From robert@cs.stanford.edu Tue May 20 16:11:49 2008
Subject:Re: loud buzz in 122

> If any of y'all have any ideas I would love some input .... I've
> checked all solder points, and not noticed any of the tubes getting
> excessively hot ... even swapped out my 12AU7's and it's the same. What
> happens is that after warming up it get's a really loud buzz. I turn my
> preamp down and still have the buzz. I still have a signal coming
> through but the organ tone is really weak and very distorted. I'm
> guessing that because there is a buzz at all that it rules out the
> rectifier. Thanks for any input....

I would check the big filter caps in the power supply. If one of them
has failed it will let 60Hz through to the power tube plates, creating
a loud hum on top of the (distorted) signal just like you describe.

-- Robert