Power Supply sounds like a Jacob's Ladder on New APC UPS

Discussion in 'Community Discussion' started by coopdog, Apr 15, 2011.

  1. coopdog macrumors 6502a

    Joined:
    Oct 5, 2002
    Location:
    The Great Midwest
    #1
    I picked up an older APC 1500 XS with an external 47lb. APC XS/RS battery pack for $20 as-is from a surplus place ($1500+ retail). I let the unit charge overnight and with a PC pulling 200W and my screens, speakers, modem and airport extreme pulling less than another 100W I could get 120 min of backup power! I knew though, it wouldn't be in surplus if it was working like it should.

    Under a 700W load the UPS would fail it's self-test, but at my barebones (387W) it passed just fine even with batteries last replaced in 2005 according to the powerchute software. Everytime the UPS went onto battery, I would hear a constant electrical noise/hum, I thought it was the UPS inverters. I then tried to do the real test - unplug the UPS and see how long the batteries really last under a 387W load. The 6 12V batteries lost 10% every few seconds; batteries are dead. Near the end of the test I bent down and I could hear that the Jacob's Ladder arcing sound/hum was coming from my PC's power supply not the UPS! :eek:

    So yesterday 2 9Ah 12V batteries (Tempest) replacement batteries arrived. I installed them and removed the dead external APC battery pack. Now the estimated time is about 25 min, but it will actually last that long. I thought new batteries would have solved the problem. I have an APC 350 between my APC 1500 and my PC, every time I switch to battery power the 350 kicks in and my PC sounds fine for the brief time it's on. Here are my Kill-a-Watt readings:
    AC Utility Power: 120-121V, Power Factor: .97-.98
    Battery Power: 116V, Power Factor: .79

    Here is the sound:http://www.filedropper.com/powersupply It actually sounds more like a large hair trimmer...

    From my research, I found that PSUs don't like the square or sine-wave the older APC's put out, and the noise is the PSU's Power Factor correction? Especially if I can expand this UPS unit, I want to make sure it's not doing harm to the devices connected!

    Thanks for the help guys!
     
  2. coopdog thread starter macrumors 6502a

    Joined:
    Oct 5, 2002
    Location:
    The Great Midwest
    #2
    I figured out a few things:

    The older APC 1500 is using a stepped sine wave approximation, basically a square wave. Some say despite this frying sound coming from the PSU, the stepped "sine wave" is actually more efficient when transforming AC to the different DC voltages.:rolleyes: It's still not a sound I like coming from any device, especially my file and backup server. Since I have CCTV connected to the server, I want it to be on as long as possible, not just so I can have the time to shut it down properly...

    Apparently, NEVER connect a modern plasma or lcd TV or any solid state power supply to a square wave approx. output.

    No one has had this issue?
     
  3. iJohnHenry macrumors P6

    iJohnHenry

    Joined:
    Mar 22, 2008
    Location:
    On tenterhooks

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