Problem with Peavey Mark3 400BH

[Bigroo76]

This amp will allow me to play my bass thru my cab but it never stops humming. I cannot seem to get rid of the hum. I turn it on, hum. I play my bass and adjust gains, still hums. What am I doing wrong? I have no money to have my SVT amp retubed right now and use this Peavey as a back up. I am ready to go out and shoot it up!! Please help.

[Enzo]

If it hums when ALL the controls are at zero, then the power amp part is humming.

Most likely thing is cracked solder on one of the main filter caps. Or one of those caps could have failed. Certainly other things are possible, but those are most likely.

[Bigroo76]

even while i am playing thru it hums. Should it really hum that loud. Its pretty obnoxious humming.. Also, what is a filter cap?

[Bigroo76]

screw it.. I went out just now and bought a GK backline 600 4ohm solid state amp for my 8ohm 4x10 cab. Will this set up work. Will I blow my amp and speaker cab. How does this ohm thing work. What is the conversion of ohms? Also I would like to add my Sans Amp DI pedal for a more clean punch. Will I blow up my gear if I connect a 4ohm amp to a 8ohm 4x10 cab? Let me know so I dont screw up. I am ignorant when it comes to this type of thing...Thanks

[Jazz P Bass]

Peavey 400BH

The Peavey 400BH is a time tested output section.
It is basic, simple & it works.
If your amp is humming, something is amiss.
If it is a power rail issue, it may be the filter capacitors.
The filter caps Enzo referred to are a part of the power supply.
The AC voltage comes in from the wall outlet into a transformer which converts it down to 45 Volts. While still being an AC voltage, it is unuseable in this form for the amplifier.
The amplifier works off of DC voltage. That is the next set of parts. (4) diodes convert the AC voltage to a workable + 52 & - 52 Vdc.
This is a ratty looking Vdc. That is the job of the filter capacitors.
They smooth out the ripple in the Vdc.
If one (or both) of the caps is bad or not soldered securely, the rattyness gets through.
Hence, the hum.
Testing the +52 & -52Vdc power rails can verify if this is the fault.