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October 05, 2022, 09:44:30 PM

Author Topic: Right Channel Hum  (Read 743 times)

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Offline thoven0215

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Right Channel Hum
« 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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Re: Right Channel Hum
« 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

Bottlehead Grunt & The Repro Man

Offline thoven0215

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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« Reply #7 on: May 28, 2022, 11:14:48 AM »
Yes.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline thoven0215

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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« 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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Re: Right Channel Hum
« Reply #14 on: July 03, 2022, 12:05:53 PM »
Pics