Connect with us

How to test a power supply ?

Discussion in 'Electronic Design' started by Skybuck, Jun 9, 2007.

Scroll to continue with content
  1. Skybuck

    Skybuck Guest

    Hello,

    Some have suggested to buy a voltmeter and then test the power supply.

    Since computers have special plugs and such, how would one go about
    testing the power supply ?

    Are there special plugs necessary ?

    (Not that I would ever try it, way to dangerous !)

    Do you have a link to a website with some pictures ?

    Bye,
    Skybuck.
     
  2. Inglo

    Inglo Guest

    How about buying a power supply tester, they sell them pretty cheap.
     
  3. Phil Weldon

    Phil Weldon Guest

    'Skybuck' wrote:
    | Some have suggested to buy a voltmeter and then test the power supply.
    |
    | Since computers have special plugs and such, how would one go about
    | testing the power supply ?
    |
    | Are there special plugs necessary ?
    |
    | (Not that I would ever try it, way to dangerous !)
    |
    | Do you have a link to a website with some pictures ?
    _____

    All mains voltage is contained within the metal ATX power supply box. Just
    follow basic safety proceedure used when working on ANY device connected to
    mains voltage (i.e. don't stick screwdrivers into the supply when it is
    plugged in.)

    Keep in mind that mains voltage is ALWAYS present in the ATX power supply
    EVEN when the system front panel switch is turned off AND the power switch
    (if any) on the back of the power supply is turned off as long is the power
    cord is plugged into the mains.

    The System front panel switch just handles logic level voltages. However,
    you must supply a POWER ON logic level TO the power supply to get it to turn
    on.

    Diagrams and specifications for the ATX power supply are at
    http://www.formfactors.org/developer/specs/ATX12V_PSDG_2_2_public_br2.pdf .
    Included are pinouts for the various power plugs.

    A digital voltmeter should be used for measuring voltages.

    The voltages under no load will not be representative of the voltages under
    load. Voltage measurements when the system is operating are much more
    useful. Thus the reason for system monitoring chips.

    A good computer repair shop is recommended.

    Phil Weldon

    | Hello,
    |
    | Some have suggested to buy a voltmeter and then test the power supply.
    |
    | Since computers have special plugs and such, how would one go about
    | testing the power supply ?
    |
    | Are there special plugs necessary ?
    |
    | (Not that I would ever try it, way to dangerous !)
    |
    | Do you have a link to a website with some pictures ?
    |
    | Bye,
    | Skybuck.
    |
     
  4. Hi, stranger!
    To _test_ a component to some designed specs is NOT starting by buying
    an instrument(s). Maybe first learn what it does, the PSU, and then
    build(?) a laboratory to tackle this job.
    Then you will be surrounded by voltmeters, ampermeters, passive and
    active loads and so on including plugs and wires.

    Good hunting

    Stanislaw
     
  5. neon

    neon

    1,325
    0
    Oct 21, 2006
    on a xt type of power supply do not make the mistake of plug it in without a load not unless you would like to do that only once. the voltage out means nothing not unless there is a load the same applies to batteries.
     
  6. Nonymous

    Nonymous Guest

    http://www.compusa.com/products/product_info.asp?pfp=cat3&product_code=
    332184&Pn=ATX_12V_Version_2_0_Power_Supply_Tester

    They have them right in the store if you have a CompUSA local to you.
     
  7. Just buying anything is useless before you know
    what you wnat to measure. Are you interested in
    the voltage under load? In the temperature
    behaviour under load ? In the spikes dependent
    on the load ? In the bandwidth under load ?
    There is tons to measure.

    Rene
     
  8. Make sure you get a voltmeter with a USB connector, in case you have
    to reinstall the OS on the voltmeter


    martin
     
  9. Phil Weldon

    Phil Weldon Guest

    'martin' wrote:
    | Make sure you get a voltmeter with a USB connector, in case you have
    | to reinstall the OS on the voltmeter
    _____

    Actually, you CAN get Digital Multimeters with serial and USB ports - for
    logging, and, I suppose, for flash updates for the more sophisticated DMMs.

    Phil Weldon

    | On Fri, 08 Jun 2007 21:11:17 -0700, in sci.electronics.design Skybuck
    |
    | >Hello,
    | >
    | >Some have suggested to buy a voltmeter and then test the power supply.
    | >
    | Make sure you get a voltmeter with a USB connector, in case you have
    | to reinstall the OS on the voltmeter
    |
    |
    | martin
     
  10. Yes I know, but considering all the problems the OP is having with
    bios and stuff, I thought I would just add to his confusion


    martin
     

  11. They are basically useless. The only way to fully test a PSU is under load.
    If has to be plugged in and the computer needs to be running. A voltmeter is
    the only way to go. Just because a PSU works when its not under load ie
    using a PSU tester does not mean it wont fail under load, once its gotten
    good and warm.

    Dan
     
  12. d.schatkamer

    d.schatkamer Guest

    You better change your name in stupid american like the rest.
    Stop crossposting !
    fup set
     
  13. Frank McCoy

    Frank McCoy Guest

    In alt.comp.hardware.pc-homebuilt "Angry_American"
    I wouldn't say that.
    I've replaced about a half-dozen power supplies by different makers over
    the past three to four years; and *every single one* failed to properly
    power-on the cheap $20 tester I have. Only GOOD PSUs brought it to
    life.
    That is true ... but only "to fully test".
    A Power-Supply-Tester is a handy way to check a failed supply and
    confirm it has failed. Only if it says the supply is *good* and yet the
    system shows signs of power-supply failure do you need more extensive
    tests. When the Power-Supply-Tester fails to power-on when hooked to a
    PSU, taking voltage measurements afterwards is overkill.

    Just toss the thing.

    And MOST bad supplies won't power up even a cheap tester.
    It's quick and dirty; but definitely NOT useless.
    But if it fails the PSU tester, then why go to the bother of all the
    other shit? And, in most cases of a failed supply, it WILL fail.

    A HELL of a lot quicker too, than probing around with a voltmeter.
    Just don't trust it to find marginal cases; or especially don't expect
    it to find power supplies that were underpowered when bought; unless, of
    course, the being underpowered is what caused the PSU to fail.

    That's why you keep BOTH in your toolbox.
     
  14. Unless it has a digital readout, it's not much good except for telling
    if the PSU is completely dead or not. The one I tried said that my
    PSU was fine even though the +12V rail was too low to let HDs spin.

    A cheap digital multimeter and a bent paperclip to short the green
    Power-On line to either of the black ground lines next to it are
    usually good enough, but sometimes a couple of 10 ohm, 8-10 watt
    resistors are needed to load down the +5V (connect each between a red
    wire and a black wire).
     
  15. default

    default Guest

    If you don't open the case there's nothing that should bite you.

    You need a "dummy load" to load down the PS to test it (many won't
    even power up without a load of some sort)

    None of the commercial units, I've seen, put enough load on a PS to
    stress it (pulling 10 watts from a 300+ watt supply isn't a real
    test).

    There were some dummy load schematics on the web. What would be good
    (don't know if anyone is selling it) would be a plug that can be put
    between the PS connector and mobo and analyze and monitor the actual
    voltages with some lights to tell you if the power is clean.
     
  16. : > How about buying a power supply tester, they sell them pretty cheap.
    : >
    :
    :
    : They are basically useless. The only way to fully test a PSU is under load.
    : If has to be plugged in and the computer needs to be running. A voltmeter is
    : the only way to go. Just because a PSU works when its not under load ie
    : using a PSU tester does not mean it wont fail under load, once its gotten
    : good and warm.
    :

    I don't disagree but I do wish I'd had the cheapo $10-$15 ps test
    thingie around before I hooked up a RAID array to a brand new Ultra
    power supply that shipped from the factory with its +5 swapped with
    +12. I didn't bother testing it with a voltmeter ahead of time as I'd
    never seen one of these switchers come on without some sort of even
    minimal load.
     
  17. JackShephard

    JackShephard Guest

    SkyTard,

    In the motherboard box or at the PC store, there are little splitter
    cables that split a supply line into two lines. You cut one end off one
    of the splits and plug it in to have four wires available. That is only
    two of the supply rails, however. The ATX connector (also needed) is a
    product you would buy on digi-key or the like from AMP, but you'll also
    have to buy wire and pins and a crimper.

    Again, if you do not already know these SIMPLE, BASIC things, you have
    no business delving into them.

    Since you obviously don't even know how to attach test devices to a PC
    supply, you certainly would not have the first clue about testing one
    under loaded conditions, whether they (the loads) be fixed or variable,
    and that is what is needed to test the supply, not just some lame, simple
    voltmeter test. PC supplies also have a nasty habit of shutting down
    when loading changes on certain rails, so you also have to have a good
    deal of familiarity with the ATX PS Design specification as well, which I
    am certain you do not.

    You were way over you head when you started messing with your PC, and
    you are certainly way over your head on testing the supply for it. You
    likely would not even have a clue how to properly load it, much less what
    you need to look at or for when it is loaded.

    Do you even know what the word "ripple" means?

    You cross posting Usenet retard.
     
  18. JackShephard

    JackShephard Guest


    Not a very bright response. That places you damn near at his level.
     
  19. JackShephard

    JackShephard Guest

    One cannot properly OR safely test a supply hooked up to the computer
    either.

    It needs load testing, but ON THE BENCH. It needs to have each rail
    examined with a scope to look at the ripple voltages on each rail when
    they are all under their full rated loading spec.

    That's where one will see the big difference between the cheap shit and
    the well made supplies.

    It's just like the bad old days of the seventies when car stereo makers
    had misleading and erroneous claims about their audio output power
    levels. Yeah, it puts out 15 Watts per channel... at ten percent
    distortion!
     
  20. JackShephard

    JackShephard Guest


    The claim that is trademarked is bullshit. What that is is public
    domain, dipshit.

    The ONLY proper way to test a PC supply is FULLY loaded to the spec of
    that particular supply, and with a scope to examine the ripple voltage so
    that one can test for compliance to the ATX PS Specification.

    It may look fine, it may supply full voltage, but if the ripple is too
    high, then it is really FOOL Voltage!

    The ATX spec is very stringent on ripple, as that is what causes
    failures in logic, and we can't have that on something we would call a
    computer.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-