"Humming sound" when using UPS

[ibook300bb]

Anyone who is using APC UPS in their Macs?

I've noticed that when the battery of the UPS is ON (no AC source), humming sound is heard from the power supply of the Mac.

I've tried several Mac and same problem. More noise is coming from a G5 Tower.

No noise when I tried the APC UPS on a PeeCee.

Any help will be appreciated....

[Henjie]

Originally posted by ibook300bb
Anyone who is using APC UPS in their Macs?

I've noticed that when the battery of the UPS is ON (no AC source), humming sound is heard from the power supply of the Mac.

I'm using one.

You mean to say your Macs are getting power from the UPS' backup battery alone?


~Henjie

[ibook300bb]

During brown-out, the battery of the UPS is the only source of the G5.

I tried to simulate it by pulling out the AC plug and let the UPS run/supply the G5 using the battery of the UPS.

The humming sound is also heard even when the G5 is not turned ON.

I'm NOT using smart UPS.

[Henjie]

Originally posted by ibook300bb
During brown-out, the battery of the UPS is the only source of the G5.

I tried to simulate it by pulling out the AC plug and let the UPS run/supply the G5 using the battery of the UPS.

Oic, pag brownout pala. :-) Yeah, that's normal for a lot of G4 towers. Humming sound from the PSU fan (like it's hitting a grille or something) when running from a UPS' backup battery power. My previous Quicksilver 733 and my current MDD does the same thing. I guess they prefer AC power. ;-)

Not really an issue since you're supposed to turn off your computers as soon as you can whenever a blackout occur. :-)


~Henjie

[tdbur]

sounds like whatever speakers u have could be grounded. u need a 3 prong plug so you can ground your equipment properly

[Henjie]

Originally posted by tdbur
sounds like whatever speakers u have could be grounded. u need a 3 prong plug so you can ground your equipment properly

I use 3-pronged grounded plugs exclusively. The humming sound is from the PSU (standard China-made AC Bel, etc.). Maybe Apple should start using Antec or Enermax PSUs for its "pro" towers. ;-)


~Henjie

[ibook300bb]

tried a Smart UPS (pure sine wave) and the humming sound is gone.

But the price of the Smart UPS ia more that double compare to Line-InterActive one.