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Thread: Running hard drives from an old desktop power supply

  1. #1
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    Running hard drives from an old desktop power supply

    Hey, I've got an old 250 Watt power supply I salvaged from an old computer in a garbage heap. Can I use it to power hard drives and optical drives externally (I've got one of those cables that lets you run them outside your computer via USB)? Also, if it is rusty or damaged is there any risk to things I plug into it? Thanks.
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    Re: Running hard drives from an old desktop power supply

    Do yourself a big favor and go out and buy one of those power supply testers that you plug into it for testing. Otherwise get a multimeter and test them. But most power supplies will not kick up unless they are under load.

    Short answer, Dont trust it. It ended up in the garbage can for something. Test it first.

    Otherwise It should run them.

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    Re: Running hard drives from an old desktop power supply

    OK, thanks. It may be that the power supply doesn't work. The people who threw it away said it just died all of the sudden. I am going to get a power supply tester, but it will take a little while to get here. There are just two things I am still wondering about. Firstly, when turned on it makes an earsplitting ring. Is this a sign of being busted or something? Secondly, someone told me that power supplies only work when pulled from a computer in the 'on' position. I don't really understand how that would work, is this true?
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    Re: Running hard drives from an old desktop power supply

    "Secondly, someone told me that power supplies only work when pulled from a computer in the 'on' position. I don't really understand how that would work, is this true?"

    Too much BC bud, I think!
    Nonsense is an assertion of man's spiritual freedom in spite of all the oppressions of circumstance-- Aldous Huxley
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    Re: Running hard drives from an old desktop power supply

    Too much BC? Does this mean it's not true? And is the high-pitched ringing a sign of anything wrong? And I did just buy a power supply tester on eBay, so it should be here in a few weeks.
    Ubuntu: the next best thing to Mac OS X.

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    Red face Re: Running hard drives from an old desktop power supply

    Concerning the high pitched wine - This is an indication that the capacitors are bad in the power supply. I would not trust this thing hooked to anything. If you are good at electronics you can go in and replace them (all) but for the money its easier to buy a new power supply.

    Now, Power supplies for computers must be hooked to something in order to operate. This is a safety feature. You can test this out by unhooking all your connections from within your computer and plugging in the power supply and try turning it on. It will not. What ever you hook to the power supply is called the "load". The tester you buy for the power supply will represent a load to the p/s and thus it will kick up and run when being tested.

    Best to just through it out though. Unless you want to learn or are handy at soldering and some electronics experience.

    coffee

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    Re: Running hard drives from an old desktop power supply

    So if I hook the power supply tester to the 20-pin cable that usually hooks up to the motherboard, it should run? And the wine means that it is busted?
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    Re: Running hard drives from an old desktop power supply

    Quote Originally Posted by TimmyK. View Post
    So if I hook the power supply tester to the 20-pin cable that usually hooks up to the motherboard, it should run? And the wine means that it is busted?
    Each length of cable coming off the power supply is called a "rail". Common voltages used in the typical p/s are -12v, 5v, -5 and 12v. Now lets say a cap isnt doing its job right. You could end up with some pretty dirty power. That dirty power is going to screw with things on the mb and drives.

    Dirty power kills.

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    Re: Running hard drives from an old desktop power supply

    Forgive my noobishness, but what do you mean by "dirty power"? And the power supply tester will tell me whether or not it is dirty power, right? And if it isn't "dirty power", then with the power supply tester I should be able to run all my devices from it, can I not?
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    Red face Re: Running hard drives from an old desktop power supply

    Quote Originally Posted by TimmyK. View Post
    Forgive my noobishness, but what do you mean by "dirty power"? And the power supply tester will tell me whether or not it is dirty power, right? And if it isn't "dirty power", then with the power supply tester I should be able to run all my devices from it, can I not?
    Dirty power is basically when a rated amount of power really isnt what it says. So, 12v DC power on a graph would look like a straight line running across it. Perfectly level. But what would happen if it was kinda jagged instead of running straight across the graph? Its called dirty power because you are not getting the rated power all the time. This is why we have capacitors in the power supply. To kinda clean up those little problems. But dirty power happens when capacitors fail and then dirty power becomes a problem for the circuit its applied too. This is how most old p/s fail. The caps (capacitors) dry out and start delivering dirty power and then the circuit can fail or have weird effects.

    As long as the tester shows good for the power supply you can be reasonably sure it will function for your parts.

    Most p/s are tested using an Oscilloscope. That way you can see the actual Sign Wave that the p/s is producing. But the inexpensive testers will do for a quick check.

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