View Single Post
Old 07-29-2012, 10:50 AM   #9
Join Date: Jul 2006
City & State: southern california
Posts: 28
Default Re: Need tips in fixing APC 1500VA UPS having buzzing noise

Toasty, quite an insightful post

Originally Posted by Toasty View Post
That being said, Epcos B32232 sheet attached. Metallized Polyester Film.
Yes, I posted the source link to this here:

Originally Posted by Toasty View Post
Noise may very well be from another component. Usually, by time these caps start buzzing, it's too late. I've never seen one fail. The orange drop caps nearby (also MPF) I see fail when high spikes on the line occur. Telltale is a change in color or a crack/burn in the casing.
The caps are light brown, and hence, a shade darker than orange, but perhaps they were that color to begin with?

Originally Posted by Toasty View Post
Be nice to see a pic of the whole area. I'm assuming the pic in #3 is your unit.
Correct, and I posted closeup shots here:

Also, a user on this forum did a video of him repairing a similar unit :

This has a similar layout as mine and would give you an idea what the board is laid out like

Originally Posted by Toasty View Post
Could also be noise from another device on the line this is connected to. Cheapo Chinese fluorescent ballasts radiate that and can be feeding it onto the line. Try moving it to another circuit.
I was under the same impression, but the noise also appears when I take the unit off the line and run it off batteries on heavy load (the noise wen running on batteries increase with load with almost no noise when lightly loaded ~11W)

Originally Posted by Toasty View Post
You have enough "noisemakers" nearby to probably discount these as failures. I see 6 relays and several coils/chokes nearby. That entire bank of rectifiers/FETs can also be noisy at times.
Agreed. However, the noise manifests in the region around the EPCOS.

So the noise could be from either:

1. The EPCOS cap itself
2. The chicklet caps around the EPCOS
3. Another component that is making these caps noisy (This is what I am most afraid of - that even after replacing these caps, the noise remains, as the root cause is somewhere else to begin with )

Originally Posted by Toasty View Post
PS: Make sure any output side power strips are -NOT- surge protected. They -say- sine wave, but spikes do occur and will quickly take out the MOVs, especially if lightly loaded.
Hmm - what you are saying is - trust the UPS with surge protection and just have power taps from the UPS output?

Otherwise, the UPS could likely create spikes itself in the output, which can take out MOVs downstream?
vsmGuy is offline   Reply With Quote