PSU wont power PC up

blinky

A few things spring to mind:

a) Have you got both power leads to the motherboard connector (ATX and 12V 4pin lead)?

b) The most common cause of this type of issue is grounding out.

Best way to test is to remove the motherboard from the case and put in on something non conductive (e.g. motherboard box). Plug in only the essentials to the board:
i.e.
Processor + HS&FAN
1 stick of RAM
Videocard
Keyboard
Mouse
PSU (might be easier if you remove PSU from case).
Check there are no screws lying on or under the motherboard.

Find the two pins which are labelled for the ATX power button on the case. Briefly connect these two pins (paper clip, screwdriver, pliers should do it).
System should power on.

Unfortunately, you don't say what make the PSU is or which model P4 (if it's a Prescott I would think 400W+ is more likely required). There are a lot of poor quality PSU's about.

Rex_Mundi

If the PSU fan wont go when you switch on, then it would indicate a problem witht the PSU itself. If it is a new one, get it changed. If not, a new 300W PSU shouldn't set you back too much.

T4i

Look at this for proper PSU's.

http://www.devhardware.com/forums/t42355/s.html

Not too sure if its an old webby but I have to disagree with Tagan only having 2 polls.

IMO Tagan overtook Enermax some time ago.

Rex_Mundi

I would recommend Tagan to anyone. Excellent PSUs!

Toxteth_OGrady

Tagan, Enermax or Antec are all on a par imho.

Whatever you buy, don't touch Q-Tec with a bargepole unless u wanna set your PC on fire.

To determine psu rating needed use this online calculator.

:cool:

TOG

kaaloo

Thanks for all replies but I have 2 questions:

1 - I put this PSU in another case - it worked fine so I assumed it was the Motherboard

2 - The Motherboard lights up fine with the PSU (even tho the PSU wont spin) - would it do that if it had blown?

Rex_Mundi

Seeing as the fan in the PSU is not working, this looks like the PSU is on its way out. It may be that the PSU is generating some output, but not enough for the setup you are trying it out on.

It would be advisable to change the PSU anyway. It's not unheard of for them to produce a spike just before they finish completely and blowing components.

Joe_Bloggs

The motherboard has the capabilty to shut down the power supply if it detects a fault condition.
Stand by power does not require any cooling of the PSU to light the LED. Don't make any hardware changes whilst in a stand by power mode. Switch the mains of at a wall socket.
A fault condition exists or is thought to exist by the motherboard. Have you inspected the motherboard for potential shorts. Have you researched resetting the BIOS options in the CMOS. They may have been corrupted. Have you mounted the heat sink and fan adequately. The last point may seem trivial but I've been there and done that.
J_B.

kaaloo

Joe_Bloggs wrote:

The motherboard has the capabilty to shut down the power supply if it detects a fault condition.
Stand by power does not require any cooling of the PSU to light the LED. Don't make any hardware changes whilst in a stand by power mode. Switch the mains of at a wall socket.
A fault condition exists or is thought to exist by the motherboard. Have you inspected the motherboard for potential shorts. Have you researched resetting the BIOS options in the CMOS. They may have been corrupted. Have you mounted the heat sink and fan adequately. The last point may seem trivial but I've been there and done that.
J_B.

Yup! Cleared the bios/cmos via jumpers still no luck

drlight_2

Let the power drain out your motherboard before trying each solution, take the plug out the PSU for ten seconds, the the motherboard LED should fade out.

i seem to remember that the computer somewhere has some memory and won't boot up because of a previous problem. The pattern I got trying to get mine going seemed like it had protection.


Al