PSU 4-Pin +12V Connector - Purpose

Dazzlercee · 15 Dec 2006 at 12:09

I have a system that will not post/boot when the 4-Pin +12V supply is connected to the motherboard.

What is the purpose of this connector? Is it an additional supply for the CPU?

I cannot understand why the system will not boot, it was fine! If the 4-Pin supply is removed then the board powers up and the fans spin but obvioulsy the system will not post.

If the additional supply is for the CPU then this leads me to the conclusion that the CPU has failed.

Any help appreciated before it all has to go back to OC for testing. :eek:

steve258 · 15 Dec 2006 at 15:44

Yes the extra 4pin is dedicated to CPU, newer high end mobo has 8pins.

What is your spec? and what PSU are u using??

Dazzlercee · 15 Dec 2006 at 15:51

Its an ASUS M2N-E mboard, 4200+ CPU, Leadtek 7900GS graphics, 2GB Corsair and a Tagen 430W PSU. One HD and one optical drive.

The system was working with an ATI 1600 but when he swapped it for the 7900GS the problems started.

If I remove the CPU the fans will spin constantly, as soon as CPU is reseated the system reverts to a quick spin of the fans and then stops.

I am going to test the CPU in another mboard tomorrow. If that works then it is most prbably his Asus mboard.

Captain Fizz · 15 Dec 2006 at 16:03

Dazzlercee said:
The system was working with an ATI 1600 but when he swapped it for the 7900GS the problems started.

So you don't think it would be the fact that the new GFX card is drawing too much power?

Was working before changing the GFX card, you change the GFX card, it stops working.
You have not changed the CPU...

Can you try the ATi1600 back in there?
If it works - It isn't the mobo or CPU.

It's either the GFX card, lack of power or something else.
(Power SHOULDN'T be an issue though)
You have the GFX card plugged in nicely?
Tried re-seating?
Tried that GFX card in another system?

Dazzlercee · 15 Dec 2006 at 16:09

Tried all that. Initially I thought it was power so he purchased the Tagan (7900GS needs 20A combined, I run a 8800 from same power supply with 3 HDs and optical drive - no probs).

I have reseated ram, ati 1600 and CPU - still same problem with the new Tagan PSU.

There are only two instances where everything powers up (but no post obviously):

1. No 4_Pin ATX power connected.
2. No CPU inserted.

I should find out either way tomorrow when I am able to test with other mboard / CPU.

(The changing of graphics cards may just be a coincidence unless he changed the card without removing power first :eek:

)

Captain Fizz · 15 Dec 2006 at 16:14

Dazzlercee said:
(The changing of graphics cards may just be a coincidence unless he changed the card without removing power first )

0_O

Tried with old PSU and old card?
(As it was originally - Working)
It may be the Tagan...

steve258 · 15 Dec 2006 at 16:27

is it a 430 U15 easycon??

maybe silly but have you plug in the correct 4 pins?? there should be one 4 pins that can be "combined" with the 20pin atx connector to form a 24pin atx, and there is the other 4pin (blue i think) that is dedicated for the stand alone 4pin +12V socket.