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Old 07-28-2012, 07:28 PM   #1
Join Date: Jul 2006
City & State: southern california
Posts: 28
Default Need tips in fixing APC 1500VA UPS having buzzing noise

I have a year 2005, APC UPS and one of the caps - an SIEMENS EPCOS 20uF 150V Capacitor - started making a buzzing noise.

This seems to be a AC, non-polarized capacitor and most local stores have it priced at ~$15 + tax!

They look like this:

I found caps of similar rating (20uF 250V) that are $3 each:

Do these look like a good replacement? Please let me know if there is something better suited (but perhaps more expensive) parts.

I also had a few questions:

0. Could I also replace these caps with these ones:

1. Is the buzzing because of the capacitor is bad or that a different component could be failing and having a secondary, audible effect on the capacitor?

2. Should not both these caps be interchangeable?

3. What could be the function of this SIEMENS EPCOS 20uF 150V Capacitor?

To act as part of a LC filter that puts out the sine wave?

4. Should I also change the MOVs on this thing and recap parts of it "just to be on the safe side"?

5. If replacing the MOVs is recommended, what surge rating/part number am I looking for?

Any tips/hints to kepping this nice UPS running would be greatly appreciated

This post also has some relevant information:

Last edited by vsmGuy; 07-28-2012 at 08:09 PM..
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