No Power!

[steve d. podleski]

While I was working on my pc, the system shut down as if the power failed.
I tried to turn the system back on but nothing happened. The only sign of
power was a green light on the motherboard. I replaced the power supply with
a used Dell power supply that I got at a surplus store; this used power
supply had an extra bundle of blue and while cable with a small connector
that, I guess, needs to be connected to the motherboard but I could not find
a compabatible socket; the old power supply had only one connector to the
motherboard.This replacement power supply had no effect including not
lighting the green light on the motherboard.

Also, when the computer was functional, I would get occasional warnings
from the BIOS that the fan had 0 rpms but the after a few seconds, the fan
rpm was back to full value; I did not see this warning before the compuer
shut down.

This system is over 5 years old with a 1.1GHz Athlon, ASUS motherboard and
300W power supply and 768MB Crucials (sp?) RAM.

Any ideas?

 

[Arno Wagner]

While I was working on my pc, the system shut down as if the power failed.
I tried to turn the system back on but nothing happened. The only sign of
power was a green light on the motherboard. I replaced the power supply with
a used Dell power supply that I got at a surplus store; this used power
supply had an extra bundle of blue and while cable with a small connector
that, I guess, needs to be connected to the motherboard but I could not find
a compabatible socket; the old power supply had only one connector to the
motherboard.This replacement power supply had no effect including not
lighting the green light on the motherboard.

Bad idea to try a custom PSU. In the worst case you could completely
fry your system, because they might use a different connector layout.
As with the extra wires: How do you know they are not the +12v 50A
extra power line? If connected to a power-putton input, what you
hear will be the "pop" when the chipset explodes....

Also, when the computer was functional, I would get occasional warnings
from the BIOS that the fan had 0 rpms but the after a few seconds, the fan
rpm was back to full value; I did not see this warning before the compuer
shut down.

Typical for a fan with bearing trouble.

This system is over 5 years old with a 1.1GHz Athlon, ASUS motherboard and
300W power supply and 768MB Crucials (sp?) RAM.

Get a known-to be good PSU and try that. Check all fans. If the
CPU fan stopped, the CPU may be fried.

Arno

 

[steve d. podleski]

Arno.

Thanks for helping.

How can I tell if the PSU fan is bad without having the PSU installed?

 

[Arno Wagner]

Arno.

Thanks for helping.

How can I tell if the PSU fan is bad without having the PSU installed?

Actually I meant the CPU fan. Or do you monitor the PSU fan as well?
It would require a special fan-like cable from the PSU to the maniboard.

If you really want to test the PSU fan. easiest is to switch it
on. For that you need to connect the -pwr line and GND. A guide
with photos is here:
http://www.rojakpot.com/showarticle.aspx?artno=268&pgno=0
If the fan does not spin after this, it is broken.

Arno

 

[Paul]

Arno.

Thanks for helping.

How can I tell if the PSU fan is bad without having the PSU installed?

The fan monitor has a "minimum RPM" value. When the RPMs
drop below the minimum value, the readout goes to zero.

I have a motherboard, where the minimum measurable value is
1800RPM. If the fan spins at 1801 RPM, the readout says 1801.
If the fan spins at 1799, the readout says 0. Your minimum
could be different than this.

This problem is caused by a counter overflow in the monitor chip.
There is a divider in the monitor chip, that can be adjusted, so
that lower fan RPM values can be read. A program like Speedfan
from almico.com may be able to make the lower fan values readable.
(At least, up to the limits of the adjustment in the monitor chip.)

The motherboard BIOS seems to be ill equipped to set this up
properly. The motherboard BIOS can set the threshold quite high.
Speedfan uses an autoranging algorithm, where the monitor chip
is adjusted down, until a value can be seen. If the fan *is*
actually zero, this can still be detected. When the monitor
is dialled as low as possible, it can still properly read out
a zero RPM fan as being zero.

A PSU can be tested, by connecting PS_ON# to COM. It is best to
have a small amount of load on the PSU, so that it can regulate
properly. An old disk drive, for example, draws 5V @ 1A and 12V @ 0.5A
and is better than nothing, as a dummy load. When PS_ON# is connected
to an adjacent COM pin, the fan will start to spin. If the fan
doesn't spin, you'd need a multimeter to figure out what is working
or not working. (The supervisor voltage on the PSU, is called +5VSB.
The power supply cannot run the rest of the outputs, unless the +5VSB
is operating first. If the +5VSB fails or is overloaded, there is
no chance of the other voltages being generated.)

Watch it with the old Dell supplies! They can fry an ordinary computer.
Especially if they have that "extra" connector. Look for Dell pinouts
on the web for more details, before using one.

Paul

 

[paulmd]

While I was working on my pc, the system shut down as if the power failed.
I tried to turn the system back on but nothing happened. The only sign of
power was a green light on the motherboard. I replaced the power supply with
a used Dell power supply that I got at a surplus store; this used power
supply had an extra bundle of blue and while cable with a small connector
that, I guess, needs to be connected to the motherboard but I could not find
a compabatible socket; the old power supply had only one connector to the
motherboard.This replacement power supply had no effect including not
lighting the green light on the motherboard.

Don't connect that if if your computer is not a Pentium 2 or Pentium 3
Dell! Not the same one. Wires are very different different.

If you're lucky, you can get the correct power supply for your
computer, and the motherboard will still work.

Also, when the computer was functional, I would get occasional warnings
from the BIOS that the fan had 0 rpms but the after a few seconds, the fan
rpm was back to full value; I did not see this warning before the compuer
shut down.

This system is over 5 years old with a 1.1GHz Athlon, ASUS motherboard and
300W power supply and 768MB Crucials (sp?) RAM.

Any ideas?

Get a standard ATX PSU, and try again.

 

[kony]

While I was working on my pc, the system shut down as if the power failed.

You were working on it while it was turned on ??!!

Could you describe what you "think" might have happened?
I suspect you might have shorted something, tripping the PSU
to shut off. That might mean you needed to unplug it from
the AC for a few minutes then retry it. If you didn't
unplug it from AC, it might not start.

I tried to turn the system back on but nothing happened. The only sign of
power was a green light on the motherboard. I replaced the power supply with
a used Dell power supply that I got at a surplus store; this used power
supply had an extra bundle of blue and while cable with a small connector
that, I guess, needs to be connected to the motherboard but I could not find
a compabatible socket;

What did that extra connector look like? I'd guess it's for
the PSU fan RPM sensor- and you don't need it, shouldn't
hook it up.

More important, does this Dell PSU's wiring colors and pin
positions match up to your other PSU? it might be a
proprietary, incompatible pinout.

the old power supply had only one connector to the
motherboard.This replacement power supply had no effect including not
lighting the green light on the motherboard.

Also, when the computer was functional, I would get occasional warnings
from the BIOS that the fan had 0 rpms but the after a few seconds, the fan
rpm was back to full value; I did not see this warning before the compuer
shut down.

It could mean the fan was bad, or it could just mean the fan
was running at a low RPM, low enough that the motherboard
bios couldn't detect it's RPM properly- that's a common bios
bug that is "Sometimes" corrected on later bios.

I'd plug the old PSU back into the system, try to start the
system and note whether it's fan is spinning (look at it,
not by the bios health monitor screen). If the fan isn't
spinning then turn the system off and decide whether to
attempt replacing the fan (if the PSU hadn't baked for too
long) or replacing whole PSU.

This system is over 5 years old with a 1.1GHz Athlon, ASUS motherboard and
300W power supply and 768MB Crucials (sp?) RAM.

Depends on exactly what happened when you were working on
it. if you think you damanged some particular part, pull
that part out. you might also unplug AC and clear CMOS,
then retry it.

 

[steve d. podleski]

You were working on it while it was turned on ??!!

Could you describe what you "think" might have happened?
I suspect you might have shorted something, tripping the PSU
to shut off. That might mean you needed to unplug it from
the AC for a few minutes then retry it. If you didn't
unplug it from AC, it might not start.

I think that I was typing when it shut off.

I unplugged the power cord and tried starting it without success.

What did that extra connector look like? I'd guess it's for
the PSU fan RPM sensor- and you don't need it, shouldn't
hook it up.

I need to look at it again.

More important, does this Dell PSU's wiring colors and pin
positions match up to your other PSU? it might be a
proprietary, incompatible pinout.

The Dell power supply had different colored wiring.

It could mean the fan was bad, or it could just mean the fan
was running at a low RPM, low enough that the motherboard
bios couldn't detect it's RPM properly- that's a common bios
bug that is "Sometimes" corrected on later bios.

I'd plug the old PSU back into the system, try to start the
system and note whether it's fan is spinning (look at it,
not by the bios health monitor screen). If the fan isn't
spinning then turn the system off and decide whether to
attempt replacing the fan (if the PSU hadn't baked for too
long) or replacing whole PSU.

I plugged the old PSU into the motherboard and did not connect anything
else. The fan did not run.
Will buy a new PSU.

Depends on exactly what happened when you were working on
it. if you think you damanged some particular part, pull
that part out. you might also unplug AC and clear CMOS,
then retry it.

How do you clear the CMOS?

 

[kony]

I think that I was typing when it shut off.

Oh, by working I'd thought you meant handling the hardware,
case open, etc.

The Dell power supply had different colored wiring.

Sometimes an OEM will substitute a different color, for
example blue for yellow (on the 12V leads), but it is
consistent, if one notes all the places these might've been
substituted, the pin positions remain the same as standard
ATX. Dell definitely did use some proprietarily wired PSU
though, it's quite possible that's what you have.

How do you clear the CMOS?

Unplug AC from PSU and either pull the battery for a few
minutes or use the clear CMOS jumper- either labeled on the
board or consult the manual for it's location.

 

[paulmd]

Oh, by working I'd thought you meant handling the hardware,
case open, etc.





Sometimes an OEM will substitute a different color, for
example blue for yellow (on the 12V leads), but it is
consistent, if one notes all the places these might've been
substituted, the pin positions remain the same as standard
ATX. Dell definitely did use some proprietarily wired PSU
though, it's quite possible that's what you have.

If the dell PSU has the 6 wire plug, with 3 blue, and 3 black or
white,. it's definitely the wrong PSU.

 

[steve podleski]

Bought a new PSU and voila, system powers up and boots.

Lucky to not have damaged the motherboard with my blunderings with the
surplus Dell PSU.

Thanks to all for their help!

 

[Arno Wagner]

Bought a new PSU and voila, system powers up and boots.
Congratulations.

Lucky to not have damaged the motherboard with my blunderings with the
surplus Dell PSU.

Indeed. Custom hardware sometimes is an accident waiting to happen...

Arno