Computer wont POST with new PSU

[gonemtbiking123]

Recently I purchased a Rosewill Fortress 450 to put into my HTPC/file servers build for better efficiency (old PSU is still functional). The problem is that after installing I can't even get it to POST (fans start up, so does HDDs but nothing coming up on my screen). I checked to see if my old PSU still runs it which is does, and tested the new PSU in my gaming rig and it works on there. Any ideas?

Specs:
Foxconn A74ML-K
AMD Phenom X4 9600
2gb DDR2
HD 5450
(Old PSU was taken off of an old HP desktop)

 

[Ubrales]

Check the 8-pins CPU power connector and make sure it is plugged in properly and the latch is engaged. Ditto for the 24-pins motherboard connector.

It does sound like a poor connection problem since you have tested the PSU in another computer and it is fine.

 

[gonemtbiking123]

I just rechecked the connections and they are fine. The MB only has a 4 pin connection so i reconnected that and the 24 with no luck, then tried the other 4 pin with no luck.

Another thing is once I power up the new PSU with the power button on the case I cant shut it off with the button. I have to flip the switch on the PSU in order to get it to shut off.

 

[Ubrales]

I just rechecked the connections and they are fine. The MB only has a 4 pin connection so i reconnected that and the 24 with no luck, then tried the other 4 pin with no luck.

Another thing is once I power up the new PSU with the power button on the case I cant shut it off with the button. I have to flip the switch on the PSU in order to get it to shut off.

One more thing to check is the CPU fan connection.

Regarding the 'hard shut off' - this has nothing to do with the PSU. This may be a clue why the PSU is not powering this computer. Looks like a case problem to me.

 

[gonemtbiking123]

Checked the CPU fan connection, it was fine.

Could it still be the case even though I have tried the old PSU after the new one and it worked fine?

 

[Ubrales]

Something could have been jarred loose during the changeover. Try repeating the experiment and don't be surprised if everything woks fine.

 

[gonemtbiking123]

I have swapped in and out 3 times and same result each time.

 

[Ubrales]

Rosewill underpowered?

 

[gonemtbiking123]

But then wouldn't it not have worked in my gaming rig?

I just gave my friend a call to get my multimeter back to test the voltages.

 

[Ubrales]

If it works in one computer then it should work in a different but similar computer.