Right channel noisy. Help troubleshooting

[denti alligator]

Great, thanks. I’ve remounted the transformers. I’ll wire them standard first and check, then try swapping the blue wire.

 

[denti alligator]

We have the source of the noise!! It’s the transformer! I swapped them L/R and indeed the noise went from the R channel to the L channel. Phew!

Doc, can I get a replacement from you guys? I am happy to pay for it.

 

[Doc B]

Best bet is to do this thru the replacementparts@bottlehead.com email. We can certainly replace the noisy transformer but I'm not sure what the stock situation is on that part as I sit here. Transformers have been one of our biggest hangups supply-wise and Eileen can check inventory status and let you know via that email.

 

[denti alligator]

I’m assuming I need the plate chokes, too? Do they come as a pair?

 

[Doc B]

I don't see any reason to replace the plate choke if the output transformer is the part that the noise followed.

 

[denti alligator]

Sorry, my bad. I replaced swopped both parts. I just assumed they went together. So actually, I don’t know for sure if it’s the transformer or plate choke that is causing the noise. Is there a way to tell without stopping one part back?

 

[Doc B]

Not that I can think of. Always change one thing at a time.

 

[denti alligator]

Alright, back to the bench!

 

[Thermioniclife]

Perhaps just disconnect the choke inputs and outputs and temporarily extend the wires to put the chokes back to their original sides. This is not foolproof but may be telling.
Scientific method states only one variable change at a time.

 

[Paul Joppa]

Not that I can think of. Always change one thing at a time.

Swapping the blue wires will swap plate chokes and power supply filters - but the output transformer exchange you just did says it isn't the power supply, so that's an OK way to test the chokes.

 

[denti alligator]

That was a PITA, but it’s done and a good thing, too. So it’s NOT the transformer but the plate choke that is causing the noise. Swapping chokes moved the noise back to the right channel. Any idea what might have caused this part to fail?

 

[triode]

Following this thread with great interest
My Stereomour (I) also making noise as described here; also only right channel
Maybe I'll try to swap the B+ connection to plate choke (red wire in my case since its configure for 45 tube)
 

 

[Doc B]

I think you will probably be disappointed. This case is way an outlier. We have not ever had another noisy plate choke that I can recall. So it seems unlikely that lightning will strike twice in the same spot. Best to check the more likely culprits like bad solder joints first. Once the more likely things like tubes, solder joints, pin contacts, resistors and capacitors have been eliminated you could move on to more unlikely causes.

 

[triode]

Maybe Doc,
But this noise problem had going for a while and I have tried and eliminate the usual suspect : tubes, speaker, reflow soldier joint etc.
Since this check only involve swapping 2 wires, I might try it anyway.

I'll report back

Thanks

 

[triode]

Hi

I swapped the choke by swapping the blue wires connected to 4pin socket from left to right.
The result : noise is moved from right to left. I think the choke has some problem.

I guess I will need to order replacement

 

[Paul Birkeland]

If you swap just the blue wires, you are changing the current loop for the output stage to include the other half of the pseudo dual mono power supply. 

 

[triode]

Thanks Paul

Yes, by swapping the blue wires, this swapped the choke, the 1.2k resistor, and the final filter Caps
Maybe I will try also to swap the choke's red wires and if noise still in the same channel, then definitely its the choke 

 

[triode]

Hi all,

Update : I swapped the choke red wires and it still in the same channel/choke. So its not the resistor and filter caps in the PSU. I guess I have a bad choke?

Thanks guys

 

[denti alligator]

Received my plate choke replacement today (thanks, Eileen!), swapped out the defective one and the amp, at first, had no sound in the right channel. I checked voltages, which were slightly low around 6, 21, 22 (51.7V compared to 56.something on the other side), but all else well, so I plugged it back in and …

… it works! And it sounds great! And there is no more noise!!

Thanks so much for helping me get to the bottom of this!

 

[triode]

That's great news.

I'm ordering my replacement now. Hope same result as yours

Thanks for this thread, I would have not expected that the choke are the source of the noise