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gasjack 18th February 2004 08:51 PM

Loud hum problem

I have built a six-channel amp using the 3886 chips. I built it using PCBs from

Untill yesterday it worked just fine. However, there was a slight hum on the channels closest to the power supply, so I had the case open and was trying to rearrange the wires to minimize the humming. Suddenly a spark came from one of the PCBs, and it started humming much louder.

I have tried resoldering all the grounding joints but to no avail. I am not sure, but I think the spark might have come from one of the joints where the caps are soldered to the PCB. Could it be a faulty cap perhaps? (the amp still works despite the hum though)

Any suggestions?


AGGEMAM 18th February 2004 08:59 PM

I think you're right in that it being a faulty cap. Try taking them out and test them.

gasjack 18th February 2004 09:33 PM


Originally posted by AGGEMAM
I think you're right in that it being a faulty cap. Try taking them out and test them.
Even though the amps still plays?

Well I tried testing the caps using this technique but they seemed to be OK.

If anyone knows of another way to test them please let me know.

gasjack 18th February 2004 10:55 PM

I tried this method too. And the filter caps seem to be alright.
It should be noted, that the amp plays fine except for the loud hum (at least it did before i desoldered the caps).

Is this an indicator of a grounding problem? If so I am puzzled, since it used to work, and I have resoldered all the gorund connections.

Any suggestions?

gasjack 19th February 2004 12:16 PM


Originally posted by gasjack
I tried this method too.
When I say this method I mean the ones mentioned on this site:

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