I have an SE84A with a hum problem. Is this where I ought to ask it?

Thanks!

Awesome. My amp is second hand -- I bought it from the original owner.

I am a relatively experienced amp owner (i.e. I've built a few tube amps from scratch, though its been a few years). I adore my SE84A, but it's developed an intermittent hum. The hum comes from both speakers and comes and goes. It's definitely something out of the ordinary (it's louder than the base hum). Interestingly, flipping the bias switch a couple of times seems to usually makes it stop temporarily. I haven't been able to determine if its still there if I pull the input tube.

Any ideas of what to check? I have a multimeter and can test.

Okay so I did some more testing: when the hum is going on, I turned off the amp and removed the input tube. The hum was unchanged. Then I removed both output tubes. No hum. Then I replaced the output tubes one at a time. With either tube, in either channel, there was hum on that channel (i.e. when they were both in, there was hum on both channels).

This means its not input tube or switch right? I suppose its possible that both output tubes are bad, but that seems rather unlikely?

You can ride the gain, i.e. adjust both devices to see what sounds best. It could be recording dependent at times.

A fresh tube set would bring the unit to life again. You have solved the hum problem.