Motherboard dead? Light comes on but thats it

  • Thread starter Thread starter BertieBigBollox
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BertieBigBollox

Power LED on mobo comes on but nothing when you hit the power button.
Can I assume the mobo is dead?

Also, just to rule out a power button problem, is it acceptable to
short (with a jumper) the two-pin power button header on the mobo to
force a power on that way?
 
Power LED on mobo comes on but nothing when you hit the power button.
Can I assume the mobo is dead?

Also, just to rule out a power button problem, is it acceptable to
short (with a jumper) the two-pin power button header on the mobo to
force a power on that way?
Click to expand...
Prove the PSU first.
Yes to the second question.
 
Same result with a new PSU as well...

How would you test a PSU?
Click to expand...
A test meter from, say, Maplins.
That way you can test the PSU with it switched on (under load)
to see if it`s delivering the correct voltages.

As for the other supply you tried, was it adequate for the job ?.
 
A test meter from, say, Maplins.
That way you can test the PSU with it switched on (under load)
to see if it`s delivering the correct voltages.

As for the other supply you tried, was it adequate for the job ?.
Click to expand...

Initial PSU was a 250W Bestec, the new one is a 350W one...

Assuming the new one PSU is OK, would you assume the mobo is indeed
dead?
 
(e-mail address removed) "contributed" in 24hoursupport.helpdesk:
Same result with a new PSU as well...

How would you test a PSU?
Click to expand...

Stick your fingers in it and switch it on. If your hair starts pointing
towards the ceiling, the PSU is OK.
 
Initial PSU was a 250W Bestec, the new one is a 350W one...

Assuming the new one PSU is OK, would you assume the mobo is indeed
dead?
Click to expand...
You can`t `make assumptions` can you ?.
You need to Know you`re getting your correct voltages under load.
 
Initial PSU was a 250W Bestec, the new one is a 350W one...

Assuming the new one PSU is OK, would you assume the mobo is indeed
dead?
Click to expand...

No. Reseat all cards and memory. Try disconnecting or removing all unnecessary
items.
Google motherboard capacitors and look for pics of blown caps to see if that is
your problem.
 
You can`t `make assumptions` can you ?.
You need to Know you`re getting your correct voltages under load.
Click to expand...

OK. First PSU wont even power on with Pin 14 shorted - so thats
knackered for starters.
 
[email protected] said:
Power LED on mobo comes on but nothing when you hit the power button.
Can I assume the mobo is dead?

Also, just to rule out a power button problem, is it acceptable to
short (with a jumper) the two-pin power button header on the mobo to
force a power on that way?
Click to expand...

There is a green wire you can short to any black wire to power on the
PS.

Best to do this in place so the PS has a load, just use a paper clip
to short green and any black.
www.bluemax.net/techtips/ATXPowerSupplyWiring/ATXPowerSupplyWiring.htm
 
Power LED on mobo comes on but nothing when you hit the power button.
Can I assume the mobo is dead?

Also, just to rule out a power button problem, is it acceptable to
short (with a jumper) the two-pin power button header on the mobo to
force a power on that way?
Click to expand...

Whatever you do, don't take to a shop for repair paul!
 
Power LED on mobo comes on but nothing when you hit the power button.
Can I assume the mobo is dead?

Also, just to rule out a power button problem, is it acceptable to
short (with a jumper) the two-pin power button header on the mobo to
force a power on that way?
Click to expand...

Whatever you do, don't take to a shop for repair Paul!
 
BertieBigBollox wrote ...
OK. First PSU wont even power on with Pin 14 shorted - so thats
knackered for starters.
Click to expand...

Did you have a load on that PSU? Shorting PS-ON to ground on the 20-
or 24-pin power connector (from PSU to mobo) may not get the PSU to
power on. The PSU may be smart enough to know there is no point in
powering up completely if there is no load on it. Add a working hard
drive on one of the power taps from the PSU. Make sure none of the
taps from the PSU are connected to anything other than the test hard
drive. Then short PS-ON (pin 14, green wire) to ground (a black
wire). With a hard drive connected, do you see and hear the fan
inside the PSU is spinning? Does the hard drive spin up?

I have yet to see mention that this computer ever did power up before.
You never mentioned if this was a working system or something you just
put together and it has yet to work. If it was a working computer
before, what did you change that then caused the computer not to power
up? Did you add some other hardware?

You said the "power LED on the mobo" lights up when you connect the
old or new PSU to the motherboard. And which LED is that? The one on
the front of the case? Or an LED on the motherboard?
 
BertieBigBollox wrote ...





Did you have a load on that PSU? Shorting PS-ON to ground on the 20-
or 24-pin power connector (from PSU to mobo) may not get the PSU to
power on. The PSU may be smart enough to know there is no point in
powering up completely if there is no load on it. Add a working hard
drive on one of the power taps from the PSU. Make sure none of the
taps from the PSU are connected to anything other than the test hard
drive. Then short PS-ON (pin 14, green wire) to ground (a black
wire). With a hard drive connected, do you see and hear the fan
inside the PSU is spinning? Does the hard drive spin up?

I have yet to see mention that this computer ever did power up before.
You never mentioned if this was a working system or something you just
put together and it has yet to work. If it was a working computer
before, what did you change that then caused the computer not to power
up? Did you add some other hardware?

You said the "power LED on the mobo" lights up when you connect the
old or new PSU to the motherboard. And which LED is that? The one on
the front of the case? Or an LED on the motherboard?
Click to expand...

Yes. It was a working PC. Its a friends PC that has now stopped
working.

Apparently, the fan was making a noise and then it stopped working
altogether.

The LED on the actual mobo lights up.
 
No. Reseat all cards and memory. Try disconnecting or removing all unnecessary
items.
Google motherboard capacitors and look for pics of blown caps to see if that is
your problem.
Click to expand...

Tried this.
 
BertieBigBollox wrote ...
Yes. It was a working PC. Its a friends PC that has now stopped
working.

Apparently, the fan was making a noise and then it stopped working
altogether.
Click to expand...

WHICH fan stopped working? There are rarely less than 3 fans: CPU,
PSU, and 1 case fan. If it was the CPU fan, the BIOS will see the 3rd
wire (yellow) from the CPU fan effectively returning zero RPMs which,
to the BIOS, means that fan isn't spinning. If the CPU fan looks like
it isn't spinning, the BIOS immediately powers down the computer to
prevent the CPU from frying.

If you test the PSU using the PS-ON to ground short, you need to
disconnect the PSU from everything except the hard disk used as a
load. If, for example, the CPU fan wasn't spinning then the BIOS
shuts down the PSU but that would only happen if the 20- or 24-pin
connector from the PSU was attached to the motherboard.
 
BertieBigBollox wrote ...








WHICH fan stopped working? There are rarely less than 3 fans: CPU,
PSU, and 1 case fan. If it was the CPU fan, the BIOS will see the 3rd
wire (yellow) from the CPU fan effectively returning zero RPMs which,
to the BIOS, means that fan isn't spinning. If the CPU fan looks like
it isn't spinning, the BIOS immediately powers down the computer to
prevent the CPU from frying.

If you test the PSU using the PS-ON to ground short, you need to
disconnect the PSU from everything except the hard disk used as a
load. If, for example, the CPU fan wasn't spinning then the BIOS
shuts down the PSU but that would only happen if the 20- or 24-pin
connector from the PSU was attached to the motherboard.
Click to expand...

Dont know which fan. Like I said its a friends PC and I can get any
sense. They said the fan was very noisy so its probably the PSU fan I
guess - there is no case fan.

So, I suppose it could just be a dead CPU fan?
 
ALL power connectors are in place?
Remove all hardware except PSU -CPU/HSF -1 stick of memory -video. Make sure the 3 pin fan
header, reserved for the CPU is connected to the CPU fan.
Will it boot?
 
ALL power connectors are in place?
Remove all hardware except PSU -CPU/HSF -1 stick of memory -video. Make sure the 3 pin fan
header, reserved for the CPU is connected to the CPU fan.
Will it boot?
Click to expand...

Yep. Its an Intel socket 478 board so one 20-pin main connector and 1
square 12v power.

Tried as you suggest - still nothing. LED light on the mobo but
nothing when I short the power on pins (PSU doesnt start up or
anything elsee).

If the CPU fan is the problem, would this display the same symptoms?

Or is it looking more like u/s mobo?
 
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