Core Duo 20" Buzzes When UPS Backup Kicks In

[geekboy2000]

I pulled the plug on my APC BX900 to test it, and all went fine (it showed 53 minutes remaining). I noticed though that during the 2 minutes I had the plug out of the wall, and the UPS battery was powering the iMac, I heard a buzzing coming from the iMac (sounded to be near the top left corner somewhere). As soon as I put the UPS plug back in the wall, and it switched to line power, the buzzing stopped. I have also e-mailed APC about this, as it makes me wonder about the quality of the AC the thing puts out on battery power. Has anyone else experienced this? Is it to be expected? Thanks!

Mark

 

[dtravis7]

I have that APC unit. Will give it a try later and see what happens. It sounds like what you said, the quality of the AC the unit is producing when running from the Battery is causing noises from the Switching Power Supply. Will see if mine does it after dinner.

 

[geekboy2000]

I have that APC unit. Will give it a try later and see what happens. It sounds like what you said, the quality of the AC the unit is producing when running from the Battery is causing noises from the Switching Power Supply. Will see if mine does it after dinner.

Excellent, thank you! Looking forward to hearing what you hear.

Mark

 

[scottish]

The same thing happens to me when I use an inverter in my truck and my APC power backup, my ac laptop adapter (powerbook g4) is much louder than an ac outlet, but so far no harm is done. I think it has something to do with the converting DC (battery) to AC (Wall Plug) and sending the electric in lower hertz (than the standard AC 60Hz) but I don't know. I think it's just under powering the laptop a little but I don't think it will hurt it. Just my 2 cents.

 

[geekboy2000]

The same thing happens to me when I use an inverter in my truck and my APC power backup, my ac laptop adapter (powerbook g4) is much louder than an ac outlet, but so far no harm is done. I think it has something to do with the converting DC (battery) to AC (Wall Plug) and sending the electric in lower hertz (than the standard AC 60Hz) but I don't know. I think it's just under powering the laptop a little but I don't think it will hurt it. Just my 2 cents.

I appreciate the 2 cents, thank you. I suspect dtravis7 will report similar results, but I certainly hope the power supplies in these things would survive, if they were to ever run for the limit of the battery capacity. I know APC (and others) have equipment warranties under certain circumstances, but will they pay out if the device itself fried your computer?

Mark

 

[dtravis7]

Sorry it took me longer to get back to you. I never got back home till later.

Yes, if I unplug the AC Line from the APC, the top Right corner facing the back of the iMac buzzes. It seemed to work fine but one thing I saw was the screen seemed a bit dimmer. Not a very clean AC I guess.

 

[geekboy2000]

Sorry it took me longer to get back to you. I never got back home till later.

Yes, if I unplug the AC Line from the APC, the top Right corner facing the back of the iMac buzzes. It seemed to work fine but one thing I saw was the screen seemed a bit dimmer. Not a very clean AC I guess.

I believe there is a UPS option (in Energy Saver preferences) to dim the screen when on battery power), so perhaps that accounts for your dimming. As for the noise, thanks for reporting your findings. Do you think it's adversely affecting the iMac? Do you think it's safe to have the thing running for as long as it can on battery power? I'm inclined to think so, but it does sound kinda scary. Thanks again for checking/confirming.

I also found, after reading Apple discussions (and other forums), that the APC software may be redundant, as OS X versions 10.3.3 (and newer) support a USB connected UPS natively in Energy Saver preferences. Are you running APC's PowerChute at all? Many users seem to have just uninstalled the APC software.

Mark

 

[geekboy2000]

Well, today I returned the APC, and bought a Belkin F6C1500-TW-RK. I hear the software for it is awful (in fact I don't think Belkin has a current version for OS X on their site now), but it's not necessary, as the Energy Saver panel in OS X recognizes the UPS and provides an interface to options. As for the UPS itself, it's now charging, and although it's probably darn near fully charged, I'll wait awhile before doing a self-test. The reviews on the UPS seem good overall. Higher capacity, 8 conditioned battery backed-up outlets, but the real test (will the Intel Core Duo iMac buzz when on battery power) is yet to come. I'll report what I find.

Mark

 

[dtravis7]

For sure let us know what happens. That Buzz might not hurt anything but it is the Power Supply in the Mac for sure and that to me really does not seem right. I would hate to damage my switching power supply since in the newer iMacs is a PAIN to get to and change.

Thanks for your follow up.

 

[geekboy2000]

For sure let us know what happens. That Buzz might not hurt anything but it is the Power Supply in the Mac for sure and that to me really does not seem right. I would hate to damage my switching power supply since in the newer iMacs is a PAIN to get to and change.

Thanks for your follow up.

Okay, well, I couldn't resist doing the self-test. It kicked in fine, keeping the iMac up along with my 2 firewire drives - no problem. The iMac does still buzz when on battery power, but not nearly as loudly as I seem to remember with the APC. Would it be worth buying the Belkin if you already have the APC and are outside the window of being able to return it? Maybe not, unless you have another use for the APC unit. Definitely though, the Belkin seems to result in a substantially lower buzzing. I suppose now, there are two options:

1) Spend big money and try a Smart-UPS (or another brand with true sine wave output).
2) Pull the plug on this UPS and just sit and wait to see what happens.

Eventually the power will go out here, and I'm hoping I'm home when it does so I can closely monitor what happens. Either way though, I'm sure sooner or later, I'll find out if anything bad happens to the iMac when on battery power for as long as the UPS will support it.

Mark