# Interesting problem with ATX 12v 4Pin



## delusns

Hello,

I finished building my system, installed windows, etc and everything was running fine. Suddenly the power shuts off. When I tried to turn it back on, the power, fans etc would all turn on for a 1 sec and turn back off. Then it finally stayed off. Long story short, I ended up buying a new PSU and Mobo. Same thing happens. I isolated the problem to the ATX 12V 4 pin connector. When it's plugged in, the mobo won't turn on but when I unplug it, the mobo will turn on. Does this mean my CPU is fried? Any help would be appreciated. Thanks.

P.S. This problem occurs on both identical mobos. Troubleshooting with just the 24 pin and 4 pin connected outside case.

Specs:
Mobo: ECS GF7100PVT-M3
PSU: Thermaltake Purepower 500 ATX 12v 2.0
CPU: Pentium D 3 Ghz
Ram: 2GB


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## oscaryu1

If it runs fine with the 12V unplugged, then leave it be.


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## StrangleHold

delusns said:


> Hello,
> 
> I finished building my system, installed windows, etc and everything was running fine. Suddenly the power shuts off. When I tried to turn it back on, the power, fans etc would all turn on for a 1 sec and turn back off. Then it finally stayed off. Long story short, I ended up buying a new PSU and Mobo. Same thing happens. I isolated the problem to the ATX 12V 4 pin connector. When it's plugged in, the mobo won't turn on but when I unplug it, the mobo will turn on. Does this mean my CPU is fried? Any help would be appreciated. Thanks.
> 
> P.S. This problem occurs on both identical mobos. Troubleshooting with just the 24 pin and 4 pin connected outside case.


 
If its doing the same thing with a new P/S and board, have you got a case speaker hooked up to get the Bios beep tones?


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## delusns

oscaryu1 said:


> If it runs fine with the 12V unplugged, then leave it be.


The 12v is supposed to be in for the CPU power. Without it, the mobo turns on but won't do anything else.


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## delusns

StrangleHold said:


> If its doing the same thing with a new P/S and board, have you got a case speaker hooked up to get the Bios beep tones?


Yup. But with the 12v plugged in, the mobo won't turn on, no beep, no fan or anything.


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## StrangleHold

What tone are you getting without the 4pin 12V CPU power pluged in. Usually a CPU or Memory tone is a repeative drive you crazy tone. Starting to sound like your CPU or Memory went out, plus since you have already replaced the board and P/S and the problem stayed the same.


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## delusns

Thanks Strangehold. 

To be honest, I tried so many different scenarios with wire connections and wasn't listening to tones with the speaker wire in. I'll be sure to listen for it later. If it does do the crazy beeps/tones, that means its the CPU you think? The ram should still be good but I'll test that out too. Much thanks.


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## oscaryu1

It could mean many things. Look up your BIOS Beep code.


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## delusns

*Nope*

Ok so I cleared CMOS. Connected ONLY the 24 pin to mobo with speaker and power fpanel wires attached. 12V NOT attached. Still same thing. CPU and PSU fans turn on but no sound or anything. @!#$%

Gonna try a new CPU tomorrow.


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## ChrisW92410

had it happen to me JUST before i did a new or my most current build...but mine was a bad mobo, shit was a 2yr old asus and had my cousin (computer programmer) look at it he said samething i was thinking...bad mobo...might not be your case but probably not out of the question


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## delusns

*Ugh*

It seems a little odd that 2 motherboards would have the identical problem. I went back to exchange the board for a new one (only allowed to exchange for same brand/type). I also have a new CPU to test out. Going to try both the CPU and mobo with each component connected one-by-one to isolate the problem. I knew a good mobo with DVI and 8-Channel audio for 50 bucks was too good to be true...


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## zxcvbnnm

delusns said:


> It seems a little odd that 2 motherboards would have the identical problem. I went back to exchange the board for a new one (only allowed to exchange for same brand/type). I also have a new CPU to test out. Going to try both the CPU and mobo with each component connected one-by-one to isolate the problem. I knew a good mobo with DVI and 8-Channel audio for 50 bucks was too good to be true...



How did you get this sorted because i'm having the exact same problem?


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## Russian777

ChrisW92410 said:


> had it happen to me JUST before i did a new or my most current build...but mine was a bad mobo, shit was a 2yr old asus and had my cousin (computer programmer) look at it he said samething i was thinking...bad mobo...might not be your case but probably not out of the question




programmers dont know a thing about computers, only about programs.


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## rsuryase

I have the same problem. My motherboard is ASUS P5W DH Deluxe, PSU is XION Supernova 600W ATX 2.2. The motherboard won't power on if the 4pin 12V CPU power is connected. It will turn on if disconnected. I swap to an older PSU, Enermax 450W ATX 1.2 and the mobo powers up. I tried the Xion on a P4P800 Deluxe and the same problem occurs. Is the problem with the PSU?


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## rsuryase

I found out how to solve the problem. If the pc won't power on, I unplug all the attachment peripheral power cables from the PSU, the pc will turn on now, Then I turn off the pc and re-attach all the peripheral power cables and turn on the pc again. This works for me. I think it's a grounding issue, one of the cables may be grounded.


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