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Diagnosing Power Supplies

 
 
Dave Hardenbrook
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      04-17-2005
Thanks to those who answered by question about mixing ATX and Micro-ATX
Power supplies and Mobo's. I have a few follow-up questions. When I
tested my client's MicroATX Mobo with a Full ATX Power supply, the Mobo
came to life on startup, which makes me suspect her Power Supply is
dead. However, this is the second Power Supply in a row that has died
on her in the last few months -- The current one I installed in
November. Is it probable that a new Power supply could tragically
drop dead so young?

I would like to use a multimeter to determine for certain, but I can
find no definitive guide for using one to test a Power Supply. Mike
Meyers goes into it in his A+ "All-in-One" guide, but he leaves out a
few details, like where the leads need to be plugged in on the
multimeter, whether the system needs to be powered on during the
test(!), and exactly what part of the wires on the connector the leads
need to be touching (do they have to be touching metal?). Armed with a
newly purchased $10.00 one from MicroCenter, I tried to follow his
instructions to the best of my ability, but registered zero, even when
testing a known working system, while it was powered up! I don't feel
confident enough about fiddling with electricity to proceed without
being absolutely certain of what I'm doing, so I'd appreciate some
guidance. (Could the *multimeter* be defective???)

Another clue in this mystery I'm struggling to interpret: My client
complains that her system had a hint of that "burnt rubber" smell in the
period between my installing the current Power Supply five months ago
and her system going dead this week, even though her system seemed to
work fine in that period. Could a faulty Power Supply have degraded her
Mobo to the point that it smelled burnt, but still functioned?
FWIW, I don;t detect what I'd descrive as a true "burnt" smell -- It has
only a faint, nondescript aroma such as I have detected on known working
Mobo's. Also, when I look at my client's Mobo, I see no sign of it
having been "cooked". But perhaps if I could successfully power it up
for a period, I would detect the "burning" smell my client describes.
Could defects in the last two Power supplies have resulted in a
"medium rare" Mobo that still works, possibly with degraded performance,
but not "well done" enough to fail outright, at least not *yet*...?

Final question: I have heard about faulty Power Supplies "killing"
Mobo's. Is the reverse possible, and that a subtle defect in my
client's Mobo could be "murdering" every Power Supply I connect it to?

Any insight the gurus can offer this young grasshopper would be greatly
appeciated.

--
Dave
 
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Dave Hardenbrook
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Posts: n/a
 
      04-17-2005
In article <Haw8e.4637$(E-Mail Removed)>, eelder1
@tampabay.rr.com says...
> At this point, a UPS may be in order. How many watts was the PS you
> replaced, rated at?


250W, which was the highest wattage I could find for a MicroATX PS.
Her previous one was 150W. And as it was she complained about the
higher-powered one being "too loud". Is a UPS or at least a really
decent Surge Suppressor the best solution?

--
Dave

 
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w_tom
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      04-18-2005
First lets eliminate those silly myths. Neither the UPS nor
a plug-in surge protector is a solution. Those are too often
promoted by myth purveyors that cannot even say (with numbers)
what those devices do.

More myths to confront. Reverse wires on AC receptacle will
not cause power supply failure. That outlet tester would be
wasted money. Anything that the outlet tester could report is
reported - and more - by the multimeter.

Another myth about ground rods - missing or existing -
would have nothing to do with power supply operation. Those
with basic electrical knowledge would know this.


Hopefully the multimeter is digital. If using an analog
meter, the readings will be insufficient. The meter should
have a ohms scale or conductivity measuring circuit. Put
meter in those modes and touch leads together. Meter should
read 0.

Now to determine what is coming out of power supply. Put
the meter in DC volts. Use this procedure to measure the
+5VSB (measure purple wire to black wire). This 5 volts
should exist when AC cord is connected AND when power supply
is both on and off. Procedures to use meter on a power supply
are described in two posts: "Computer doesnt start at all"
in alt.comp.hardware on 10 Jan 2004 at
http://tinyurl.com/2t69q and
"I think my power supply is dead" in alt.comp.hardware on 5
Feb 2004 at
http://tinyurl.com/yvbw9

A power supply properly constructed will never burn out
motherboards. The power supply must provide specs and must
specifically list over voltage protection. Furthermore, you
can short together all outputs from a power supply and that
supply still must not be damaged. Same applies to
motherboard. The motherboard also cannot damage a properly
constructed supply. But again, those supplies not provided
with a long list of numeric specs are often missing these and
many other standard and necessary functions.


Dave Hardenbrook wrote:
> Thanks to those who answered by question about mixing ATX and Micro-ATX
> Power supplies and Mobo's. I have a few follow-up questions. When I
> tested my client's MicroATX Mobo with a Full ATX Power supply, the Mobo
> came to life on startup, which makes me suspect her Power Supply is
> dead. However, this is the second Power Supply in a row that has died
> on her in the last few months -- The current one I installed in
> November. Is it probable that a new Power supply could tragically
> drop dead so young?
>
> I would like to use a multimeter to determine for certain, but I can
> find no definitive guide for using one to test a Power Supply. Mike
> Meyers goes into it in his A+ "All-in-One" guide, but he leaves out a
> few details, like where the leads need to be plugged in on the
> multimeter, whether the system needs to be powered on during the
> test(!), and exactly what part of the wires on the connector the leads
> need to be touching (do they have to be touching metal?). Armed with a
> newly purchased $10.00 one from MicroCenter, I tried to follow his
> instructions to the best of my ability, but registered zero, even when
> testing a known working system, while it was powered up! I don't feel
> confident enough about fiddling with electricity to proceed without
> being absolutely certain of what I'm doing, so I'd appreciate some
> guidance. (Could the *multimeter* be defective???)
>
> Another clue in this mystery I'm struggling to interpret: My client
> complains that her system had a hint of that "burnt rubber" smell in the
> period between my installing the current Power Supply five months ago
> and her system going dead this week, even though her system seemed to
> work fine in that period. Could a faulty Power Supply have degraded her
> Mobo to the point that it smelled burnt, but still functioned?
> FWIW, I don;t detect what I'd descrive as a true "burnt" smell -- It has
> only a faint, nondescript aroma such as I have detected on known working
> Mobo's. Also, when I look at my client's Mobo, I see no sign of it
> having been "cooked". But perhaps if I could successfully power it up
> for a period, I would detect the "burning" smell my client describes.
> Could defects in the last two Power supplies have resulted in a
> "medium rare" Mobo that still works, possibly with degraded performance,
> but not "well done" enough to fail outright, at least not *yet*...?
>
> Final question: I have heard about faulty Power Supplies "killing"
> Mobo's. Is the reverse possible, and that a subtle defect in my
> client's Mobo could be "murdering" every Power Supply I connect it to?
>
> Any insight the gurus can offer this young grasshopper would be greatly
> appeciated.

 
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