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

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.

if you have cable or satelite tv hooked up in the room, I would disconnect
that connection from the wall and see if your hum doesnt disappear. i bet
it does. most common cause of ground loop hum is the cable tv. if it does
disappear email me and i will give you the fix.
brooks
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

Brooks,

I turned the cable box off & disconnected the coax cable running to it.
Still hums. I didn't want to unplug the cable box power because it is
a DVR & I think I loose the recordings when it is unplugged.

Dennis

wrote in message
oups.com...
Brooks,

I turned the cable box off & disconnected the coax cable running to it.
Still hums. I didn't want to unplug the cable box power because it is
a DVR & I think I loose the recordings when it is unplugged.

Dennis


That is one of the vintage Bob Carver/Sunfire curses. In many locations the
last resort is to lift the ground which is not a good idea AFAIK. I had a
couple of his products that seemed to be at first a good value but then crap
like that happened and I dumped them all. Sell it and get something decent.

Sorry about the bad news.

Margaret

wrote in message
...

I didn't want to unplug the cable box power because it is
a DVR & I think I loose the recordings when it is unplugged.

With statements like this, you're obviously to stupid to learn anything
here.

Get lost.