Blues junior III tube socket

[mikeskory]

The noise came back. Curiously not as loud as it was prior to all the current work. It's more predictable now. Pulling V3 PI stops the noise. Pulling V1/V2 will not stop it. I cut the R48 like nick suggested. It's like clock work. When I unhook R48, it the noise fades out in a few seconds. When hook R48 back up the noise starts right in. Clipping in a 22mf over clipping in a fresh 22mf onto C26,C27 or C28 make no change.

[nickb]

The noise came back. Curiously not as loud as it was prior to all the current work. It's more predictable now. Pulling V3 PI stops the noise. Pulling V1/V2 will not stop it. I cut the R48 like nick suggested. It's like clock work. When I unhook R48, it the noise fades out in a few seconds. When hook R48 back up the noise starts right in. Clipping in a 22mf over clipping in a fresh 22mf onto C26,C27 or C28 make no change.

I think the B+ supply test rules out the bias supply as the issue. Next most likely suspects are the coupling caps into the EL84 grids i.e. C15 and C16. Also the plate resistors R28, R30 and R29 are candidates. Not my first choice but as you found you had to remove both EL84 to make the noise stop it means more than one component has died. Sadly you'll have to get to the back of the main PCB to do this and lift one end of each cap to test.