Fender BXR 200

[FRANKJC]

Hi, my son has a Fender BXR 200 head, which is making a loud buzz noise when turned on. I got it to work once, no idea how but now all it will do is BUZZ.
It almost sounds like when you  unplug a guitar and touch the tip of the guitar cable but LOUD. Volume control makes no difference.
So far I have tried:
A different speaker cab.
Different speaker cable.
Different guitar, and cable.
Turned all the controls up and down.
Patch cable between effects send and return.
Plugged in a footswitch.
Next I am going to take it apart and clean the pots, and look for signs of anything damaged or burnt.
Anyone got any ideas? Thanks.

[Enzo]

Two likely things.  One is a blown output stage.  Producing DC on the output.  Look at the speaker cone.  When you turn it on, does it move one direction and stay there?  If it does that, you have DC on the speaker.  TURN IT OFF IMMEDIATELY as that can melt the speaker.  No music can come through if this is the case.

The other possibility is one of your main filter caps has failed or cracked free of its solder.  On the power amp circuit board are two cylinders sticking up near the middle.  They may need to be resoldered, or possibly one replaced.  If this is the case, you might hear the music trying to come through the hum.

[FRANKJC]

 Thanks for the information!
I don't turn the amp on for more than a split second, because of the noise. I'm thinking of checking for DC voltage at the speaker output with my multimeter.. I will also check  those caps that you mentioned, when I take it apart.
I do not know if any music comes through because i don't want to leave it on too long.
The fact that none of the controls seem to change anything leads me to believe that  it has nothing to do with the preamp section.
Thanks again for your response.

[FRANKJC]

Ok. Turn it on, the speaker sucks in and doesn't move. Preamp send to another amp works.  I do show DC voltage at the speaker cable.

[FRANKJC]

It was a bad solder joint at the filter cap. A dab of solder and a he's off playing "my name is mud".
Thanks for your help!