Power Supply Problem

  • Thread starter Thread starter Najam.ITEngineer
  • Start date Start date
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Najam.ITEngineer

Dear All,
My machine never starts in one go. you have to unplug the power plug
from the power supply or sometimes switch off the main power. I do this
2-3 times then my machine starts and remain on until I wish. The
machine doesn't start at all...only the processor heat sink fan moves a
little bit and then stops...the computer only starts when the post
light blinks on the keyboard when you switch on the power, if there is
no light then it will not start..is it some kind of earth problem with
the power supply / motherboard? I've changed the power supply, but it
doesn't seems to be the problem...please advise...thanks
 
Dear All,
My machine never starts in one go. you have to unplug the power plug
from the power supply or sometimes switch off the main power. I do this
2-3 times then my machine starts and remain on until I wish. The
machine doesn't start at all...only the processor heat sink fan moves a
little bit and then stops...the computer only starts when the post
light blinks on the keyboard when you switch on the power, if there is
no light then it will not start..is it some kind of earth problem with
the power supply / motherboard? I've changed the power supply, but it
doesn't seems to be the problem...please advise...thanks
Click to expand...

Sounds like a bad motherboard. The power supply must send a power_OK signal
to the mainboard, which passes it to the CPU. Then the CPU can wake up and
run POST. As you've already switched the power supply, that would seem to
indicate that the mainboard still thinks that the power is not good. The
motherboard could be shorted to something (underneath), or it could just be
a bad mainboard. -Dave
 
how old is this machine/mainboard?

sounds like the PSU, you said you changed it what did you replace it with?
 
My machine never starts in one go. you have to unplug the power plug
from the power supply or sometimes switch off the main power. I do
this 2-3 times then my machine starts and remain on until I wish. The
machine doesn't start at all...only the processor heat sink fan moves
a little bit and then stops...the computer only starts when the post
light blinks on the keyboard when you switch on the power, if there is
no light then it will not start..is it some kind of earth problem with
the power supply / motherboard? I've changed the power supply,
but it doesn't seems to be the problem...please advise...thanks
Click to expand...

Its almost certainly a bad motherboard, may well be bad caps on the motherboard.

Unplugging the power supply drops the +5VSB standby voltage to
the motherboard and sees the keyboard led go out, so its sometimes
resetting the motherboard when its plugged in again, but not always.

If its always been like that, it never did start properly without that
farting around, it may well be that the power supplys cant provide
enough standby power. But thats unlikely unless both of the power
supplys you tried were on the puny end of power supplys and are identical.
 
Yep. Same as the other guy. You have bad
electrolytics in the start circuit of both psupplies.
Getting to be fairly common, and just showing
up this year. Bad capacitors out there. Rest of
the supply is working. That is why the fans
and such are coming up.

johns
 
for what it's worth...
I fixed one once with the same symtoms by going into the bios and setting it
on "use best settings" or "use default settings." I forget which, but one
of them cured it.

Mike
 
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