"Bob F" wrote in message
...
Leonard Caillouet wrote:
"Bob F" wrote in message
...
This sub hums a lot when first turned on, and once in a while starts
popping very loudly shortly thereafter, at which point I have to
turn it off. It seems "unstable" at turn on, making funny noises
before the popping. The rest of the time, the hum fades down to
barely noticable, and everything is OK other than the low hum.

I talked to the manufacturer, who said this old design had this
problem, and the only solution was to send the amp to them for
repair/replacement for $285. They describe this amp as a "beer-can"
amp or something like that, IIRC. The power amp part is in an
aluminum can of some sort. If anyone has dealt with this unit and this
problem, I would love to
receive hints for repair.

My first thought is just to replace the large filter caps and see if
this helps.



Look for the obvious, like a separated surround. IIRC this may have
been one of the units with the accelerometer in the woofer and a
servo circuit. Separated surrounds would cause this kind of symptom
on them.

The surround look perfect. Pushing in on the cone, I notice it seems to
have a very stiff suspension.




Lots of their amps are made with a heat sink wrapped around most of the amp
circuit. They are a PITA to service. With that kind of symptom, I'd be
looking for a cap or a leaky FET, possibly an op amp going bad.

Leonard