Right Channel Hum

thoven0215 · 3595

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Offline thoven0215

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on: May 28, 2022, 03:30:34 AM
I just put in my shunt regulator upgrade, and there seems to be hum in the right channel. The voltages at OA and OB are both near 380 instead of 300-305, and KregB is at 10 instead of 2.5-5. What could be the issue?



Offline Paul Birkeland

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Reply #1 on: May 28, 2022, 03:44:51 AM
We definitely don't recommend listening to an amp that doesn't pass its voltage checks.

Do you have the +Reg to Breg jumpers installed?  If so, can you post some build photos?

Paul "PB" Birkeland

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Offline thoven0215

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Reply #2 on: May 28, 2022, 08:54:36 AM
I didn't at the time. I installed them and measured, and now OA is near 375, OB is 300-299, and Kreg is now floating between 1 and 2.



Offline Paul Birkeland

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Reply #3 on: May 28, 2022, 08:58:51 AM
There's a Kreg on the A side and a Kreg on the B side.  It's unlikely that they are both between 1-2V when one of your regulators appears to be working and the other isn't.  Can you post the actual voltages for Kreg A and Kreg B?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #4 on: May 28, 2022, 09:09:50 AM
Oops I omitted the B. Kreg A is at 5 Volts and Kreg B is at 1-2 Volts.



Offline Paul Birkeland

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Reply #5 on: May 28, 2022, 10:26:43 AM
There's a 50/50 chance that if you replace the 431 regulator on the low side, everything will snap back into place and work properly. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #6 on: May 28, 2022, 10:45:12 AM
I do not have an extra regulator to replace it. Should I contact the replacement parts email?



Offline Paul Birkeland

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Reply #7 on: May 28, 2022, 11:14:48 AM
Yes.

Paul "PB" Birkeland

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Offline thoven0215

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Reply #8 on: June 06, 2022, 12:45:02 PM
I replaced the regulator, but the problem still persists. All the values still measure the same as I last stated. What do I do next?



Offline Paul Birkeland

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Reply #9 on: June 06, 2022, 12:48:21 PM
What voltage do you see a KregB?  If it's still well below 2.5V, I'd want to see the bottom of the C4S/Regulator PC board.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #10 on: June 16, 2022, 09:31:49 AM
Sorry for the late reply, I had a nasty case of the flu. I rechecked the back of the board and noticed I did solder a wire to the wrong spot. I fixed it and here are some pictures of the back and front. Is there anything I've missed?



Offline Paul Birkeland

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Reply #11 on: June 16, 2022, 10:19:54 AM
I would give it another shot.  Do you remember which connection wasn't where it was supposed to be?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline thoven0215

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Reply #12 on: July 03, 2022, 11:57:14 AM
Yes, I put it in the hole above OB (when you orient the letters correctly). I tried soldering everything back in and testing the voltages, but it started smoking. I unplugged and saw that it seemed to be the resistor next to the capacitor on the B side of the board that was smoking. It appears cracked now. What should I do?



Offline thoven0215

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Reply #13 on: July 03, 2022, 11:58:58 AM
I can't seem to post the images, so I will keep trying until I figure it out



Offline thoven0215

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Reply #14 on: July 03, 2022, 12:05:53 PM
Pics