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.
Right channel noisy. Help troubleshooting
- Thread starter denti alligator
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denti alligator
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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?
You replace the remaining tube sockets and potentially any terminal strips that could have been affected by the green goo.
denti alligator
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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.
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
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Can you tell me how to do that?Paul Birkeland said:
You can wrap a piece of bare wire around the 249K resistor.
denti alligator
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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 said:
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
New member
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 said:
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
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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?
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?
Yes, connecting 4 and 5 is the same as connecting the resistor leads.
denti alligator
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Alright, I’ll try it one more time to be sure.Paul Birkeland said:
denti alligator
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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?
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?
If the noise is there with terminals 4 and 5 connected, that indicates the PC boards are fine and that you should not remove the shunt regulator.
I would swap 2A3s just to rule out the most obvious possibility. You can leave the jumper in for now.
I would swap 2A3s just to rule out the most obvious possibility. You can leave the jumper in for now.
denti alligator
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OK, 2A3s swopped. Same noise. Same channel. It’s immediate now when I turn it on.
Now try it with no 2A3 at all.
denti alligator
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No noise.Paul Birkeland said:
Is there any green staining around the hum pot?
Do the DC voltages wander around when the noise creeps in?
Do the DC voltages wander around when the noise creeps in?
