Peavey Series 400 Bass head - needs a doc in Illinois

rolandm · #1 11-03-2010, 12:13 PM

Sorry ... I don't know why Mark IV was stuck in my head. It's a Series 400 bass head and I don't know how to edit the subject. -

Prior to purchasing my Behringer, my 1978 Peavey Series 400 was my head of choice. It developed a squeal however, and being as I was looking to upgrade to something lighter for gigs, I never did much with it. However, now I am looking into fixing it, and not too many people around here work on these.

So, A) anyone in or close to the central Illinois area still working on these dinosaurs? and B) what could typically cause a high-pitched squeal out of the amp during playing or rested periods, whether running series, parallel (not-channel specific, in other words).

Any ideas are appreciated. Thanks!

BassmanPaul · #2 11-03-2010, 12:55 PM

A) Can't help.
b) Parasitic oscillations. Most likely a failed decoupling cap on the power rails.

rolandm · #3 11-03-2010, 01:00 PM

Is this something that I should try detecting on my own if I can't find someone local enough to fix it?

rolandm · #4 11-03-2010, 01:12 PM

Never mind. I searched the dealer locator on the Peavey website and found that a local shop has picked up the Peavey repairs from the old one. Must have been fairly recent, because when this went down, it was a 3-hour trip to get it fixed.

Thanks for your help!

KramerBassFan · #5 11-03-2010, 02:47 PM

Does it have the same problem being run on different outlets?

I've encountered the same problems by running large amps on 18 gauge cords.... in addition to a large fan.

Needless to say... i got unpleasant sounds, even when the "volume" and input gain were all the way down.

Just something to try.

But more likely, one of the filter capacitors has gone bad.

Its common on old amps, and pretty easy to fix.... if you are Electrically inclined and good with a soldering gun.

Jim C · #6 11-03-2010, 02:49 PM

Call the Smithonian; I didn't think these amps ever stopped working!
Question is: will it be worth the repair cost to keep it running

crentest · #7 11-03-2010, 02:58 PM

i would think the repair cost should be fairly low as i don't think the amp is all that complicated to work on.
p.s. mine still works great!

rolandm · #8 11-03-2010, 03:12 PM

Well, I figure if it's not going to run me an arm and a leg, I'll get it fixed, and re-cover it and the bass cabinet. Anyone know if Peavey might have replacement parts like top vents and corners?