miss a cap that should be discharged.
When discharging, do not short the cap, because that can destroy it. Bleed
it down with a resistor.