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Re: One step at a time.

Thanks for all the help, Peter. I shorted the inputs and the hum was still present, if not a bit louder. When I disconnected the coupling caps, I do still have hum, but it's barely audible and only in one channel. I noticed that it follows one of the output tubes if i switch in from left to right. Possibly a bad tube? Not a huge concern as far as hum, but if it could have other repurcussions WRT the functioning of the amp, I'll of course replace it.

Now on to look closely at the amp stage. Any pointers at this step?

Also, is it normal for B+ to drop from about 430V to ~390 or so once tubes heat up? I also notice that the B+ drops really quick when power is cut, down to ~10V within a few minutes. I seem to remember it holding a steady high voltage for much, much longer than that previously. Victor got me thinking that a tube might be shorting out internally when hot.

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