Question about Altec Lansing ADA 885 Computer Speakers

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Humming in woofer

The woofer developed a hum. Not caused by cable inpur or bad connect. It appears that a filter cap may have failed on power supply. Where can I get a wiring diagram of the circuit board and a board component list?

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Re: Humming in woofer

A wiring diagram could be difficult if not impossible to find but you should'nt need one anyway.

You're correct in saying it's most likely a filter cap in the power supply, of which would be a larger electrolytic cap that may even display signs of being faulty. Look for leakage of crusty brown stuff on the end where the rubber seal and leads are, or possibly the other end, shrunken plastic skin, bulging or other signs of over heating. Replace any you find that have visual signs of failure.

Sometimes you cannot tell by looking if a cap is bad but it would'nt cost that much to replace the larger ones in there anyway. Open up the unit, write down the electrolytic cap values
you find, go buy replacements and replace em.

You're hearing 60 cycle hum so the filter(s) you need to replace will be quite large physically and have a fairly high micro farad value....such as 1000, 1500 or 2200.

When buying replacements, get as close to the micro farad rating as possible and buy at least the same voltage rating, or higher. Be sure to solder them in correctly, there is a negative and positive lead and you dont want to get those reversed or....

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Posted on Oct 23, 2007

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