T/R startup voltage and hum

[NoobGuy]

Okay, I disconnected the existing grounds at the RCA side, and ran a separate wire from both RCA tags to the ground at the pot. No change.

If it is indeed the 220uF caps would the hum increase with volume as I'm experiencing?

[Doc B.]

It might be that a pot replacement is in order. I can't say if that will solve the issue, but we can send out a replacement if you want to give that a try. Beyond that it is a little difficult to suggest what to try, because of the changes made from the stock components. Reflowing all the solder joints from the inputs to the tube sockets might help too.

[NoobGuy]

Thanks Doc .

I've still got the original pot, will put that in and see if it helps. Maybe I got the Alps too hot at some point.

[NoobGuy]

FIXED! 

So after taking out the Alps pot, putting in the stock one, checking and-rechecking every single solder, I still had the hum. Aaaargh! I was about ready to toss the whole thing out the window.

And then I realised how silly I had been. When I had the panel painted, I sanded off a patch so there would be metal contact for the earth lug. But I neglected to do this for the pot shaft. I added a little wire from the shaft to ground, and the hum is all but gone. It's still there in a small amount at very high pot position, but this is well beyond normal / safe listening levels.

Happy ears now! Thanks for all the help guys.

[Doc B.]

Very good catch, not something that would have come to me unless I had the amp in my hands.