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Author Topic: Right Channel Hum After ~50 Hours Burn In [resolved]  (Read 3350 times)

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Offline Sixth.Gear

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Re: Right Channel Hum After ~50 Hours Burn In
« Reply #15 on: March 07, 2016, 03:30:25 PM »
The end of the red wire at A7 looks good. Where it is attached at the other end to the center pin of the pot looks it might a little light on solder in the photo. Or it could just be the angle of the shot. You might also tuck that red wire over a little closer to the pot and farther away from the red and black twisted pair that feeds A4 and A5.

I would also be inclined to reflow the lower center terminal of the front T strip, T3L, since that is a point of contact between signal ground and chassis ground. From the angle shown there is no solder filling the hole.

T3L had solder, but I reflowed and added solder, same with A7 wire on the pot. Moved the A7 wire higher and out of the way, but still a substantial hum. Hum still continues for about 5-10 seconds after power off.  :-\

Edit: Decided to run audio through it. At zero volume, audio is quite loud and mono on the right channel. Turning the volume up higher (approximately 50%), the audio switches to 95% left channel with right channel hum still present. Could something in the pot be bad?
« Last Edit: March 07, 2016, 03:38:13 PM by Sixth.Gear »

Online Doc B.

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Re: Right Channel Hum After ~50 Hours Burn In
« Reply #16 on: March 07, 2016, 04:26:57 PM »
Yes, unless you have wires crossed outside the pot it sounds like maybe it's damaged.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline Sixth.Gear

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Re: Right Channel Hum After ~50 Hours Burn In
« Reply #17 on: March 07, 2016, 04:53:26 PM »
Yes, unless you have wires crossed outside the pot it sounds like maybe it's damaged.

Thanks Doc. I just found another post regarding a pot going bad, and did resistance checks as you suggested from center terminal to outer. Lower (closer to backplate) gives good resistance values with pot movement, upper (farthest from backplate, and connected on the A7 wire) gives no-resistance values on my multimeter at 200k. I'm wondering if when I monkeyed with the A7 wire I damaged the pot somehow. Time to research replacement pots!

Thanks again for the help...its certainly been a huge learning experience and I'm definitely looking forward to the speedball once this is resolved.

Online Doc B.

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Re: Right Channel Hum After ~50 Hours Burn In
« Reply #18 on: March 07, 2016, 05:46:45 PM »
We can certainly supply another stock pot. To me the next worthwhile step up is an Alps Blue Velvet. It's great bang for the buck. My own experience is that you need to jump up to a quite a bit more expensive stepped attenuator to move past the Blue Velvet sonically.
Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline Sixth.Gear

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Re: Right Channel Hum After ~50 Hours Burn In
« Reply #19 on: March 15, 2016, 04:24:56 PM »
We can certainly supply another stock pot. To me the next worthwhile step up is an Alps Blue Velvet. It's great bang for the buck. My own experience is that you need to jump up to a quite a bit more expensive stepped attenuator to move past the Blue Velvet sonically.

Sorry for the delayed reply here. I ended up actually going with the Alps Blue Velvet, but it took way longer for it to get here than I anticipated (just about a week due to a game of UPS package football). Long story short, I believe that it was the pot that went bad as there's zero hum after upgrading. It's absolutely dead silent, no crackles, no pops, no hum, no hiss or any other noise. Perfect channel balance too.

Thank you so much again for the help Doc, I honestly can't thank you enough. Can't beat a product and support like this...absolutely worth every penny. That being said, I'll enjoy the crack for now and give a little bit before breaking out the speedball upgrade that's been on the shelf this whole time. Don't want to go and break it just yet ;)