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If your PC’s power supply dies, you might have trouble diagnosing it;  you might wrongly blame the failure on the power switch or a bad motherboard.  You can unhook the cables from your PC, haul the whole computer to your local computer store, and pay $20 for them to tell you the power supply’s bad — or you can save some dough in the long run by picking up this CoolMax PS-224 Power Supply Tester.

The PS-224 will test the standard 20- or 24-pin motherboard power supply. An LCD screen displays the test results, and you don’t have to look up codes in a manual, like you do with cheaper models. The tester is accurate within +/- 0.1V, and it’ll set off an alarm if the voltage is too low, too high, or just not working. If you’re looking for an easy-to-use tester, this is it.

The CoolMax tester sells for $13 from PC parts stores.

LCD Power Supply Tester [CoolMax]
Street Pricing [Google]
Via Amazon [What’s This?]


7 Responses to CoolMax LCD Power Supply Tester

  1. ToolGuyd says:

    If your PC’s power supply dies, you might have trouble diagnosing it; you might wrongly blame the failure on the power switch or a bad motherboard.

    Generally, it’s relatively easy to differentiate between PSU and mobo problems or failures, especially if you tap into any of the many computer-enthusiast forums or message boards on the web. When it’s not so easy or simple to diagnose, chances are that a simple voltage tester like the one above will be of little use.

    The above voltage tester can also cause more problems than its worth; I can think of several scenarios where it can lead one to believe that there’s a problem with the mobo when the PSU is the real culprit.

    I’m not saying that this is a bad tool; I’m just trying to suggest that it’s not for those who are simply looking to avoid having to take their computer to the repair shop. In other words, it’s not for the inexperienced and computer unsavvy.

  2. I’ve built and trouble shot my fair share of computers and found that it’s difficult to tell if a power supply is faulty unless it’s totally dead and then you’d better pray it didn’t take out the motherboard, video card, hard drive, etc.. when it died.

    The other case is the computer is acting flaky — symptoms like locking up randomly or powering off after a period of time (possibly when it’s getting too hot) This may or may not be caused by the power supply.

    If I have a computer that’s acting funny, the first thing I do is run memtest to check the memory. You can Google and find the free version or download any one of a number of free emergency boot CD’s with it. Ubuntu live CD’s are handy to have too because they usually have a copy on them too.

    Then I’ll run a copy of Spinrite on the hard drive to make sure there aren’t any problems with the hard drive, sure its $80, but it’s paid for itself may times over. There are other utilities, some on the emergency boot CD’s, some you have to pay for that work too.

    If the problem still exists I’ll boot into a Live CD like Ubuntu mentioned above and see if the wackiness is just do to the installed operating system.

    Only after all that do I bother opening the case. You want to check air flow and that all the fans are working. Blow out the case with some canned air. Heat is the enemy. Unless you just bought the power supply or its over three years old 8 times out of 10 its something else.

    For $13, it probably won’t hurt to have this in your toolbox, but unless one of the power rails is totally dead or way out of spec, this tool probably won’t help. Many times the power supply will act fine unless it’s put under real world loads.

  3. Mr. Peepers says:

    I work on PCs for a living. If the power supply is under-rated, it could cause problems, but normally if the PC doesn’t power up, you can disconnect the power connector from the motherboard and use a paperclip to short the green wire (there is only one) with a black wire (there are several). If the PS does nothing, it’s dead.

    This tool won’t be able to tell if the PSU is underpowered, as it cannot do a load-test on the unit. It just tells you the zero-load voltages.

  4. Zathrus says:

    Agreed w/ Mr Peepers and Benjamen — doesn’t test under load, so it doesn’t do any better than jumping the green and black wires.

    To a certain extent memtest has the same issue (although at least it’s free) — a lot of memory problems only occur under load when the system is heating up, and memtest cannot duplicate that.

    As for under-rated PSUs… if it’s a really cheap knockoff from a few years ago it could be a problem. Otherwise it’ll be fine unless you’re running top-of-the-line multiple graphics cards and a Quad core CPU. I’ve run systems with 10 HD’s on a 350W PSU. Even a modern system with an “average” graphics card will be happy with a 350W PSU.

  5. rg says:

    I agree with Benjamin. For $13 this could be a handy tool for a quick check. To test the power under load, though, all you need to do is have the PC running, and insert thin probes for your voltmeter into the back of the motherboard connector.

  6. SuperJdynamite says:

    The problem with emulating the ATX “power on” signal by shorting pins is that once the power supply turns on it may turn right back off again because the voltage sense line wasn’t connected.

    Also, computer power supplies are switching type supplies which need some quiescent current running through them to work properly. They make cheap five watt resistors hooked to an ATX mobo plug and switch for this purpose.

    Also also, getting the supply to turn on absent any load really only tells you if the fan is working. It doesn’t tell you if all the voltage rails are working correctly as a fancier tester would.

  7. Captain Obvious says:

    I had another brand, got from TigerDirect:
    they DO put load on the PSU, which is why you can only run ’em for a few seconds
    ( the body of the tester is the heatsink )

    That *doesn’t* mean you can test whether it’ll supply XYZ # of watts, but maybe someone here wants to make their trade making such things?

    http://www.nolo.com/ for “how to patent stuff” books, so you can get to keep your market, after the “big boys” discover your product & set about destroying your “competition” from their world…

    Fair’s Fair, eh?


    Captain Obvious

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