Power Supply Tester


R

RF

All,

I have been working on this pc, (Dell Dimension 2300 2 GHz, 256 MB, 40 GB),
and despite being only 2 - 3 years old, the inside was filthy. I cleaned it
out very well with compressed air, afterward, it would not start, and in
fact, would turn slightly( the fans would move), just by plugging it in.
After I took it apart and re-cleaned everything, I was able to get the pc to
turn on normally. I reimaged, and everything appears to be fine, However,
today I borrowed a power supply tester, and when I tested it, one of the 5
volt lights does not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on.
Does this mean that the power supply is bad? The computer seems to be
running fine now.


RF
 
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M

Mark

Could be getting ready to go....I would leave it on for a long time and see
if it starts rebooting.
 
R

RF

A side note, this is a P4 power supply. I don't know if that makes a
difference or not.

Thanks,

RF
 
D

Danny Kile

RF said:
All,

I have been working on this pc, (Dell Dimension 2300 2 GHz, 256 MB, 40 GB),
and despite being only 2 - 3 years old, the inside was filthy. I cleaned it
out very well with compressed air, afterward, it would not start, and in
fact, would turn slightly( the fans would move), just by plugging it in.
After I took it apart and re-cleaned everything, I was able to get the pc to
turn on normally. I reimaged, and everything appears to be fine, However,
today I borrowed a power supply tester, and when I tested it, one of the 5
volt lights does not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on.
Does this mean that the power supply is bad? The computer seems to be
running fine now.


RF
The tester is more that likely for standard AT or ATX type power
supplies, however, Dell uses a proprietary power supply and the pin outs
would be different.

--
Danny Kile
Please reply to the Newsgroup ONLY

"Dogs come when they're called, CATS take a message and get back to
you." Mary Bly
 
R

Ralph Wade Phillips

Howdy!

RF said:
All,

I have been working on this pc, (Dell Dimension 2300 2 GHz, 256 MB, 40 GB),
and despite being only 2 - 3 years old, the inside was filthy. I cleaned it
out very well with compressed air, afterward, it would not start, and in
fact, would turn slightly( the fans would move), just by plugging it in.
After I took it apart and re-cleaned everything, I was able to get the pc to
turn on normally. I reimaged, and everything appears to be fine, However,
today I borrowed a power supply tester, and when I tested it, one of the 5
volt lights does not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on.
Does this mean that the power supply is bad? The computer seems to be
running fine now.

I'd cross check - certain Dells use a non-standard wiring for the
ATX power supply, and such will require an adapter for most ATX testers to
work properly.

RwP
 
R

ric

RF said:
I have been working on this pc, (Dell Dimension 2300 2 GHz, 256 MB, 40 GB),
and despite being only 2 - 3 years old, the inside was filthy. I cleaned it
out very well with compressed air, afterward, it would not start, and in
fact, would turn slightly( the fans would move), just by plugging it in.
After I took it apart and re-cleaned everything, I was able to get the pc to
turn on normally. I reimaged, and everything appears to be fine, However,
today I borrowed a power supply tester, and when I tested it, one of the 5
volt lights does not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on.
Does this mean that the power supply is bad? The computer seems to be
running fine now.

The need for a -5v output on the PSU was removed from the ATX specification
in April, 2003. (ver 1.3)

http://www.formfactors.org/developer\specs\ATX12V PSDG2.01.pdf
 
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K

kony

All,

I have been working on this pc, (Dell Dimension 2300 2 GHz, 256 MB, 40 GB),
and despite being only 2 - 3 years old, the inside was filthy. I cleaned it
out very well with compressed air, afterward, it would not start, and in
fact, would turn slightly( the fans would move), just by plugging it in.
After I took it apart and re-cleaned everything, I was able to get the pc to
turn on normally. I reimaged, and everything appears to be fine, However,
today I borrowed a power supply tester, and when I tested it, one of the 5
volt lights does not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on.
Does this mean that the power supply is bad? The computer seems to be
running fine now.

-5V is irrelevant for a semi-modern PC, that voltage is "often"
still implemented on an ATX only due to spec, "true"
compatibility with some odd design never seen in typical PC. On
a Dell or any typical system not using -5V, you can completely
remove -5V line and expect no problem, other than a hardware
monitor type warning "if" that voltage is monitored at all. When
a system does not use any particular voltage rail, it is common
for that rail to be out of spec since there is no load on it,
unless the power supply itself has a built-in load, which isn't
to be expected on that rail.

Perhaps a more important question is, if everthing appears fine,
why the further testing?
 
C

Conor

today I borrowed a power supply tester, and when I tested it, one of the 5
volt lights does not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on.
Does this mean that the power supply is bad? The computer seems to be
running fine now.
-5V is no longer used.
 
L

larrymoencurly

RF said:
I have been working on this pc, (Dell Dimension 2300 2 GHz,
256 MB, 40 GB), and despite being only 2 - 3 years old, the
inside was filthy. I cleaned it out very well with compressed
air, afterward, it would not start, and in fact, would turn
slightly (the fans would move), just by plugging it in.
After I took it apart and re-cleaned everything, I was able
to get the pc to turn on normally. I reimaged, and everything
appears to be fine, However, today I borrowed a power supply
tester, and when I tested it, one of the 5 volt lights does
not come on, (the - 5V), and overall, both the "good" light
and the 'danger' light come on. Does this mean that the
power supply is bad? The computer seems to be running fine now.

I have a couple of mobos made in 1997 that don't use the -5V or -12V,
so I wouldn't worry about that. But I also wouldn't trust any PSU
tester because one I borrowed said that a PSU was OK even though its
+12V rail was at about 10.5V and kept the HD from spinning. It's
better to buy a cheap digital multimeter and learn how to use it
because not only will it be a lot more accurate (2% error, worst
case), but it can be used for testing lots of other things.
 
M

Michael

larrymoencurly said:
I have a couple of mobos made in 1997 that don't use the -5V or -12V,
so I wouldn't worry about that. But I also wouldn't trust any PSU
tester because one I borrowed said that a PSU was OK even though its
+12V rail was at about 10.5V and kept the HD from spinning. It's
better to buy a cheap digital multimeter and learn how to use it
because not only will it be a lot more accurate (2% error, worst
case), but it can be used for testing lots of other things.

Yeah I second that. A cheap tester can be $9 on sale at Radio Shack,
and blows the doors off a single-purpose tester. Even a nice meter can
be had for $40, or you can blow a week's salary on a Fluke if you like.
Having R, V, and I testing is nice, although I like capacitance
testing too. Now my question is, does the single-purpose tester put the
voltage source under load? It's possible for a supply to do well under
no load, and drop miserably under load. No supply on the planet is an
ideal voltage source.

I wonder why - 5 V is more rare? Either the - 5 V is derived from some
onboard regulator, or it's not needed. And 5 V is more for TTL, so
perhaps that's been superceded by other topologies.

michael
 
D

David Maynard

Michael said:
Yeah I second that. A cheap tester can be $9 on sale at Radio Shack,
and blows the doors off a single-purpose tester. Even a nice meter can
be had for $40, or you can blow a week's salary on a Fluke if you like.
Having R, V, and I testing is nice, although I like capacitance testing
too. Now my question is, does the single-purpose tester put the voltage
source under load? It's possible for a supply to do well under no load,
and drop miserably under load. No supply on the planet is an ideal
voltage source.

I wonder why - 5 V is more rare? Either the - 5 V is derived from some
onboard regulator, or it's not needed.

It's no longer needed. Was there for older technology that needed a
negative BIAS source.
 
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M

Michael

Franc said:
I doubt it. The -12V rail would be needed for RS232.

In my audio tinkering, I often used LM series regulators to lower the
voltage from my PS. A lot of electronics does this in one form or
another, as one size usually doesn't fit all. There are single-chip
inversion solutions as well, although it's probably easier to start with
a decent negative rail than generate one after the fact.

michael
 
K

kony

I doubt it. The -12V rail would be needed for RS232.


- Franc Zabkar

What year would you consider to be the *average* transition point
towards serial drivers not needing -12V? I do think the typical
chips from National and TI still did at beginning of '97, but
don't know after that.
 
R

RF

Guys,

Thank you so much for your input. These newsgroups never cease to amaze me
with their knowledge base.

RF
 
L

LadyTech

larrymoencurly said:
I have a couple of mobos made in 1997 that don't use the -5V or -12V,
so I wouldn't worry about that. But I also wouldn't trust any PSU
tester because one I borrowed said that a PSU was OK even though its
+12V rail was at about 10.5V and kept the HD from spinning. It's
better to buy a cheap digital multimeter and learn how to use it
because not only will it be a lot more accurate (2% error, worst
case), but it can be used for testing lots of other things.

I have to agree. I have a PSU tester and it tested a PSU as okay, but
the PSU was faulty... I learned to use my digital multimeter from now
on :)
 
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M

Michael

LadyTech said:
I have to agree. I have a PSU tester and it tested a PSU as okay, but
the PSU was faulty... I learned to use my digital multimeter from now
on :)

Based on the anecdotal evidence, I'd guess that some testers are only
checking for any voltage on a specified "pin," rather than precisely
measuring it, else a false positive with 1.5 V undervoltage would be
unlikely. If the tester is like $10 to $15 I can understand that, any
more and it should do precise testing, given that a $9 DMM can do the same.

michael
 
L

larrymoencurly

Franc Zabkar said:
-12V,

I doubt it. The -12V rail would be needed for RS232.

One is a 430TX mobo made by some defunct company and doesn't seem to
have any documentation available for it on the web. The other is an
FIC PA-2007 (VIA VP2 chipset) that uses a 5V-only Analog Devices brand
chip to convert between RS-232 and TTL levels and contains its own
charge pump circuitry to generate +10V and -10V for the RS-232 side.
When I bought this mobo used, its RS-232 ports didn't work except at
slow speeds because two .1 uF surface mount capacitors for the charge
pump were missing. I thought they'd been knocked off during
installation of a PCI card, but apparently they had vaporized when the
previous owner plugged or unplugged a parallel printer or serial
device with the power on. I know that the parallel port could do this
because my friend later unplugged a printer from this mobo and caused
the same capacitors to explode.
 
L

larrymoencurly

Yeah I second that. A cheap tester can be $9 on sale at
Radio Shack, and blows the doors off a single-purpose
tester. Even a nice meter can be had for $40, or you can
blow a week's salary on a Fluke if you like.

I have a Fluke 73 that someone gave me in lieu of cash, and even
though it was their cheapest model it's built noticeably better than
my no-name, which has a 250V fuse for a 600V circuit (Fluke has a
jumbo 600V fuse wrapped in fiberglass cloth to prevent fragments from
flying out in case it explodes), and it's supposed to be able to run
2,000 hours on a single 9V battery, compared to just 250 hours for my
no-name.
Having R, V, and I testing is nice, although I like capacitance
testing too.

Also some meters, even inexpensive ones, now have an RS-232 serial
port and software to allow their readings to be monitored by a PC,
which can be useful for checking intermittent equipment. My no-name
has a feature that can do this by remembering the high and low values.
Now my question is, does the single-purpose tester put the
voltage source under load? It's possible for a supply to
do well under no load, and drop miserably under load. No
supply on the planet is an ideal voltage source.

The tester I borrowed has a pair of 5W load resistors for the +3.3V
and +5.0V.
5V through 5 ohms = 5W, and I learned the hard way that when a
resistor is run at its full power rating, it can melt plastic and burn
skin. Apparently, some other PSU testers are built the same way.
 
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