atx 12v connector

jloots

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Jan 18, 2014
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I tried starting my computer one morning and it woudnt start. I opened the case and tried to see what the problem was, but could not find anything. I then disconnected everything, even the power supply. Connected then only the power supply. When I push power button the fans start runnning and then stops again. I disconnected the atx 4pin connector and push the power button and the cpu fan starts running. When I put the atx connector back nothing happens. Any suggestions please.
 

jloots

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Jan 18, 2014
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Everything is connected. The problem is with my atx 12v 4pin connector. When its connected nothing happens. When its disconnected some things start running.
 

Nuno Silva

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Jul 7, 2013
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Probably the problem is not on the ATX 12v connector, there are security fixtures on the motherboard that stop the computer to work if there is something wrong, usually a short circuit or memory not correctly placed.

Best way to find where the problem is is disconnecting everything but the cpu, power supply (connect atx 12v) and pcspeaker, and try to connect stuff one by one:

1 - nothing
pcspeaker should beep (you can read beep codes in your motherboard's manual) NOMEMORY ERROR

If no beeps then you have a short-circuit/power supply problem -> try with another power supply

- memory
If beep code is the same as previously then memory is not installed properly, actually this is a common mistake, you should place it in a way that both place holders "click", if you don't hear the "click" do it again

- graphics card
If your motherboard has on-board graphics you dont need to place graphics card to have a BIOS screen, if it doesn't place your graphics card, now you should have a BIOS screen when turning on the computer.

If all successful until now, connect the Hard Drive, you should be able to boot

If all successful until now connect everything else.

When one of the steps fail, just repeat the install/connection, it is easy to place memory or graphics card wrongly.
Also, I have seen some computers not turning on when inside the case, something was touching the back of the motherboard causing a short-circuit, that might also be the case, in last case, build the computer outside the case, you can turn it on by short circuiting the pins where the PWR connection is on your motherboard.

Hope this will help.


 
Aug 19, 2019
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Hey there, this is my firt post here at Tom's Hardware, I have been interested for a long time now about an issue related to this post.
Back in 2005 I bought a built from parts computer, ASUS motherboard, P4 3.0 Ghz, 1 Gb ram and 350W power supply. More or less in 2015 it started rebooting really every once in a distant while (once every 2-3-4 months)
Around 2016 I had to change the cmos battery, and almost by chance found out that there was no 4 pin atx 12v power connector in the PSU, therefore the atx 12v power in the motherboard had been disconnected from day one.
Fast forward in time early in 2019, I used the computer on a summer night (I am in the South Hemisphere) without any problems.
Next day it would not start, as a matter of fact for a couple times the fans started spinning but after that, no more.
Any ideas if it could have been related to the disconnected 4 pin atx 12v power?
Or better any ideas what could have happened? and any hint on a possible solution?


Thanks in advance.
 

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