Right Channel Hum

[thoven0215]

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?

[Paul Birkeland]

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?

[thoven0215]

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.

[Paul Birkeland]

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?

[thoven0215]

Oops I omitted the B. Kreg A is at 5 Volts and Kreg B is at 1-2 Volts.

[Paul Birkeland]

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. 

[thoven0215]

I do not have an extra regulator to replace it. Should I contact the replacement parts email?

[Paul Birkeland]

Yes.

[thoven0215]

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?

[Paul Birkeland]

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.

[thoven0215]

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?

[Paul Birkeland]

I would give it another shot.  Do you remember which connection wasn't where it was supposed to be?

[thoven0215]

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?

[thoven0215]

I can't seem to post the images, so I will keep trying until I figure it out

[thoven0215]

Pics