Right channel noisy. Help troubleshooting

[denti alligator]

I’m replacing the parts Paul recommended to replace on the right side. As I’m doing so I’m seeing something that seems to me the obvious source of that green stuff: the 0.15ohm 3 resistors on the socket. They have a primarily green color, are right there where the green stuff was found, and I’m seeing that tiny bits of the outer green part of the resistors has chipped off. It’s the same green color that was there. Could I be that I put too much heat on those and the outer part (what’s it made of) “melted” down onto the socket?

Could these resistors be damaged in some way? They are not among the parts you told me to replace.

I’ll report back later, once I’ve switched everything out.

 

[denti alligator]

OK, everything has been replaced. I flipped it on and it was noisy. Damn. But that only lasted about 10-15 seconds. Like it needed to clear its throat first. Mind you, this is only happening on the right channel, not the left, so this isn’t the usual slight sound of turning the amp on. But now it’s been quiet for about 5 minutes with only very, very, very tiny little pops every now and then. Fingers crossed. This might be the end.

 

[denti alligator]

Right, spoke too soon. It’s definitely quieter. But those pops and scratchy sounds still come in every now and then. I’m keeping track of it.

By the way, with the balance turned all the way to the left channel I still hear the noise in the right channel. Not sure that helps identify anything.

In setting the hum pot I noticed that the right channel also has more hum than the left. And if I put my ear up to the mid range speaker I can hear a constant low-level scratchiness. So it’s still there, all the time, but it only gets loud enough to hear from listening distance about once every minute or so, then it quiets down. Certainly better than it was before, but not totally gone.

What other parts might I try replacing?

(Note that I didn’t replace the wiring, just the parts Paul listed above.)

 

[Paul Birkeland]

I’m seeing something that seems to me the obvious source of that green stuff: the 0.15ohm 3 resistors on the socket.

What about the hundreds and hundreds of other 0.15 ohm resistors in everyone else's Stereomour kits?  How about the tens of thousands of these resistors that have been sold over the last decade and installed in consumer electronics? A little bit of critical thinking in situations like this can go a long way.

 

[denti alligator]

Look, no need to get snarky. I’ve told you over and over that I have not used anything besides the products recommended on this forum and I’m trying to figure out the source. The same critical thinking would have me believe that whatever was there on the socket should be elsewhere, but I found no evidence of it. Not in any of the six or so other Bottlehead kits I’ve built. So I’m desperately trying to think where it may have come from. Maybe I overheated those resistors or something, I don’t know. It seems more likely than that this stuff came from the solder or iron or whatever. I was asking “might it be” the source since there is something green there with missing green parts. Doesn’t seem that outlandish. And you could have simply answered “no, that’s not possible” instead of insulting me.

Anyway, if the noise is still there, what am to do now?

 

[Paul Birkeland]

Next you'd want to put a clip lead back across the 249K resistor from 2A3 grid to ground on the noisy channel to see if the noise is still present.  When you performed this experiment previously, the noise was unchanged, and it would help to know if that's still the case or if this eliminates the noise.

 

[denti alligator]

OK, I clipped a lead across that resistor as before and the noise is still there. Note, however, that it is significantly less constant and loud.

 

[Paul Birkeland]

Now swap the 2A3s to see if the nature of the noise changes.

Also if you have to press your ears up against your speakers to hear what you're hearing, that would suggest that the amp is quiet enough.

 

[denti alligator]

Yes, same noise with tubes swapped. I can hear the noise from 10 feet away. It is quieter, though, and less frequent. But then again, when I left it on for a week I had a day or two when it was similarly less constant and less loud. My comment about putting my ear up to the speaker was just to confirm that the low-level noise is indeed constant, unlike in the left channel, which is dead silent.

I’m happy to replace the remaining wiring and resistors in the right channel output stage, if these might be responsible. What about the other tube socket? Or, what parts could I swap with the other channel to see if the noise moves?

 

[denti alligator]

Unless you think it’s a waste of time, I will swap these parts from one channel to the other to see if the noise moves: .15ohm resistors on 4-pin socket, .1uf. Capacitor (4U to 7U), 220ohm resistor (A3 to 4U).

Should I replace the wiring near the R channel 4-pin socket?

 

[Thermioniclife]

How about you swap output transformers.

 

[denti alligator]

How about you swap output transformers.

I may do that just to rule them out. I mean, it has to be coming from somewhere, and it’s not in the left channel. Having replaced most of the output stage of the right channel I might as well keep going.

 

[2wo]

It does sound like you have come to the point of swapping transformer or other major components. If nothing else it gives you a chance to scrutinize each wire for something like a break under the insulation or something insidious, hold it in your hand and able to look from all angles.

And sometimes just taking it apart and putting it back together can make it magically start to work; gotta believe in magic...John

 

[Paul Joppa]

This is a tough one! I've been following the thread, but I'm not as familiar with the layout of the 2.0 so I've not been posting.

I can't say I remember every trial that's been made, but it seems the noise is determined to be in the output stage or power supply. It occurs to me that the power supply is "pseudo dual mono," that is there are two stages of RC filter for each tube (130 ohm/100uF). You should be able to swap the power supply outputs between channels to test them.

I think you've already tried swapping speakers, in case it's a fault in one of them or the cables or connections. But I may be mis-remembering, so worth a try if you haven't.

 

[denti alligator]

This is a tough one! I've been following the thread, but I'm not as familiar with the layout of the 2.0 so I've not been posting.

I can't say I remember every trial that's been made, but it seems the noise is determined to be in the output stage or power supply. It occurs to me that the power supply is "pseudo dual mono," that is there are two stages of RC filter for each tube (130 ohm/100uF). You should be able to swap the power supply outputs between channels to test them.

I think you've already tried swapping speakers, in case it's a fault in one of them or the cables or connections. But I may be mis-remembering, so worth a try if you haven't.

Thanks, Paul. I have tried swapping speakers. Even tried different speakers to be doubly sure.

I’m not following you on the RC filter: how would I swap the power supply outputs between channels?

 

[denti alligator]

Changed the misleading subject heading of this thread, since the left channel issue was resolved early on.

Yesterday I swapped out the 0.15ohm 3W resistors. Noise still in R channel.

Today I'm going to swap the 0.1uf 630V cap on 4U/7U and 14U/17U and the 220ohm resistor on A3/4U and D3/17U.

After that I guess I'll swap the transformers.

What else is in the path that I could check?

 

[Paul Joppa]

Thanks, Paul. I have tried swapping speakers. Even tried different speakers to be doubly sure.

I’m not following you on the RC filter: how would I swap the power supply outputs between channels?

I'll get back to you, but it will take me a while since I don't know the v.2.0 layout well.

 

[Doc B]

There is a blue wire coming off each plate choke that eventually connects to pin 2 of one of the 2A3s. One side side it is attached at 1L. On the other side it is attached at 20L. Just swap the blue wires connected at those terminals. I'm guessing you may need jumpers/clip leads. Be very careful not to short the jumper connections to anything.

 

[denti alligator]

Thanks, Dan! Too late, though. I already removed both transformers. Oh well, fun times. I'm really, really hoping the noise travels channels, otherwise I feel like we've hit a dead end. Fingers crossed.

 

[Doc B]

Might as well do both. Swapping output transformers will tell you if the output transformer or its connections are making noise. Swapping the final power supply nodes will tell you if the noise is coming from the power supply filter components that are unique to a channel. I would lean towards the power supply final node being more a likely culprit than the OT.