Hi,
This subwoofer is not that old and developed a hum, even with no signal going in.
It was made in China - you guessed it. Do not have a schematic. Pulled the ckt assembly out. Workmanship is ugly, but do not see anything obvious. The ckt bd smells a bit , but it could be how these things smell :-)
There are 2 large caps 63V 6800uF in the PS. Would that be the culprit?
Regards,
Rich
Most likely.
anything obvious.
Anyone know where to get these? Googled a lot, but do not see many suppliers.
Rich
Coming in late on the thread, ... didn't see your original post. How loud is the hum? Can you hear any audio getting through? I repaired a powered subwoofer last year that exhibited a loud hum, but no audio was getting through. Turned out that one of the output transistors had shorted C-E and was causing extreme stress on the power supply. Replacing both output transistors fixed the problem.
-- Dave M MasonDG44 at comcast dot net (Just substitute the appropriate characters in the address) Never take a laxative and a sleeping pill at the same time!!
Mouser # 5985-85A-80V6800
Also, as the other gent said, you could have a large drain on the supply (bad output transistors).
Thanks for the hint Dave, it got me back to it. I was about to order caps (thanks for link Charles), but got back to more testing. The output transistors were OK, by VOM method. I started re-soldering some of the suspicious joints, as the whole thing did not show good workmanship. Also tightened the grounding screws. In that process I fixed the problem.
For those wondering, AR (Acoustic Research) is just a name anymore. Not even sure who owns the name. Stuff is made in China, and not very well at that.
Rich
loud
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