Fender BXR 400 Problems

[ariff]

Hey guys I have had a early 90's BXR 400 for sometime now. I just started having strange problems with it today. When the amp it turned on with nothing plugged in it makes a loud humming noise. If I plug my bass in I get real weak distorted output. I can also hear the transformer humming pretty loud as well. Could the transformer be causing this or not. Any idea what I should check to repair this amp. It is my backup so it is not used very much. I just hate to throw it out. Thanks..

PS here is a link to how it sounds.
http://www.unknownstuntman.com/bassman/

[Amp Kat]

Sounds like maybe a grounding problem are a cord problem. It is possible that maybe one of the output transistors quit working but if one shorted it would take that whole array down. If the positive or negative voltage to the output transistors is low that's a good sign that one or more has shorted. Since they are TO-3 package it's harder to check them as you really need to do a diode check and you also need to lift the emitter resistors on one side and check the resistors for opens. You can put your black meter lead on chassis and touch the top of the transistors and see if you get steady voltage all away across. Doesn't mean they are good but if the voltage is gone that's a sign they are probably not. If that amp has a send try the send out to another amp and if no hum you know it's in the output section. I think that schematic is on the Mr. Gearhead 3 CD.

[ariff]

I was able to fix the problem by repairing some broken\cold solder joints on the big caps on the PCB board. I also re-soldered any suspect joints and cleaned the PCB board for good measure. Thanks..