Hi Paul;
Thanks for your prompt response!
I closed the power pins for a very short time with a jumper--I am aware
that this is a momentary connection.
Now, green led means that your +5.0V is fine (as verfified also with a
voltmeter) Once I close the PWR pins I get absolutely NADA! No fans,
nothing. Therefore I cannot determine if the power supply +/- 12.0V,
-5.0V, etc, is faulty, or if the motherboard stopped sensing my PWR to
tell my P/S to enable the rest of the power rails.
I will get a new and stronger P/S, remove each card (video, sound,
SCSI, etc) and try it like that.
I don't think is the CPU, though--what do you think?
Thanks;
Yes, the green LED means the +5VSB is fine. But the +5VSB must be
steady - the green LED cannot flicker or flash. If the green LED
will not stay lit, every time the green LED goes off, so will the
main power of the supply.
Unless you can remember a specific event, where you did something
that could potentially have damaged the motherboard (like drop a
screwdriver on it, and scrape a tiny component off the motherboard),
then it is generally safe to assume the motherboard is able to
detect the momentary closure of the two PWR pins. There can be
situations, if for example, an IDE cable is only partially seated
in a motherboard IDE connector, where you'll discover the
motherboard no longer behaves normally. But if all cables haven't
been disturbed lately, and you've checked that everything is plugged
in where it is supposed to be, then a failure to start likely
means the PSU has died.
To eliminate a short of the motherboard to something, you can
do the cardboard test. You can remove the motherboard and PSU
from the chassis, and assemble them on your work table. You don't
need anything connected to the PANEL header. Plug the PSU into
the motherboard, then plug the PSU into the wall. You should be
able to momentarily touch the two PWR switch pins on the PANEL
header with a screwdriver tip, and start the board. If that
doesn't work, then I would try another power supply first. And,
if it happens not to be the power supply that has failed this
time, rest assured, you'll get to use the replacement power
supply sometime in the next couple of years anyway. (Fan
failure, capacitor failure, lightning etc.)
As you note, the "AGP warn" circuit can prevent the PWR switch
from starting the board. AFAIK, the red LED would light, if
that circuit got upset for any reason. I think "AGP warn" is
disabled, if the AGP video card is removed from the motherboard,
and there must be a pin on the video card slot that is used to
detect the presence of an AGP video card and enable the circuit.
It is possible for the "AGP warn" circuit to fail, but generally
what happens, is the red LED stays on all the time, and the
board won't start. If your red LED is off, it would take a double
failure ("AGP warn" fails and red LED fails too) to kill the
board, and that is too unlikely to contemplate. If a motherboard
survives the first week of continuous use, chances are it will
have a long life, barring a "finger problem" of some sort.
Paul
