Aleph 3 diy problem with one channel - diyAudio
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Old Today, 07:13 AM   #1
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Join Date: Jan 2015
Location: Bay Area, CA
Default Aleph 3 diy problem with one channel

I've been messing around with this long enough and I'm ready to seek help... That being said: I've built a Aleph 3 and I'm having a terrible time figuring out a problem I'm having with one channel. The unit starts up and I dialed in bias and offset and just when I plugged in my iPhone to check it, it went pop. My phone that is. The 3.5mm jack blew up on my phone.

I checked and found I had offset voltage on the input from one channel reaching .6volts and the other side was at 0. I blew a capacitor on the side with the voltage. After replacing it I checked input offset and found it had returned to 0 on both sides. I put the project down a couple days and thought it over.

Today I returned to it and I measured voltage at the input and found one channel to have 0, like it should, and the other to have -27volts! The one with the voltage issue is the one that has performed correctly all this time without any failure. I measured across the voltage rails and I have 55 volts, but 53 from the negative and 2 from the positive to chassis ground. I also have -27volts on the "ground" coming off my supply capacitor bank.

All my voltage reading are off on this channel and I have no idea where to start. I disconnected the power supply from the amplifier board and it performed as it should, + and -27 volts. As far as I can tell, the negative voltage is feeding back through the entire system through the ground and I'm not sure why or why the negative voltage is so high. One last piece of evidence is I found a blown diode on this channel as well, but after replacing it nothing changed.

Any ideas on where to start or what to check would be extremely helpful. Thank you.
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Old Today, 09:06 AM   #2
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For starters, as always, post pics. Ideally post a schematic of the actual build showing wiring and with voltage measurements annotated.

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