ATX power problem??

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Archived from groups: alt.comp.hardware.homebuilt (More info?)

Hi folks,

I recently had to replace my power supply and motherboard.
Everything has been fine for about 3 weeks but when i went to turn the
machine on yesterday it was 'dead', no power to anything.
Took the cover off thinking the PSU had gone again but found the power
light on the motherboard was lit and that the PSU was working fine.
Powered off the PSU, unplugged the main power cable, checked it, plugged
it back in again and when i powered up the PSU and pressed the on/off
switch on the case it powered up. I figured it was just a glitch and
left the PC on all day yesterday with no problems. Powered down the PC
using the shutdown command on windows but when i came to the machine
this morning it is dead again, ie. nothing happens when i press the
switch on the case. Unplugges the power cable and reconnected it again
and the system powers up fine.
ANY IDEAS???
Could it just be a dodgy on/off switch that is not triggering whatever
it has to trigger on the motherboard or is the motherboard faulty? What
does the handbook mean when it says that the switch puts the pc into a
'soft off' mode? i have only ever worked with PC's that had a proper
on/off power switch so i don't know exactly how this system works.
I'd be grateful of any advice before i go out and buy another mother
board if that is not the problem!!
Cheers,
John.

 

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Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 01 Mar 2005 10:20:35 +0000, "j.p"
<docbones5@yahoo.com> wrote:

>Hi folks,
>
>I recently had to replace my power supply and motherboard.
>Everything has been fine for about 3 weeks but when i went to turn the
>machine on yesterday it was 'dead', no power to anything.
>Took the cover off thinking the PSU had gone again but found the power
>light on the motherboard was lit and that the PSU was working fine.

Power light on mobo means there's power getting to it,
period. It doesn't mean anything is ok, just that enough
current is passing though to light an LED. BOTH the mobo
and the power supply could conceivably be ~ 80% dead
(unworkable) and the LED is lit.


>Powered off the PSU, unplugged the main power cable, checked it, plugged
>it back in again and when i powered up the PSU and pressed the on/off
>switch on the case it powered up. I figured it was just a glitch and
>left the PC on all day yesterday with no problems. Powered down the PC
>using the shutdown command on windows but when i came to the machine
>this morning it is dead again, ie. nothing happens when i press the
>switch on the case. Unplugges the power cable and reconnected it again
>and the system powers up fine.
>ANY IDEAS???

Power supply or battery


>Could it just be a dodgy on/off switch that is not triggering whatever
>it has to trigger on the motherboard or is the motherboard faulty?

Doubtful, but next time it does this you could simply remove
the side-panel, unplug the switch cable and short the two
pins together to rule that out.


>What
>does the handbook mean when it says that the switch puts the pc into a
>'soft off' mode? i have only ever worked with PC's that had a proper
>on/off power switch so i don't know exactly how this system works.
>I'd be grateful of any advice before i go out and buy another mother
>board if that is not the problem!!
>Cheers,
>John.

Handbooks (manual) is written by an individuals/company that
puts their own coloration on the info. Soft-off is called
"off" by some, S5 by others, it is the state seen when
system appears fully "off" but is still plugged into a live
AC outlet. Power supply is still supplying 5VSB power.

Check your motherboard to see if the PS2 and USB ports
(maybe more than one jumper(s) for the USB including the
pin-headers) are using 5V or 5VSB mode. Typically there is
a 3 pin jumper to chose one mode or the other. It is
possible your system has enough PS2 and/or USB devices
plugged in to exceed the 5VSB current capability of the
power supply. In which case you would want "5V", not 5VSB,
jumpered. Unless you had a LOT of devices attached it would
tend to suggest the power supply needs replaced, else you'd
need to keep as much as possible running from 5V, not 5VSB.

When you replaced the power supply, what did you get? If
it's a generic then you might just go ahead and replace it
again... after checking the battery voltage.