Hmm... my monitor buzzes whenever my APC unit kicks in.

[GRAFiZ]

If the power goes down and my APC kicks on, my Sony G400 monitor starts to buzz. It's loud enough to make me worry a bit.

Is this normal?

The odd thing is the APC allows me plenty of time to shut everything down and the screen stays perfect while on the backup, no wiggle or anything, but the back of the monitor just makes a buzz.

Should I worry???

[sjohnson]

The APC almost certainly does square-wave or modified square-wave AC instead of sine wave. Your monitor probably doesn't like it.

Yes, it could be bad. Or, it could just be a buzz. Hard to tell for sure.

[GRAFiZ]

Originally posted by sjohnson
The APC almost certainly does square-wave or modified square-wave AC instead of sine wave. Your monitor probably doesn't like it.

Yes, it could be bad. Or, it could just be a buzz. Hard to tell for sure.

Thanks for the info!

It's a APC ES 500 and the manual says this:

Waveform Type: Stepped approximation

:confused: :confused: :confused:

[sjohnson]

Instead of a square wave or sine wave, the APC approximates a sine wave (a smooth curve) by jumps (a "jagged" curve).

[GRAFiZ]

Originally posted by sjohnson
Instead of a square wave or sine wave, the APC approximates a sine wave (a smooth curve) by jumps (a "jagged" curve).

Thanks again for the info!

Another person told me:

"The AC output from the inverter in many UPSes is not a perfect sine wave. Its usually a stepped/modified "square" wave.

This non sine-wave output will in some cases cause the coils (usually, other components can vibrate too) in some power supplies to vibrate and emit a audible sound usually in the form of a 60hz buzz or 50hz if in a country that uses 50hz AC....

Some hot glue on the vibrating component will usually cure this."

Seems this has got to be the issue.

Hmm.. well, dont know what to do, I'll assue it'll be ok.

Thanks again!

[lalPOOO]

Sure its not the APC? I know when my power goes off my 1400VA starts to sound like a buzzing bee.

[Smizack]

Originally posted by sjohnson
Instead of a square wave or sine wave, the APC approximates a sine wave (a smooth curve) by jumps (a "jagged" curve).

Dirty electricity.