[SOLVED] APC Back-UPS Pro 1500S Producing a Coil Whine-Like Squeal Without Load

[Maalikm]

I have just purchased an APC Back-UPS Pro 1500S uninterruptable power supply from Amazon the other day, and I've found a peculiar issue with it. Despite letting it to charge for almost a day, it produces a faint squeal still audible from about a meter away. This sound modulates between a lower and a higher pitch in a regular pattern.

This occurs even when the UPS has no load placed on it, and while it is plugged into a presumably good outlet.

• Is this an example of coil whine?
• Is this normal for this model of UPS, or is this unit defective?
• Is there a way to mitigate the sound without the need of hardware mods?
• Do all UPS's of this power level produce this sort of sound, or are there any pure sine wave 900w+ UPS's on the market that can operate silently?

Many thanks in advance for any advice y'all can give?

 

[Aeacus]

Is this an example of coil whine?

Yes.

Is this normal for this model of UPS, or is this unit defective?

No clue about that specific UPS model. Though, there have been specific lineups of PSUs that are prone to coil whine while another line of PSUs from same OEM are completely free from coil whine. Same goes for GPUs as well. So, entire model series could have that issue. But without having 2nd unit of the same model to test, all we can do, is guess.

Is there a way to mitigate the sound without the need of hardware mods?

Yes. Increase the white noise levels in your room, so the coil whine gets masked in it.

Do all UPS's of this power level produce this sort of sound

No.

are there any pure sine wave 900w+ UPS's on the market that can operate silently?

Yes.

I have two of these in use, in 780W capacity (line-interactive, true/pure sine wave),
link: https://www.cyberpower.com/hk/en/product/series/pfc_sinewave_gen._1#models

And there is 0 noise or coil whine from either of the two. I've had them for almost 3 years now (actually, next month is the time when they've been in service for 3 years exactly). For pics, look for my Skylake and/or Haswell builds in my sig.

Btw, your current UPS is outputting simulated sine wave (aka stepped approximation to a sinewave) and not true/pure sine wave,
specs: https://www.apc.com/shop/us/en/products/APC-Power-Saving-Back-UPS-Pro-1500/P-BR1500G