Audio Systems: Pioneer deh-p7800mp, pioneer deh, bench time

Question
A a couple amps were plugged into my 7800 MP and a week before
competition, we pulled one of them and plugged another one into the unit for
the front component set.  All of a sudden, I got this shrieking noise
like I had a bad ground.  Figured it might be the amp, unplugged it and
put the old amp back on it.  Same thing.  Went through all the grounds,
made sure they were sturdy.  Tried adding another ground to the deck
itself, but to no avail.  I was wondering what the problem might be.  I am
thinking that the RCA pre-outs are shot.  Not sure if just the
pre-outs gave out on me, or whether something internal may have popped inside
the unit itself.  It still plays, but I have to deal with the noise if
any amps are plugged into it.  I was wondering if there was any way
around sending it back to Pioneer for service.


Answer
There is most likely a bad cap in the pre-amp circuit.  This unit will require bench time to locate the failing component(s).  Any local service shop shuld be able to help you.  If the unit still under warranty? If not, call around to check service cost.  Sometimes it is cheaper to replace the unit.
Dan