Testing a power Supply

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Slightly off-topic, but relevant to many - I hope.

I have a power supply that was given to me. The previous owner is
suspicious that it may be the cause of all his PC woes (hence the free gift)
How do I go about testing it to see if it is OK in regards to correct
voltages.

It's laying on my desk at the moment. Do I have to install it in a case to
test it, or can I test it 'on the bench'?
What exactly am I looking for anyway?
The 20 pin connector has many colored wires, Are the colours significant?
How do I test for 12, 5 and 3 volts??

Sorry for the newbie-like question, but It would be a shame to throw it in
the garbage without checking it out first.

Many thanks
Richard
5 answers Last reply
More about testing power supply
  1. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    here are 3 different PSU testers
    take your pick

    http://www.dansdata.com/quickshot018.htm
    http://www.directron.com/tester1.html
    http://www.casemodgod.com/cmg/Reviews-story--51.html


    "Life should NOT be a journey to the grave with the intention of arriving
    safely in an attractive and well-preserved body, but rather to skid in
    sideways, chocolate in one hand, margarita in the other, body thoroughly
    used up, totally worn out and screaming, "WOO HOO what a ride!"


    --
    It's so much easier to suggest solutions when you don't know too much about
    the problem
    "Richard Lees" <r_lees001@hotmail.com> wrote in message
    news:ON7oe.41071$_r1.1290860@news20.bellglobal.com...
    > Slightly off-topic, but relevant to many - I hope.
    >
    > I have a power supply that was given to me. The previous owner is
    > suspicious that it may be the cause of all his PC woes (hence the free
    > gift)
    > How do I go about testing it to see if it is OK in regards to correct
    > voltages.
    >
    > It's laying on my desk at the moment. Do I have to install it in a case
    > to test it, or can I test it 'on the bench'?
    > What exactly am I looking for anyway?
    > The 20 pin connector has many colored wires, Are the colours significant?
    > How do I test for 12, 5 and 3 volts??
    >
    > Sorry for the newbie-like question, but It would be a shame to throw it in
    > the garbage without checking it out first.
    >
    > Many thanks
    > Richard
    >
    >
    >
    >
    >
  2. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    In article <ON7oe.41071$_r1.1290860@news20.bellglobal.com>, "Richard Lees"
    <r_lees001@hotmail.com> wrote:

    > Slightly off-topic, but relevant to many - I hope.
    >
    > I have a power supply that was given to me. The previous owner is
    > suspicious that it may be the cause of all his PC woes (hence the free gift)
    > How do I go about testing it to see if it is OK in regards to correct
    > voltages.
    >
    > It's laying on my desk at the moment. Do I have to install it in a case to
    > test it, or can I test it 'on the bench'?
    > What exactly am I looking for anyway?
    > The 20 pin connector has many colored wires, Are the colours significant?
    > How do I test for 12, 5 and 3 volts??
    >
    > Sorry for the newbie-like question, but It would be a shame to throw it in
    > the garbage without checking it out first.
    >
    > Many thanks
    > Richard

    Pinout is on page 19:
    http://www.formfactors.org/developer/specs/atx/atx2_1.pdf

    (pin 1) (pin 11)
    +3.3VDC +3.3VDC
    +3.3VDC -12VDC
    COM COM
    +5VDC PS_ON# <--- connect to COM to start PSU.
    COM COM <--- Plastic lock latch is
    +5VDC COM <--- next to these pins.
    COM COM
    PWR_OK -5VDC
    +5VSB +5VDC
    +12VDC +5VDC

    You have six voltages to test:

    +5VSB - standby supply for sleeping computer, also powers start up
    circuit on PSU. If not at full 5 volts, PSU may not work
    properly, as supervisor cct in PSU will not be properly powered.
    For the PSU to be completely turned off, PS_ON# should float
    near the same +5VSB voltage. When PS_ON# is grounded (to COM),
    the supply runs.
    +3.3VDC - Used by PCI/AGP cards for chip power. May be used for
    memory power, via linear regulation.
    +5VDC - Used to power Vcore switching regulator on Asus AthlonXP boards.
    Video card power, disk drive power.
    +12VDC - Used to power Vcore switching regulator on P4/Athlon64 boards.
    Video card power, disk drive power.
    -5V - Historically, used for ECL or really old tech, three rail
    DRAM memories. Maybe some kind of video card RAMDAC.
    Typically not used today. Possibly used in linear (op amp)
    circuits.
    -12V - On Asus boards, can be used for RS-232 converter chip. Also
    potentially used for op amps in linear regulators. It is hard
    to say which negative rail Asus would use on their op-amp
    circuits, as negative swings are not really required. In any
    case 0.1 amps of consumption on a motherboard is probably
    a reasonable estimate.

    A quick test, is to connect PS_ON# to a COM pin. The plastic lock
    latch will help guide you to the right cluster of pins. The purpose
    of a quick test, is just to check that the PSU fan starts to spin.
    That would only prove that the supervisory circuit is capable of
    turning on, in a situation where, say, a motherboard refuses to start.

    To quantify operation, you need a load on the PSU. One choice
    is to apply the minimum load necessary for proper regulation.
    Some supplies have minimum current loads specified on the label
    on the side of the supply. If you draw that minimum current, then
    the output is guaranteed to be within 5% of the proper voltage.
    One would hope, under those conditions, it is a lot closer than
    that.

    To measure the output, you will need a voltmeter. Home units are
    typically not that good, and my $100 CDN meter is good to about
    1.5% to 2% accuracy, depending on range used. That means there is
    room for doubt in the readings, to those precentages.

    Drawing the minimum supply current ensures the outputs will be in
    spec. A second test would be a load test, using a representative
    load. Using a load like this, proves the power supply will be
    able to run a real motherboard - the load circuit takes the risk
    out of having to connect a real motherboard, to prove the power
    supply works.

    Here are some representative loads measured on systems here:

    A7N8X (3200+) P4C800-E (2.8GHz)
    3 DIMMs 4 DIMMs
    +3.3V 5.5A 13.75A
    +5.0V 16 + 5.5A 0.6 + 5.5A
    +12.0V 0.5 + 0.9A 6.4 + 0.9A

    The added currents shown above (5.5A and 0.9A) are for a 9800pro
    AGP video card while gaming. The 6.4A for the P4, is 6 amps for the
    processor and 0.4A for the processor fan.

    To build a load tester, you will need a cable harness (snip up
    a 20 to 24 pin adapter cable - even a 24 pin connector can be
    used for the project, as there is only one way to plug a 20 pin
    power supply into such a connector, and have all the pins
    connected). You will also need resistors.

    To work out a load resistance:

    V/I = R_load = 3.3V/5.5A = 0.6 ohms

    V*I = power_dissipation = 3.3V*5.5A = 18.15 watts
    Can also be calculated as V*V/R, if only V and R are known.

    More than one resistor can be used to build a load. Two 0.3 ohm
    resistors put in series, would give a 0.6 ohm load. Two 1.2 ohm
    resistors put in parallel, would give a 0.6 ohm load. The
    power dissipated in each case, is now split between the two
    resistors, so two smaller resistors can be used to make a larger
    resistor. In the third example below, a square matrix of resistors
    of equal value, can be used. In that case, each resistor only
    needs to handle 1/9th of the total power to be dissipated.

    ----- 0.3 ------ 0.3 ------ = 0.6 ohms

    ---+--- 1.2 ---+--- = 0.6 ohms = R1*R2/(R1+R2)
    | |
    +--- 1.2 ---+

    ----+--- 0.6 ---+--- 0.6 ---+--- 0.6 ---+----- = 0.6 ohms
    | |
    +--- 0.6 ---+--- 0.6 ---+--- 0.6 ---+
    | |
    +--- 0.6 ---+--- 0.6 ---+--- 0.6 ---+

    (Hint - the parallel configuration may be easier to construct
    - a ladder constructed of stiff copper house wiring
    could be used to mount resistors in parallel.)

    There are many styles of power resistors. In the two examples
    below, one is designed for free-standing operation. The other
    one is intended for use with a heat sink (but no thermal data
    is given?). In the load examples in the table above, the 5V
    at 21.5 amp load would be the hardest one to cool, at 108 watts.
    For some resistors I've been looking at, they appear to be
    intended to dissipate the rated power without forced air, but
    if you run a fan over them, you might not burn yourself on
    them.

    There are some candidate resistors here. To reach our target
    resistances using these products, in some cases, multiple
    resistors are needed (in parallel) to get the resistance low
    enough. In other cases, multiple resistors are needed to get
    enough power handling capability. As the Digikey catalog
    doesn't have all possible resistor values, sometimes a higher
    power resistor must be substituted to get a necessary resistor
    value. (I.e. The selection process is a mess. I did all the
    math necessary, to build my load box, while standing in front
    of the power resistor display rack at my local electronics
    store. That is because you never know what resistors will be
    in stock...)

    FVT series: The FVT are fixed value resistors. Vitreous enamel
    looks to be a high temperature material, so you can burn the
    hell out of these.

    http://dkc3.digikey.com/PDF/T052/1075.pdf

    The TMC ones (second item from top of page) have a casing suitable
    for use with a heatsink. Now, there simply isn't enough data
    here, to design with these and understand what you are doing.
    (No thermal resistance data, for example.) How many of these
    could you bolt to one heatsink ?

    http://dkc3.digikey.com/PDF/T052/1076.pdf
    ==> http://www.heiresistors.com/aluminum.htm

    A7N8X (3200+) P4C800-E (2.8GHz)
    3 DIMMs 4 DIMMs
    +3.3V 5.5A => 0.6ohm 18W 13.75A => 0.24ohm 45W
    +5.0V 21.5A => 0.23ohm 108W 6.1A => 0.82ohm 31W
    +12.0V 1.4A => 8.6ohm 17W 7.3A => 1.64ohm 88W
    totals 143W 164W

    now select some resistor combinations...

    A7N8X (3200+) P4C800-E (2.8GHz)
    3 DIMMs 4 DIMMs
    +3.3V 5.5A => 0.6ohm 18W 13.75A => 0.24ohm 45W
    (3) FVT25-2.0-ND in (4) FVT50-1.0-ND in
    parallel $9.93 parallel $19.16

    +5.0V 21.5A => 0.23ohm 108W 6.1A => 0.82ohm 31W
    (4) FVT50-1.0-ND in (1) FVT50-1.0-ND parallel with
    parallel $19.16 (1) FVT50-5.0-ND $9.58

    +12.0V 1.4A => 8.6ohm 17W 7.3A => 1.64ohm 88W
    (1) FVT25-10-ND $3.28 (1) FVT100-2.0-ND parallel with
    (1) FVT25-10-ND $11.49

    -5V (1) FVT25-25-ND $3.28 (1) FVT25-25-ND $3.28
    will draw 0.2 amps will draw 0.2 amps

    -12V (1) FVT50-50-ND $4.50 (1) FVT50-50-ND $4.50
    will draw 0.24 amps will draw 0.24 amps

    +5VSB (1) FVT25-10-ND $3.28 (1) FVT25-10-ND $3.28
    will draw 0.5 amps will draw 0.5 amps

    Total $43 for resistors $51 for resistors
    + 80mm fan for cooling 80mm fan for cooling

    Wiring the A7N8X example:

    +3.3 ----+----+----+
    | | |
    2ohm 2ohm 2ohm
    | | |
    COM ----+----+----+

    +5.0 ----+----+----+----+
    | | | |
    1ohm 1ohm 1ohm 1ohm
    | | | |
    COM ----+----+----+----+

    +12.0 ----+-----------+
    | | (red)
    10ohm 80mm fan
    | | (black)
    COM ----+-----------+

    -5V ----+
    |
    25ohm
    |
    COM ----+

    -12V ----+
    |
    50ohm
    |
    COM ----+

    +5VSB ----+ PS_ON+ ----+
    | |
    10ohm (toggle switch)
    | |
    COM ----+ COM ----+

    Note: This is just to give you some ideas for how to construct
    your own PSU load box. If you can find cheaper resistors, you
    will be able to use more of them, and perhaps have them run a
    bit cooler. The FVT100-2.0-ND resistor on the right hand example
    is going to get pretty hot. When using the 80mm fan, it might
    be a good idea to build a "wind tunnel" with sheet metal, to
    shape the airflow around the resistors.

    You will also want some place to probe with your volt meter.
    So, if building vertical ladders with copper wire, screwed down
    to a wooden base, leave enough excess wire on the ends of the
    ladder, so you can probe with the voltmeter.

    When testing the PSU, run it with the representative load for
    a couple of hours, and see if all voltages are still within
    5% of the stated values.

    There is no point testing the "full power" rating of the
    supply, because many commonly available power supplies will
    disappear in a cloud of smoke if you do that. The idea of a
    load test, is to present a representative load, similar to
    the motherboard you will be using.

    The power supply test products that have LED indicators on
    them, could be using a window comparitor circuit. For example,
    if one analog comparator checks for 11.4V, and another one checks
    for 12.6V, using some logic gates, those comparators can be
    used to check that the voltage is within the "window" of
    11.4V <= V_out <= 12.6V. Under those conditions, the LED comes
    on. If the voltage is outside the window, the LED goes off.
    You can get the same information by simply measuring the output
    with a voltmeter.

    P.S. I'm not responsible if you burn yourself on the resistors!
    They can get really hot (resistors rated to 350C degrees), so
    don't be poking them with your fingers. As long as there is a
    decent airflow with the cooling fan, that should prevent them
    from getting all the way to 350C. Make sure there is some
    separation between the resistor and any combustable material.
    Using bare copper wire to hook up the resistors will avoid
    the embarrassment of having the wire insulation start to burn.
    And, above all, don't run this gadget unattended - turn it off
    and unplug it, if you leave the room. Think of having to explain
    to the insurance agent about power supply testers :-)

    Is it worth $100 for test gear (tester+voltmeter), to test a
    $30 power supply ? Only you can answer that. I built my tester,
    just to make sure I don't kill any expensive motherboards. My
    tester draws less current than the examples above.

    Have fun,
    Paul
  3. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    Geez -

    I'm going to have to go to night school!
    But I'll try to understand your reply and see if I can figure it all out.
    Thanks for the thorough reply

    Richard


    "Paul" <nospam@needed.com> wrote in message
    news:nospam-0406050744410001@192.168.1.178...
    > In article <ON7oe.41071$_r1.1290860@news20.bellglobal.com>, "Richard Lees"
    > <r_lees001@hotmail.com> wrote:
    >
    >> Slightly off-topic, but relevant to many - I hope.
    >>
    >> I have a power supply that was given to me. The previous owner is
    >> suspicious that it may be the cause of all his PC woes (hence the free
    >> gift)
    >> How do I go about testing it to see if it is OK in regards to correct
    >> voltages.
    >>
    >> It's laying on my desk at the moment. Do I have to install it in a case
    >> to
    >> test it, or can I test it 'on the bench'?
    >> What exactly am I looking for anyway?
    >> The 20 pin connector has many colored wires, Are the colours
    >> significant?
    >> How do I test for 12, 5 and 3 volts??
    >>
    >> Sorry for the newbie-like question, but It would be a shame to throw it
    >> in
    >> the garbage without checking it out first.
    >>
    >> Many thanks
    >> Richard
    >
    > Pinout is on page 19:
    > http://www.formfactors.org/developer/specs/atx/atx2_1.pdf
    >
    > (pin 1) (pin 11)
    > +3.3VDC +3.3VDC
    > +3.3VDC -12VDC
    > COM COM
    > +5VDC PS_ON# <--- connect to COM to start PSU.
    > COM COM <--- Plastic lock latch is
    > +5VDC COM <--- next to these pins.
    > COM COM
    > PWR_OK -5VDC
    > +5VSB +5VDC
    > +12VDC +5VDC
    >
    > You have six voltages to test:
    >
    > +5VSB - standby supply for sleeping computer, also powers start up
    > circuit on PSU. If not at full 5 volts, PSU may not work
    > properly, as supervisor cct in PSU will not be properly powered.
    > For the PSU to be completely turned off, PS_ON# should float
    > near the same +5VSB voltage. When PS_ON# is grounded (to COM),
    > the supply runs.
    > +3.3VDC - Used by PCI/AGP cards for chip power. May be used for
    > memory power, via linear regulation.
    > +5VDC - Used to power Vcore switching regulator on Asus AthlonXP boards.
    > Video card power, disk drive power.
    > +12VDC - Used to power Vcore switching regulator on P4/Athlon64 boards.
    > Video card power, disk drive power.
    > -5V - Historically, used for ECL or really old tech, three rail
    > DRAM memories. Maybe some kind of video card RAMDAC.
    > Typically not used today. Possibly used in linear (op amp)
    > circuits.
    > -12V - On Asus boards, can be used for RS-232 converter chip. Also
    > potentially used for op amps in linear regulators. It is hard
    > to say which negative rail Asus would use on their op-amp
    > circuits, as negative swings are not really required. In any
    > case 0.1 amps of consumption on a motherboard is probably
    > a reasonable estimate.
    >
    > A quick test, is to connect PS_ON# to a COM pin. The plastic lock
    > latch will help guide you to the right cluster of pins. The purpose
    > of a quick test, is just to check that the PSU fan starts to spin.
    > That would only prove that the supervisory circuit is capable of
    > turning on, in a situation where, say, a motherboard refuses to start.
    >
    > To quantify operation, you need a load on the PSU. One choice
    > is to apply the minimum load necessary for proper regulation.
    > Some supplies have minimum current loads specified on the label
    > on the side of the supply. If you draw that minimum current, then
    > the output is guaranteed to be within 5% of the proper voltage.
    > One would hope, under those conditions, it is a lot closer than
    > that.
    >
    > To measure the output, you will need a voltmeter. Home units are
    > typically not that good, and my $100 CDN meter is good to about
    > 1.5% to 2% accuracy, depending on range used. That means there is
    > room for doubt in the readings, to those precentages.
    >
    > Drawing the minimum supply current ensures the outputs will be in
    > spec. A second test would be a load test, using a representative
    > load. Using a load like this, proves the power supply will be
    > able to run a real motherboard - the load circuit takes the risk
    > out of having to connect a real motherboard, to prove the power
    > supply works.
    >
    > Here are some representative loads measured on systems here:
    >
    > A7N8X (3200+) P4C800-E (2.8GHz)
    > 3 DIMMs 4 DIMMs
    > +3.3V 5.5A 13.75A
    > +5.0V 16 + 5.5A 0.6 + 5.5A
    > +12.0V 0.5 + 0.9A 6.4 + 0.9A
    >
    > The added currents shown above (5.5A and 0.9A) are for a 9800pro
    > AGP video card while gaming. The 6.4A for the P4, is 6 amps for the
    > processor and 0.4A for the processor fan.
    >
    > To build a load tester, you will need a cable harness (snip up
    > a 20 to 24 pin adapter cable - even a 24 pin connector can be
    > used for the project, as there is only one way to plug a 20 pin
    > power supply into such a connector, and have all the pins
    > connected). You will also need resistors.
    >
    > To work out a load resistance:
    >
    > V/I = R_load = 3.3V/5.5A = 0.6 ohms
    >
    > V*I = power_dissipation = 3.3V*5.5A = 18.15 watts
    > Can also be calculated as V*V/R, if only V and R are known.
    >
    > More than one resistor can be used to build a load. Two 0.3 ohm
    > resistors put in series, would give a 0.6 ohm load. Two 1.2 ohm
    > resistors put in parallel, would give a 0.6 ohm load. The
    > power dissipated in each case, is now split between the two
    > resistors, so two smaller resistors can be used to make a larger
    > resistor. In the third example below, a square matrix of resistors
    > of equal value, can be used. In that case, each resistor only
    > needs to handle 1/9th of the total power to be dissipated.
    >
    > ----- 0.3 ------ 0.3 ------ = 0.6 ohms
    >
    > ---+--- 1.2 ---+--- = 0.6 ohms = R1*R2/(R1+R2)
    > | |
    > +--- 1.2 ---+
    >
    > ----+--- 0.6 ---+--- 0.6 ---+--- 0.6 ---+----- = 0.6 ohms
    > | |
    > +--- 0.6 ---+--- 0.6 ---+--- 0.6 ---+
    > | |
    > +--- 0.6 ---+--- 0.6 ---+--- 0.6 ---+
    >
    > (Hint - the parallel configuration may be easier to construct
    > - a ladder constructed of stiff copper house wiring
    > could be used to mount resistors in parallel.)
    >
    > There are many styles of power resistors. In the two examples
    > below, one is designed for free-standing operation. The other
    > one is intended for use with a heat sink (but no thermal data
    > is given?). In the load examples in the table above, the 5V
    > at 21.5 amp load would be the hardest one to cool, at 108 watts.
    > For some resistors I've been looking at, they appear to be
    > intended to dissipate the rated power without forced air, but
    > if you run a fan over them, you might not burn yourself on
    > them.
    >
    > There are some candidate resistors here. To reach our target
    > resistances using these products, in some cases, multiple
    > resistors are needed (in parallel) to get the resistance low
    > enough. In other cases, multiple resistors are needed to get
    > enough power handling capability. As the Digikey catalog
    > doesn't have all possible resistor values, sometimes a higher
    > power resistor must be substituted to get a necessary resistor
    > value. (I.e. The selection process is a mess. I did all the
    > math necessary, to build my load box, while standing in front
    > of the power resistor display rack at my local electronics
    > store. That is because you never know what resistors will be
    > in stock...)
    >
    > FVT series: The FVT are fixed value resistors. Vitreous enamel
    > looks to be a high temperature material, so you can burn the
    > hell out of these.
    >
    > http://dkc3.digikey.com/PDF/T052/1075.pdf
    >
    > The TMC ones (second item from top of page) have a casing suitable
    > for use with a heatsink. Now, there simply isn't enough data
    > here, to design with these and understand what you are doing.
    > (No thermal resistance data, for example.) How many of these
    > could you bolt to one heatsink ?
    >
    > http://dkc3.digikey.com/PDF/T052/1076.pdf
    > ==> http://www.heiresistors.com/aluminum.htm
    >
    > A7N8X (3200+) P4C800-E (2.8GHz)
    > 3 DIMMs 4 DIMMs
    > +3.3V 5.5A => 0.6ohm 18W 13.75A => 0.24ohm 45W
    > +5.0V 21.5A => 0.23ohm 108W 6.1A => 0.82ohm 31W
    > +12.0V 1.4A => 8.6ohm 17W 7.3A => 1.64ohm 88W
    > totals 143W 164W
    >
    > now select some resistor combinations...
    >
    > A7N8X (3200+) P4C800-E (2.8GHz)
    > 3 DIMMs 4 DIMMs
    > +3.3V 5.5A => 0.6ohm 18W 13.75A => 0.24ohm 45W
    > (3) FVT25-2.0-ND in (4) FVT50-1.0-ND in
    > parallel $9.93 parallel $19.16
    >
    > +5.0V 21.5A => 0.23ohm 108W 6.1A => 0.82ohm 31W
    > (4) FVT50-1.0-ND in (1) FVT50-1.0-ND parallel with
    > parallel $19.16 (1) FVT50-5.0-ND $9.58
    >
    > +12.0V 1.4A => 8.6ohm 17W 7.3A => 1.64ohm 88W
    > (1) FVT25-10-ND $3.28 (1) FVT100-2.0-ND parallel with
    > (1) FVT25-10-ND $11.49
    >
    > -5V (1) FVT25-25-ND $3.28 (1) FVT25-25-ND $3.28
    > will draw 0.2 amps will draw 0.2 amps
    >
    > -12V (1) FVT50-50-ND $4.50 (1) FVT50-50-ND $4.50
    > will draw 0.24 amps will draw 0.24 amps
    >
    > +5VSB (1) FVT25-10-ND $3.28 (1) FVT25-10-ND $3.28
    > will draw 0.5 amps will draw 0.5 amps
    >
    > Total $43 for resistors $51 for resistors
    > + 80mm fan for cooling 80mm fan for cooling
    >
    > Wiring the A7N8X example:
    >
    > +3.3 ----+----+----+
    > | | |
    > 2ohm 2ohm 2ohm
    > | | |
    > COM ----+----+----+
    >
    > +5.0 ----+----+----+----+
    > | | | |
    > 1ohm 1ohm 1ohm 1ohm
    > | | | |
    > COM ----+----+----+----+
    >
    > +12.0 ----+-----------+
    > | | (red)
    > 10ohm 80mm fan
    > | | (black)
    > COM ----+-----------+
    >
    > -5V ----+
    > |
    > 25ohm
    > |
    > COM ----+
    >
    > -12V ----+
    > |
    > 50ohm
    > |
    > COM ----+
    >
    > +5VSB ----+ PS_ON+ ----+
    > | |
    > 10ohm (toggle switch)
    > | |
    > COM ----+ COM ----+
    >
    > Note: This is just to give you some ideas for how to construct
    > your own PSU load box. If you can find cheaper resistors, you
    > will be able to use more of them, and perhaps have them run a
    > bit cooler. The FVT100-2.0-ND resistor on the right hand example
    > is going to get pretty hot. When using the 80mm fan, it might
    > be a good idea to build a "wind tunnel" with sheet metal, to
    > shape the airflow around the resistors.
    >
    > You will also want some place to probe with your volt meter.
    > So, if building vertical ladders with copper wire, screwed down
    > to a wooden base, leave enough excess wire on the ends of the
    > ladder, so you can probe with the voltmeter.
    >
    > When testing the PSU, run it with the representative load for
    > a couple of hours, and see if all voltages are still within
    > 5% of the stated values.
    >
    > There is no point testing the "full power" rating of the
    > supply, because many commonly available power supplies will
    > disappear in a cloud of smoke if you do that. The idea of a
    > load test, is to present a representative load, similar to
    > the motherboard you will be using.
    >
    > The power supply test products that have LED indicators on
    > them, could be using a window comparitor circuit. For example,
    > if one analog comparator checks for 11.4V, and another one checks
    > for 12.6V, using some logic gates, those comparators can be
    > used to check that the voltage is within the "window" of
    > 11.4V <= V_out <= 12.6V. Under those conditions, the LED comes
    > on. If the voltage is outside the window, the LED goes off.
    > You can get the same information by simply measuring the output
    > with a voltmeter.
    >
    > P.S. I'm not responsible if you burn yourself on the resistors!
    > They can get really hot (resistors rated to 350C degrees), so
    > don't be poking them with your fingers. As long as there is a
    > decent airflow with the cooling fan, that should prevent them
    > from getting all the way to 350C. Make sure there is some
    > separation between the resistor and any combustable material.
    > Using bare copper wire to hook up the resistors will avoid
    > the embarrassment of having the wire insulation start to burn.
    > And, above all, don't run this gadget unattended - turn it off
    > and unplug it, if you leave the room. Think of having to explain
    > to the insurance agent about power supply testers :-)
    >
    > Is it worth $100 for test gear (tester+voltmeter), to test a
    > $30 power supply ? Only you can answer that. I built my tester,
    > just to make sure I don't kill any expensive motherboards. My
    > tester draws less current than the examples above.
    >
    > Have fun,
    > Paul
  4. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    If it is NOT a name brand High Quality power supply unit, I would save
    yourself a lot of time and grief and toss it.

    --
    DaveW


    "Richard Lees" <r_lees001@hotmail.com> wrote in message
    news:ON7oe.41071$_r1.1290860@news20.bellglobal.com...
    > Slightly off-topic, but relevant to many - I hope.
    >
    > I have a power supply that was given to me. The previous owner is
    > suspicious that it may be the cause of all his PC woes (hence the free
    > gift)
    > How do I go about testing it to see if it is OK in regards to correct
    > voltages.
    >
    > It's laying on my desk at the moment. Do I have to install it in a case
    > to test it, or can I test it 'on the bench'?
    > What exactly am I looking for anyway?
    > The 20 pin connector has many colored wires, Are the colours significant?
    > How do I test for 12, 5 and 3 volts??
    >
    > Sorry for the newbie-like question, but It would be a shame to throw it in
    > the garbage without checking it out first.
    >
    > Many thanks
    > Richard
    >
    >
    >
    >
    >
  5. Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

    It's an Antec 400 watt.
    Fairly new, Can't be shipped back under warranty because previous owner
    thoght "the fuse had blown inside" and broke the seal when he opened it up!

    Richard L


    "DaveW" <none@zero.org> wrote in message
    news:R_CdndZO0qo0qj_fRVn-2w@comcast.com...
    > If it is NOT a name brand High Quality power supply unit, I would save
    > yourself a lot of time and grief and toss it.
    >
    > --
    > DaveW
    >
    >
    >
    > "Richard Lees" <r_lees001@hotmail.com> wrote in message
    > news:ON7oe.41071$_r1.1290860@news20.bellglobal.com...
    >> Slightly off-topic, but relevant to many - I hope.
    >>
    >> I have a power supply that was given to me. The previous owner is
    >> suspicious that it may be the cause of all his PC woes (hence the free
    >> gift)
    >> How do I go about testing it to see if it is OK in regards to correct
    >> voltages.
    >>
    >> It's laying on my desk at the moment. Do I have to install it in a case
    >> to test it, or can I test it 'on the bench'?
    >> What exactly am I looking for anyway?
    >> The 20 pin connector has many colored wires, Are the colours
    >> significant?
    >> How do I test for 12, 5 and 3 volts??
    >>
    >> Sorry for the newbie-like question, but It would be a shame to throw it
    >> in the garbage without checking it out first.
    >>
    >> Many thanks
    >> Richard
    >>
    >>
    >>
    >>
    >>
    >
    >
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