Right channel noisy. Help troubleshooting

[Paul Birkeland]

I have no idea what causes the discoloration I sometimes get on the bare metal.  When I've done this, I always do it with no detergent and the silver aluminum plate will often take on mild gold hues here and there. 

[denti alligator]

OK, I ran it through the dishwasher today. That cleaned it up nice! The green discoloration on the left socket is now gone. Resistance and voltage check out fine. Same noise is present in the right channel. Where do we go from here?

[Paul Birkeland]

You replace the remaining tube sockets and potentially any terminal strips that could have been affected by the green goo.

[denti alligator]

I don’t know what that was and the last time I saw it it was on the left socket (no noise in left channel). Is there any way to isolate the source of the noise more precisely? Seems like a lot of work for something that may not be the cause.

[Paul Birkeland]

You can ground the grid of the 2A3 on the noisy channel to see if that makes the noise go away.  That is how I isolated the noise on the output stage when I had your amp on the bench.

[denti alligator]

You can ground the grid of the 2A3 on the noisy channel to see if that makes the noise go away.  That is how I isolated the noise on the output stage when I had your amp on the bench.

Can you tell me how to do that?

[Paul Birkeland]

You can wrap a piece of bare wire around the 249K resistor.

[denti alligator]

You can wrap a piece of bare wire around the 249K resistor.

Can you be a little more detailed. What kind of wire? Anything? How much? Wrap around what part? The body? How many times? (Sorry for all the questions)

[Paul Birkeland]

Since you are trying to create a short, you are connecting one end of the 249K resistor to the other end of the 249K resistor.  A clip lead would work fine.

[denti alligator]

Since you are trying to create a short, you are connecting one end of the 249K resistor to the other end of the 249K resistor.  A clip lead would work fine.

Got it, thanks. I’ll try this a bit later. If I still hear the noise, what does this mean? If I don’t, what does it mean?

[Paul Birkeland]

It splits the circuit in half.  Noise present means it's related to the 2A3 output stage.  No noise means it's back around the 9 pin socket area.

[denti alligator]

Well, it was not easy to attach a wire there. The lead on one side was practically non-existent. But I think I got it and the noise still persists. (Though I guess it’s possible I didn’t attach the wire well enough. Can I just connect terminals 4 and 5 instead of trying to get at the resistor leads?)

If I have to systemically replace the parts, I’d rather go one at a time. What are the terminals, parts that this narrows it down to?

[Paul Birkeland]

Yes, connecting 4 and 5 is the same as connecting the resistor leads.

[denti alligator]

Yes, connecting 4 and 5 is the same as connecting the resistor leads.

Alright, I’ll try it one more time to be sure.

[denti alligator]

This time very securely connected 4 and 5. Noise immediately audible upon turning on the amp.

So, where should I start? Terminals 1-5 and 21-25? Could it be one of the PC boards? Should I take out the shunt regulator to eliminate that as a possible source?