How to find the 5v line on a power supply?

Discussion in 'Computer Information' started by Doc, Jun 6, 2006.

  1. Doc

    Doc Guest

    Someone has suggested I test the 5V line on a power supply with a range
    holding multitester to see if it's staying steady and within range. How do I
    locate this line?

    Thanks.
     
    Doc, Jun 6, 2006
    #1
    1. Advertising

  2. Doc

    beenthere Guest

    "Doc" <> wrote in message
    news:c0hhg.2312$...
    > Someone has suggested I test the 5V line on a power supply with a range
    > holding multitester to see if it's staying steady and within range. How do
    > I
    > locate this line?
    >
    > Thanks.
    >

    The cables that plug into your Hdrive are Red.Black.Black.Yellow
    Red and one Black = 5V.
    Yellow and one Black=12V.
     
    beenthere, Jun 6, 2006
    #2
    1. Advertising

  3. Doc

    Guest

    Doc wrote:
    > Someone has suggested I test the 5V line on a power supply with a range
    > holding multitester to see if it's staying steady and within range. How do I
    > locate this line?


    The pinout for the 20-pin ATX connector:

    http://xtronics.com/reference/atx_pinout.htm

    The pinout of the 24-pin connector (the most common type of 24-pin
    connector; there are 3 types):

    http://pinouts.ru/Power/btx_mbpower_pinout.shtml

    +5V = red
    +3.3V = orange (sometimes brown; blue with white stripe on some Dells)
    +12V = yellow
    +5V standby = purple
    -12V = blue
    -5V = white (not found on all power supplies)
     
    , Jun 6, 2006
    #3
  4. Doc

    Mike T. Guest

    "Doc" <> wrote in message
    news:c0hhg.2312$...
    > Someone has suggested I test the 5V line on a power supply with a range
    > holding multitester to see if it's staying steady and within range. How do
    > I
    > locate this line?
    >
    > Thanks.


    Someone gave you bad advice. If there is any question at all about a power
    supply, replace it. Don't **** around with a multimeter, or "range holding
    multitester". Voltage dips that can cause instability will not necessarily
    register on a multimeter, as the multimeter display won't update as fast as
    the voltage regulator switches. Plus, not all PSUs fail gracefully. They
    often destroy other connected components when they go. So while you are
    dinking around trying to get voltage readings, the PSU is a ticking time
    bomb that is ready to fry your mainboard (etc.) at any moment. So while you
    might "capture" a voltage drop, this is like taking a picture of an airplane
    as it explodes. Good to satisfy your own curiosity, but not good for the
    airplane.

    If you ever have a PSU that will show a bad reading on a multimeter, then
    the multimeter will be redundant at that point, as there will be NO DOUBT in
    your mind that the PSU is bad . . . even if the nearest multimeter is in the
    next zip code. -Dave
     
    Mike T., Jun 6, 2006
    #4
  5. I agree.. Risking your motherboard and everything else plugged into it to
    save $25 isn't worth it. Especially if your inexperenced at fixing power
    supplies.

    Here is a list of 400W power supplies for sale

    http://www.pricewatch.com/power_supply_for_case/2638-1.htm

    - Mike


    "Mike T." <> wrote in message
    news:4485ac69$0$15765$...
    >
    > "Doc" <> wrote in message
    > news:c0hhg.2312$...
    >> Someone has suggested I test the 5V line on a power supply with a range
    >> holding multitester to see if it's staying steady and within range. How
    >> do I
    >> locate this line?
    >>
    >> Thanks.

    >
    > Someone gave you bad advice. If there is any question at all about a
    > power supply, replace it. Don't **** around with a multimeter, or "range
    > holding multitester". Voltage dips that can cause instability will not
    > necessarily register on a multimeter, as the multimeter display won't
    > update as fast as the voltage regulator switches. Plus, not all PSUs fail
    > gracefully. They often destroy other connected components when they go.
    > So while you are dinking around trying to get voltage readings, the PSU is
    > a ticking time bomb that is ready to fry your mainboard (etc.) at any
    > moment. So while you might "capture" a voltage drop, this is like taking
    > a picture of an airplane as it explodes. Good to satisfy your own
    > curiosity, but not good for the airplane.
    >
    > If you ever have a PSU that will show a bad reading on a multimeter, then
    > the multimeter will be redundant at that point, as there will be NO DOUBT
    > in your mind that the PSU is bad . . . even if the nearest multimeter is
    > in the next zip code. -Dave
    >
     
    Michael Kennedy, Jun 6, 2006
    #5
  6. This one appears to be somewhat good,
    http://www.pctekonline.com/pen4readatxp1.html
    but any of them would work.. I'd just stay away from the really cheap ones.

    "Michael Kennedy" <> wrote in message
    news:...
    >I agree.. Risking your motherboard and everything else plugged into it to
    >save $25 isn't worth it. Especially if your inexperenced at fixing power
    >supplies.
    >
    > Here is a list of 400W power supplies for sale
    >
    > http://www.pricewatch.com/power_supply_for_case/2638-1.htm
    >
    > - Mike
    >
    >
    > "Mike T." <> wrote in message
    > news:4485ac69$0$15765$...
    >>
    >> "Doc" <> wrote in message
    >> news:c0hhg.2312$...
    >>> Someone has suggested I test the 5V line on a power supply with a range
    >>> holding multitester to see if it's staying steady and within range. How
    >>> do I
    >>> locate this line?
    >>>
    >>> Thanks.

    >>
    >> Someone gave you bad advice. If there is any question at all about a
    >> power supply, replace it. Don't **** around with a multimeter, or "range
    >> holding multitester". Voltage dips that can cause instability will not
    >> necessarily register on a multimeter, as the multimeter display won't
    >> update as fast as the voltage regulator switches. Plus, not all PSUs
    >> fail gracefully. They often destroy other connected components when they
    >> go. So while you are dinking around trying to get voltage readings, the
    >> PSU is a ticking time bomb that is ready to fry your mainboard (etc.) at
    >> any moment. So while you might "capture" a voltage drop, this is like
    >> taking a picture of an airplane as it explodes. Good to satisfy your own
    >> curiosity, but not good for the airplane.
    >>
    >> If you ever have a PSU that will show a bad reading on a multimeter, then
    >> the multimeter will be redundant at that point, as there will be NO DOUBT
    >> in your mind that the PSU is bad . . . even if the nearest multimeter is
    >> in the next zip code. -Dave
    >>

    >
    >
     
    Michael Kennedy, Jun 6, 2006
    #6
  7. Doc

    kony Guest

    On Tue, 6 Jun 2006 12:25:12 -0400, "Mike T."
    <> wrote:

    >
    >"Doc" <> wrote in message
    >news:c0hhg.2312$...
    >> Someone has suggested I test the 5V line on a power supply with a range
    >> holding multitester to see if it's staying steady and within range. How do
    >> I
    >> locate this line?
    >>
    >> Thanks.

    >
    >Someone gave you bad advice. If there is any question at all about a power
    >supply, replace it.



    That's rather ridiculous advice, since myriad problems could
    be caused by a poor or failing PSU but one can't go and
    replace the PSU every time Windows/etc hiccups. They would
    need to reduce the variables, using the tools at their
    disposal. A multimeter is one of those tools. Perhaps more
    important is this question:

    What did you think is a more valid indicator of PSU
    malfunction? Ok, a 'scope, but who that had one, would have
    an aversion to even using a 'meter?


    >Don't **** around with a multimeter, or "range holding
    >multitester". Voltage dips that can cause instability will not necessarily
    >register on a multimeter, as the multimeter display won't update as fast as
    >the voltage regulator switches.


    Actually, yes they will register. If the event was so short
    that a reasonable meter can't register it, it was also short
    enough to be buffered by the bulk electrolytics that just
    about any and all parts have. When a PSU problem becomes
    evident through system malfunction, more often it can be
    realized though a meter reading.

    >Plus, not all PSUs fail gracefully. They
    >often destroy other connected components when they go. So while you are
    >dinking around trying to get voltage readings, the PSU is a ticking time
    >bomb that is ready to fry your mainboard (etc.) at any moment. So while you
    >might "capture" a voltage drop, this is like taking a picture of an airplane
    >as it explodes. Good to satisfy your own curiosity, but not good for the
    >airplane.


    Same is true of a brand new replacement, if you have a PSU
    that might be working fine and introduce another PSU that is
    not yet qualified or proven working properly (a multimeter
    is nice here, too), simply adding that additional variable
    is a potential to cause damage or just unnecessary expense
    while not resolving anything. Replacement should be a last
    resort if other methods of determining PSU fitness can't be
    absolute.



    >
    >If you ever have a PSU that will show a bad reading on a multimeter, then
    >the multimeter will be redundant at that point,


    obviously not, because if one was measuring the PSU voltage
    there was still the suspicion that the PSU might not be the
    problem. One does not tend to replace parts that they feel
    might not be the problem unless they happened to have
    exhausted all other ideas and had a PSU lying around. How
    do they know the PSU lying around is good? I suppose they
    guess that it is if they don't take voltage readings. How
    many system owners happen to have that spare known-good PSU
    just lying around instead of having to order, wait, put the
    $ into that? The percent is close to zero, if the # of
    systems brought to me with a PSU problem is any indicator
    then they did not have the spare, and did not know it was a
    PSU problem else they would've just replaced it had they
    known exactly what was needed. A meter is a source of info
    so one does approach knowledge instead of guesses.

    >as there will be NO DOUBT in
    >your mind that the PSU is bad


    No, at that point of a bad reading you have exactly what you
    wanted, evidence to support your suspicion that it was, or
    refute that it wasn't, a PSU problem. You could have the
    ideal situation, KNOWING you have a psu problem based on the
    bad reading instead of only guessing. Guessing can be
    expensive if the system is anything more than a low-end box,
    or time consuming if this system is set up for specific
    needs/desires/etc and stores important data.

    If there is a strong suspicion that the PSU is bad but that
    the other parts are ok, it could be helpful to use an
    (invaluable) load instead of critical parts, but having
    tried the system with the PSU (pretty much manditory, that's
    what was running the system up until that point), odds are
    low that the PSU would have caused a problem, but be working
    enough that it's much of a risk to

    >. . . even if the nearest multimeter is in the
    >next zip code.


    Multimeter testing is never redundant, it is always the
    first source of real information. OTHER guesses, anecdotal
    evidence, software readings or even replacement of the PSU
    and finding it then resolving the situation, can only be
    redundant to actual determination though measurement, the
    multimeter being the obvious cost-effective tool to do it.

    This is all within a certain context though, that if one
    needed to be told to measure a supply voltage with a meter,
    they may not have the experience (or even the meter) to do
    it. In such cases it would be better to just take the
    system to an experienced technician if fast resolution is
    important. They could instead buy the replacement PSU for
    about the cost of the technician's bench fees, but they may
    not get the system working either... and if the owner isn't
    able to even use a multimeter, I'd have second thoughts
    about having them muck around inside a system (that already
    had a problem) TOO much. This may introduce yet another
    problem, instead of keeping things static except only to
    reduce the # of variables in troubleshooting.
     
    kony, Jun 6, 2006
    #7
  8. Doc

    Mike T. Guest

    > That's rather ridiculous advice, since myriad problems could
    > be caused by a poor or failing PSU but one can't go and
    > replace the PSU every time Windows/etc hiccups.


    I agree, to a point. But I still believe that replacing the power supply is
    a good idea, for many reasons. First, even good name-brand power supplies
    are surprisingly unreliable. The only component that fails almost as often
    is a floppy drive, and those are becoming more of a rarity. So it's good to
    have a spare power supply on hand anyway. You really lose nothing by
    swapping it. And, you reduce the risk that, if the other power supply was
    bad, it will damage other components. -Dave
     
    Mike T., Jun 6, 2006
    #8
  9. Doc

    Doc Guest

    "Mike T." <> wrote in message
    news:4485f61d$0$15296$...
    > > That's rather ridiculous advice, since myriad problems could
    > > be caused by a poor or failing PSU but one can't go and
    > > replace the PSU every time Windows/etc hiccups.

    >
    > I agree, to a point. But I still believe that replacing the power supply

    is
    > a good idea, for many reasons. First, even good name-brand power supplies
    > are surprisingly unreliable. The only component that fails almost as

    often
    > is a floppy drive, and those are becoming more of a rarity. So it's good

    to
    > have a spare power supply on hand anyway. You really lose nothing by
    > swapping it. And, you reduce the risk that, if the other power supply was
    > bad, it will damage other components. -Dave


    It might be a moot point, apparently this Compaq power supply isn't
    something you can just grab off the shelf, it's form is non-standard.
     
    Doc, Jun 6, 2006
    #9
  10. Doc

    Arno Wagner Guest

    In comp.sys.ibm.pc.hardware.misc Doc <> wrote:
    > Someone has suggested I test the 5V line on a power supply with a range
    > holding multitester to see if it's staying steady and within range. How do I
    > locate this line?


    It is red. Ground is black.

    Arno
     
    Arno Wagner, Jun 7, 2006
    #10
  11. Doc

    kony Guest

    On Tue, 6 Jun 2006 17:39:43 -0400, "Mike T."
    <> wrote:

    >> That's rather ridiculous advice, since myriad problems could
    >> be caused by a poor or failing PSU but one can't go and
    >> replace the PSU every time Windows/etc hiccups.

    >
    >I agree, to a point. But I still believe that replacing the power supply is
    >a good idea, for many reasons. First, even good name-brand power supplies
    >are surprisingly unreliable. The only component that fails almost as often
    >is a floppy drive, and those are becoming more of a rarity.


    Err, no. Floppy drives almost never fail, I have several
    that are a decade old and just needed the heads cleaned.
    Cheap fans tend to fail quite often, and motherboards.
    Maybe a PSU more often than that, but a PSU failure is not
    more likely than "everything else" combined, including the
    operating system itself becoming infected, malfunctioning or
    being undermined by user action (configuration, registry,
    drivers, etc).

    >So it's good to
    >have a spare power supply on hand anyway. You really lose nothing by
    >swapping it. And, you reduce the risk that, if the other power supply was
    >bad, it will damage other components. -Dave



    If the other power supply were bad, it has already been
    powering the system you now allege it would damage. I
    suggest buying decent enough PSU that you have safety
    shutdown on it. System had ran for years and it takes only
    a few seconds to use a multimeter. Perhaps your method of
    checking voltage needs reconsidered if you have actually
    damaged gear while trying to take a voltage reading.

    It's good to have a spare everything- board, video, power,
    etc, but in the end there has to be reasonable suspicion it
    was power, and without the multimeter reading there often is
    not reasonable suspicion until AFTER one had changed the PSU
    and then found the problem resolved... or not resolved, then
    it was a waste of money and time. PSU do not fail often
    enough that it is reasonable to simply assume it is bad and
    immediately replace it, unless the PSU was a very poor match
    to the system (or low quality generic) to begin with.
     
    kony, Jun 7, 2006
    #11
  12. Doc

    kony Guest

    On Tue, 06 Jun 2006 21:58:25 GMT, "Doc"
    <> wrote:

    >
    >"Mike T." <> wrote in message
    >news:4485f61d$0$15296$...
    >> > That's rather ridiculous advice, since myriad problems could
    >> > be caused by a poor or failing PSU but one can't go and
    >> > replace the PSU every time Windows/etc hiccups.

    >>
    >> I agree, to a point. But I still believe that replacing the power supply

    >is
    >> a good idea, for many reasons. First, even good name-brand power supplies
    >> are surprisingly unreliable. The only component that fails almost as

    >often
    >> is a floppy drive, and those are becoming more of a rarity. So it's good

    >to
    >> have a spare power supply on hand anyway. You really lose nothing by
    >> swapping it. And, you reduce the risk that, if the other power supply was
    >> bad, it will damage other components. -Dave

    >
    >It might be a moot point, apparently this Compaq power supply isn't
    >something you can just grab off the shelf, it's form is non-standard.
    >


    A lot of Compaqs were, but still used standard connectors to
    the mainboard. If the connector and wiring (voltages,
    pinouts) are the same then it need not be mountable in the
    chassis to just see if the system runs still or if there
    were another problem. Does the label on the PSU give any
    indicators? What system is this?

    As someone already mentioned, the drive plugs will have 5V.
    "usually" that is a red wire but proprietary gear including
    Compaq's has been know to stray from the standard color
    schemes from time to time. Looking at the 4 pin molex drive
    plug, with the tapered side of the connector facing up, 5V
    is the furthest left pin. If you accidentally had it upside
    down and it measured 12V, just take the reading of the
    opposite end since 5V is on one end, 12V on the other, and
    two (usually black) grounds inbetween.

    If this PSU is one Compaq made in the taller format, with a
    92mm fan on the back, it may not supply 5VSB (I don't recall
    for certain) but it supplies 3VSB. If you remain uncertain
    about anything take some good pictures and post to a server,
    linked here instead of posting the pictures themselves here.
     
    kony, Jun 7, 2006
    #12
  13. Michael Kennedy wrote:
    > "Mike T." <> wrote in message
    > news:4485ac69$0$15765$...
    >> "Doc" <> wrote in message
    >> news:c0hhg.2312$...
    >>> Someone has suggested I test the 5V line on a power supply with a range
    >>> holding multitester to see if it's staying steady and within range. How
    >>> do I
    >>> locate this line?
    >>>
    >>> Thanks.

    >> Someone gave you bad advice. If there is any question at all about a
    >> power supply, replace it. Don't **** around with a multimeter, or "range
    >> holding multitester".

    [snipped]
    > I agree.. Risking your motherboard and everything else plugged into it to
    > save $25 isn't worth it. Especially if your inexperenced at fixing power
    > supplies.
    >
    > Here is a list of 400W power supplies for sale
    >
    > http://www.pricewatch.com/power_supply_for_case/2638-1.htm
    >
    > - Mike


    I also agree as I lost six drives and every single board in a silent PSU
    blowout.

    Also, a computer PSU cannot be tested in the same way as your ordinary
    home or hobby PSUs. Some light reading;

    <http://computer.howstuffworks.com/power-supply.htm>
    <http://www.silentpcreview.com/article148-page1.html>


    Richard.

    --
    Two updates tools for 3D Studio Max
    <http://www.kdbanglia.com/maxtools.html>
     
    Richard Brooks, Jun 7, 2006
    #13
  14. Doc

    Guest

    Doc wrote:
    > "Mike T." <> wrote in message
    > news:4485f61d$0$15296$...


    > It might be a moot point, apparently this Compaq power supply isn't
    > something you can just grab off the shelf, it's form is non-standard.


    Directron has a good selection of nonstandard and micro ATX (mATX)
    power supplies. Don't try another supply unless its connector wires
    match in color with those of the original supply's, pin for pin,
    because some incompatible supplies use mechanically identical
    connectors but have the wire colors arranged differently.

    I'm not sure what a range holding meter is. Many meters will hold at
    the peak voltage read, but this won't be very useful for your purpose.
    Better would be a fast-responding meter that can record minimum and
    maximum readings, as this can record the worst fluctuations over time.
    Voltage meters can't diagnose all power supply problems, but in
    practice supplies are OK when all their voltages remain well within
    tolerance.
     
    , Jun 7, 2006
    #14
  15. Doc

    Guest

    kony wrote:
    > On Tue, 6 Jun 2006 17:39:43 -0400, "Mike T."
    > <> wrote:


    > Err, no. Floppy drives almost never fail, I have several
    > that are a decade old and just needed the heads cleaned.


    I had the highest failure rate with Mitsubishi 3.5" drives because
    their load mechanism would bind and cause the heads to clamp at the
    wrong time and scratch the disk or heads and sometimes even cause a
    head to tear off. My next most troublesome floppy drives were TEACs
    because their heads would go out of alignment.
     
    , Jun 7, 2006
    #15
  16. Doc

    Guest

    , Jun 7, 2006
    #16
  17. Doc

    kony Guest

    On 7 Jun 2006 04:23:55 -0700,
    wrote:

    >
    >kony wrote:
    >> On Tue, 6 Jun 2006 17:39:43 -0400, "Mike T."
    >> <> wrote:

    >
    >> Err, no. Floppy drives almost never fail, I have several
    >> that are a decade old and just needed the heads cleaned.

    >
    >I had the highest failure rate with Mitsubishi 3.5" drives because
    >their load mechanism would bind and cause the heads to clamp at the
    >wrong time and scratch the disk or heads and sometimes even cause a
    >head to tear off. My next most troublesome floppy drives were TEACs
    >because their heads would go out of alignment.



    a spot of grease might help on the former
     
    kony, Jun 7, 2006
    #17
  18. Doc

    kony Guest

    On 7 Jun 2006 04:16:11 -0700,
    wrote:

    >
    >Doc wrote:
    >> "Mike T." <> wrote in message
    >> news:4485f61d$0$15296$...

    >
    >> It might be a moot point, apparently this Compaq power supply isn't
    >> something you can just grab off the shelf, it's form is non-standard.

    >
    >Directron has a good selection of nonstandard and micro ATX (mATX)
    >power supplies. Don't try another supply unless its connector wires
    >match in color with those of the original supply's, pin for pin,
    >because some incompatible supplies use mechanically identical
    >connectors but have the wire colors arranged differently.
    >


    If it's the supply type I suspect it is, it's proprietary in
    pinout as well as form-factor. There were spares available
    online the last time I looked, the best luck at finding them
    is to enter the supply part/replacement numbers from it's
    label into Google, which may also provide an alternate part
    # that can also be sought.
     
    kony, Jun 7, 2006
    #18
  19. Doc

    Mike Berger Guest

    I'd classify that one as one of the really cheap ones.

    Michael Kennedy wrote:
    > This one appears to be somewhat good,
    > http://www.pctekonline.com/pen4readatxp1.html
    > but any of them would work.. I'd just stay away from the really cheap ones.
     
    Mike Berger, Jun 7, 2006
    #19
  20. Doc

    Franc Zabkar Guest

    On Tue, 06 Jun 2006 15:17:28 GMT, "Doc" <>
    put finger to keyboard and composed:

    >Someone has suggested I test the 5V line on a power supply with a range
    >holding multitester to see if it's staying steady and within range. How do I
    >locate this line?
    >
    >Thanks.


    The power supply monitors its own voltage rails and lowers the POK
    signal if any are below spec. When this happens, the motherboard
    should normally reset/restart itself. Note that the voltage you
    measure at the PSU will be somewhat higher than what you measure on
    the motherboard. This is because of voltage drops in the harness and
    at the connector itself.

    - Franc Zabkar
    --
    Please remove one 'i' from my address when replying by email.
     
    Franc Zabkar, Jun 7, 2006
    #20
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Silverstrand

    HEC Ace Power 580UB 580Watt power supply

    Silverstrand, Jul 23, 2005, in forum: Front Page News
    Replies:
    0
    Views:
    858
    Silverstrand
    Jul 23, 2005
  2. Silverstrand
    Replies:
    3
    Views:
    2,508
    Silverstrand
    Sep 1, 2005
  3. Silverstrand

    AOpen Prima Power AO700-12ALN 700W Power Supply Review

    Silverstrand, Aug 27, 2005, in forum: Front Page News
    Replies:
    5
    Views:
    1,474
    unholy
    Aug 29, 2005
  4. nick
    Replies:
    0
    Views:
    1,392
  5. XPD
    Replies:
    10
    Views:
    1,044
    Gregory Procter
    Nov 27, 2003
Loading...

Share This Page