Peavey 5150 Problem Diagnosis - Bass Boost/Power Supply

[LOGANSTL]

I'm about to purchase a Peavey 5150 head from a fellow who says the only problem with it is that when it has been idle for about 15 or 20 minutes, there is a bass boost.

"Every once in a while it will get a very big bass tone to it as tho its feeding back, but when u hit it, it stops. From what i have been told from a
tech, it is something in the power supply ... The problem itself happens mostly when it is idleing for long periods of time IE 20-30 minutes"


Can anyone confirm that it is or is not the power supply? Or is it something bigger? And how might it cost to have fixed? Or might this be a simple fix I can do on my own?

Thank you lots
--jeff

[Amp Kat]

Big Bass as in the form of a huge hum. Normally a connection but not a guarantee it's in the power supply. Most likely the filter caps or a filter ca that has come unsoldered in the supply but Peavey glues those Nichcons down pretty good. It sounds like a loss of ground (bad connection) somewhere but I wouldn't put a direct link to the power supply.

[Mars Amp Repair]

Jeff,
I'm think it is the 5150 that has this issue; a few of these heads have a ground connection near the input jacks that is made purely by the screw that holds the circuit board in on that side.
Merely tightening this screw (I'd add a star washer under the screw) will resolve some weird issues like you're describing.
Now I'm a bit uncertain if that might have been a Crate Blue Voodoo...perhaps someone else can comment...

However, it most certainly sounds like a connection problem...

glen

[JerryP]

Does it have JJ power tubes?
Jerry

[Enzo]

Frankly I think it is a mistake to think in terms of 5150 rather than "amp." Too many people approach symptoms as if the particular model has this issue generically. Most problems are themselves generic, and not specificly something a particular model does a lot.

HAve we not just discussed this very amp either here or at the PV forum in the last week?

What exactly does bass boost mean here? The bottom end EQ goes up? Or does hum increase? The two would not likely respond to the same efforts.

If hitting the amp makes a difference, then do what you would do to ANY amp - tighten all the nuts on the jacks and controls, and tighten all the screws, especailly loose transformer m,ounting hdwr. If that is not it, then push on the ribbon cable headers.