Enzo,

Thanks for the 411.  I don't have a scope but I have a fairly good VOM and DVM to start checking voltages.  I won't get to it for a few days but I will post what I find....

AAC

Solid state.  It hums whether my bass plugged in or not.  The hum doesn't get louder or softer or change character when I move any one of the controls.  Outlets are grounded.  This is more than a slight hum.  My Crate BX-15 has a slight breath, the B80XL has severe respiratory illness...    

Quote from: Jack1962 on October 07, 2008, 04:24:26 AM
A lttle more info is needed bro, is this a solid state amp or tube , does it hum with the cord not pluged in , is it a loud hum or does the hum change pitch, is your wall outlet grounded? some amps have a slight hum to them this is called the amps breath.

                                           Rock On

This is my first post on this forum so please be gentle 

I was given a Crate B80XL bass amp (80W/1-15 combo).  It works quite well but it hums whether my passive Peavey Grind NTB-5 is plugged in or not.  The guy that gave it to me said it 'always' hummed.

I haven't gone beyond preliminary troubleshooting but so far (I think) I have determined the hum is coming from the power amp section as the hum doesn't get louder or softer or change character when I move any one of the controls.  I hope I am correct in my presumption(s) so far.  Does anyone here know where I can get a schematic for this amp?  Or does anybody have any experience with this amp (or its relatives) in curing the hum problem?

Otherwise, when I finally get to open it up (not soon - my work area is being painted), I will:

1) Clean every control, switch, jack, etc. I can access.
2) Check all of the grounds to make sure there are no cold solder joints
3) Test all of the power supply caps, diodes, etc....

Any other thoughts would be helpful!

AAC