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Turning on an AT Power supply?

Discussion in 'Electronic Basics' started by, Jul 23, 2004.

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  1. (I was trying to use an ATX supply before, but it seemed more complicated,

    There is a switch on this AT-style power supply that I have now (of course).

    I stripped off the ends of one of the hard drive connectors, making sure
    don't touch when I hit the power switch.

    I hit the switch, and nothing happens.

    Do I have a bad power supply? Or do you have to have a load of some kind for
    it to work? I'm just trying to turn it on with nothing - so I can measure
    the voltage
    with a VOM. Starting at the beginning, as it were.

    The other day, I was diagnosing a friend's bad PC - it turned out to be a
    bad power supply. (ATX)
    The way I found out? I just plugged the AT power supply to the hard drive
    (which wasn't spinning up, BTW) and turned it on - voila! The hard drive
    spun up. By this I guessed that the power supply was bad (turned out to be
    the case).
    My point is, I had just 1 hard drive as a load, and the thing powered up
    just fine.
    (I'm pretty sure it's the same power supply, too)

  2. Puckdropper

    Puckdropper Guest

    You have to have a load. If the power supply detects no load, it shuts off.

  3. Do you know how much of a load? Would 50 mA be enough?

  4. Puckdropper

    Puckdropper Guest

    I normally use a floppy drive or some other computer component. I
    suppose you'll have to just try it and see.

  5. I tried a hard drive, and it USUALLY worked well - but the results were
    erratic. A few times it would shut off after 10 seconds, other times it
    would sound odd like the HD wasn't getting enough power - yet it stayed on.

    I'm thinking of adding another hard drive (maybe a 100 MB which I can get
    for free)

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