Problems with computer power?

[Brooklin]

I'm trying to fix a friends pc. I've just changed the motherboard and
starting it with the power button is like starting an old car.

I have to hold the power button down, then the cpu fan runs, but when
I release it, the fan stops. The hard drive does not spin up at this
time. I have to press and hold the button for some time before I hear
the hard drive spin and the computer start to post.

Any ideas? Thanks in advance.

 

[Joel]

I'm trying to fix a friends pc. I've just changed the motherboard and
starting it with the power button is like starting an old car.

I have to hold the power button down, then the cpu fan runs, but when
I release it, the fan stops. The hard drive does not spin up at this
time. I have to press and hold the button for some time before I hear
the hard drive spin and the computer start to post.

Any ideas? Thanks in advance.

I dunno, just by reading the SUBJECT it seems like you already have the
right idea of what the problem may be. And if you think Power Supply is the
problem then all you need to do is to try with a working Power Supply.

And it sounds like Power Supply problem to me.

 

[w_tom]

This 'friend's PC" problem might involve any component in the power
supply 'system'. Not just a power supply. It is a 'system'. Two
essential tools for fixing computers - a screwdriver and a 3.5 digit
multimeter. Otherwise you must do wild speculation, swapping parts,
lots of wasted time, and add additional complexity to the problem.
Also that meter means your replies are useful

In your case, start with voltage on the purple wire (between computer
and motherboard) when computer is not powered and when power switch is
pressed. That would measure more than 4.87 volts. Then move on to
green wire voltage when computer is off and when power switch is
pressed. That would be more than 2 volts. Then drop to less than 0.8
volts when and after switch is pressed.

Of course, if these necessary conditions are not met, then post how
it failed AND the numbers.

Next is the gray wire. It should rise to more than 2.4 volts within
second of power switch pressed. Also confirm voltages on red, orange,
and yellow wires when and after power switch is pressed. These three
voltages should go immediately to above 3.23, 4.87, and 11.7 volts.

What those numbers are and how they change can then provide useful
replies. This data can be obtained in but two minutes AND eliminate
the 'try this and try that' nonsense. More important, numbers mean a
far more useful reply.

 

[Davy]

Have you doubled checked all the mobo settings both on mobo & in
bios.. also may be worth checking all the connections, also may be
checking the graphic card compatability.

Davy