Power won't stay on

I just bought a new nMediaPC 200SA case and transferred all the
components including my Asus P4P800-VM MB from an old machine to the
new case. After installation, the power won't stay on in the new
machine. I hit the power button and the PSU fan spins up and I get a
power light on for a couple of seconds, then everything shuts off.
Needless to say these same exact components were all working fine in
the old case.

I noticed that if I disconnect the ATX12V connection from the PSU to
the MB the power will stay on (but of course it won't boot like that).
Also, if I hit and release the power button then immediately hit and
HOLD the power button, it will stay on and boot normally. Then once I
release the power button if shuts off immediately.

Here's things I have tried:
- removed and reseated all cables to everything
- used a power switch from another case (known good)
- replaced the PSU w/known good
- disconnected everything from the PSU except the MB

At this point I'm at a loss. The case is the only thing that has
changed, but it seems from my troubleshooting that I have eliminated
the case as the problem (since the problem still exists even with a
power switch from a different case). I suppose I could try replacing
the MB but before I go that drastic I'd like opinions on what the
problem might be. I'm curious about the fact that the power stays on
if the ATX12V is disconnected. Also, why does the power stay on when I
hit and hold the power button?

Thanks!

wrote:

I just bought a new nMediaPC 200SA case and transferred all the
components including my Asus P4P800-VM MB from an old machine to the
new case. After installation, the power won't stay on in the new
machine. I hit the power button and the PSU fan spins up and I get a
power light on for a couple of seconds, then everything shuts off.
Needless to say these same exact components were all working fine in
the old case.

I noticed that if I disconnect the ATX12V connection from the PSU to
the MB the power will stay on (but of course it won't boot like that).
Also, if I hit and release the power button then immediately hit and
HOLD the power button, it will stay on and boot normally. Then once I
release the power button if shuts off immediately.

Here's things I have tried:
- removed and reseated all cables to everything
- used a power switch from another case (known good)
- replaced the PSU w/known good
- disconnected everything from the PSU except the MB

At this point I'm at a loss. The case is the only thing that has
changed, but it seems from my troubleshooting that I have eliminated
the case as the problem (since the problem still exists even with a
power switch from a different case). I suppose I could try replacing
the MB but before I go that drastic I'd like opinions on what the
problem might be. I'm curious about the fact that the power stays on
if the ATX12V is disconnected. Also, why does the power stay on when I
hit and hold the power button?

Thanks!


The only thing you have not checked is the mounting of the
motherboard to the floorpan of the new case. Is there a short?
Is a standoff touching a trace or component outside of the
zone for it? Or a mounting screw on the component side of the
motherboard touching a component?

In article .com,
wrote:

I just bought a new nMediaPC 200SA case and transferred all the
components including my Asus P4P800-VM MB from an old machine to the
new case. After installation, the power won't stay on in the new
machine. I hit the power button and the PSU fan spins up and I get a
power light on for a couple of seconds, then everything shuts off.
Needless to say these same exact components were all working fine in
the old case.

I noticed that if I disconnect the ATX12V connection from the PSU to
the MB the power will stay on (but of course it won't boot like that).
Also, if I hit and release the power button then immediately hit and
HOLD the power button, it will stay on and boot normally. Then once I
release the power button if shuts off immediately.

Here's things I have tried:
- removed and reseated all cables to everything
- used a power switch from another case (known good)
- replaced the PSU w/known good
- disconnected everything from the PSU except the MB

At this point I'm at a loss. The case is the only thing that has
changed, but it seems from my troubleshooting that I have eliminated
the case as the problem (since the problem still exists even with a
power switch from a different case). I suppose I could try replacing
the MB but before I go that drastic I'd like opinions on what the
problem might be. I'm curious about the fact that the power stays on
if the ATX12V is disconnected. Also, why does the power stay on when I
hit and hold the power button?

Thanks!

Is the CPU fan cable connected to the CPU fan header ?

Paul