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Old 08-04-2012, 12:12 PM   #14
Join Date: Jul 2006
City & State: southern california
Posts: 28
Default Re: Need tips in fixing APC 1500VA UPS having buzzing noise

Originally Posted by Toasty View Post
The title says 220vac, you're looking for 250vac. The capacitance is fine.

It's -only- a 12% difference in voltage, and for a trial to see if the noise stops, it's worth it. I would not leave it in place permanently.
Thank you Toasty for the advice -
The original cap that is making the noise (and the one I intend to replace) is SIEMENS EPCOS 20uF 150V Capacitor.

Given that, these seem to fit the bill just fine:

It's the age that worries me.

Originally Posted by Toasty View Post
Sealed caps like these are generally fine for a long time on the shelf. I would apply voltage slowly to make sure it is stable. A lamp in series with the power line. Or, try just feeding the cap through a lamp externally by itself, before installation. That would be a safer way, in case it decides to go *bang*!

If the lamp goes bright and stays that way, the cap is shorted.
I can do that - the lamp acts as a current limiter (in case the cap is shorted)? Would a regular 40W incandescent work for this?
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