Computer won't run when CPU power is connected, if its connected it cycles on and off every couple seconds?

[Kiefermac92]

I upgraded parts to my existing computer (ASUS Maximus VII Hero and Intel i7-4790K). when I had it all rebuilt, I try to turn it on and it starts for half a second and then shuts down and a couple seconds later it tries to start again, cycling on and off. I made sure all cables are correctly connected and tried it again, but the same issue. I removed everything and left only the Motherboard, CPU, PSU and a fan connected. I removed the 8 pin CPU power and tried and it runs up however there is no beeps or noise, it just runs. Also the fans only run if connected to the CPU Fan port and not the Chassis Fan ports, with or without the CPU power connected (the fan spins for a second with CPU power connected and fan in CPU port, but only for half a second.) I have read it could be a fault with the CPU, MOBO or PSU. I tried the PSU in my old MOBO and it runs up without hassle. I also tried running the new MOBO without the CPU connected and it starts and stops like above, so I'm hoping its the MOBO thats defective not the CPU. Is there anything I can do to distinguish that its the MOBO, I cant try the CPU in the old one as its AMD.

Thanks

 

[Joe Porter]

Have you tried resetting the CMOS? Also I think you will need a slot of ram in there to get it to post. try putting one slot of ram in as well. try it in every slot, if it doesn't boot still try a different stick in each slot.

 

[Kiefermac92]

There is a CMOS reset button on the Motherboard, which I tried, but still the same issue.

I didn't try it with ram in after I removed everything, however it runs without ram (with no posts) when the CPU power is not connected?

 

[Joe Porter]

does it stay running or just turn off with no RAM? I would expect it to just turn off by itself after a brief second.

 

[Joe Porter]

Do you get any beeps at all? if so what and under what circumstances?

 

[Kiefermac92]

It stayed running with and without ram when the CPU power was not connected. I switched it off around 30 seconds in.

The old MOBO ran when I had that plugged in to only the PSU and old CPU to make sure the PSU was working.

 

[Kiefermac92]

No beeps at all. When everything is plugged in, the computer starts long enough to spin the CPU fan (Chassis Fans dont run?) and turn on the CPU Cooler light and switches off, cycling on and off. There is a 2 digit screen on the MOBO (think its for fault codes) however it just states "00" but isn't on long enough to do anything. When the CPU power is unplugged, the computer will start but there is no beeps and the chases fans don't run. I let it run for around a minute before switching it off.

 

[Joe Porter]

Has the thermal paste been applied properly to the processor? It is possibly shutting off as it might be instantly overheating.

 

[Joe Porter]

Also make sure the CPU fan is plugged into the 4pin connector on the MOBO I think it is even labbeled up CPU_fan on that MOBO!

 

[Kiefermac92]

Yes, I used Arctic Silver, on the CPU and my cooler is a H100i. It ran without the CPU cooler and CPU power cable not connected. I didnt leave it running long without the cpu cooler attached, but it did run.

 

[IronVirgin]

No beeps at all. When everything is plugged in, the computer starts long enough to spin the CPU fan (Chassis Fans dont run?) and turn on the CPU Cooler light and switches off, cycling on and off. There is a 2 digit screen on the MOBO (think its for fault codes) however it just states "00" but isn't on long enough to do anything. When the CPU power is unplugged, the computer will start but there is no beeps and the chases fans don't run. I let it run for around a minute before switching it off.

First of all this mobo will not beep it have no speakers. You have that digital display to show you problems.
I think you made same mistake like me and destroyed motherboard when put cpu inside. motherboard have tiny pin connectors in cpu socket.
Now grab flash light and and magnifying glass and check for bend pins. If there is even one pin bend whole mobo can go to rubbish.

 

[Kiefermac92]

Also make sure the CPU fan is plugged into the 4pin connector on the MOBO I think it is even labbeled up CPU_fan on that MOBO!

I had a fan connected to the CPU fan port, and discovered it would run the fan in only that port and not the Chassis fan ports

 

[Kiefermac92]

No beeps at all. When everything is plugged in, the computer starts long enough to spin the CPU fan (Chassis Fans dont run?) and turn on the CPU Cooler light and switches off, cycling on and off. There is a 2 digit screen on the MOBO (think its for fault codes) however it just states "00" but isn't on long enough to do anything. When the CPU power is unplugged, the computer will start but there is no beeps and the chases fans don't run. I let it run for around a minute before switching it off.

First of all this mobo will not beep it have no speakers. You have that digital display to show you problems.
I think you made same mistake like me and destroyed motherboard when put cpu inside. motherboard have tiny pin connectors in cpu socket.
Now grab flash light and and magnifying glass and check for bend pins. If there is even one pin bend whole mobo can go to rubbish.

The display shows nothing bar "00" when it runs without the CPU power connected, it doesnt run long enough with it connected to show anything. I also double checked all the pins on the socket for the CPU and there is no damage or bend in any of the pins?

 

[rollingbarrels]

The problem is either your motherboard or your power supply or more unlikely your CPU. I had a very similar issue a while back and it turned out to be those. Try putting your old hardware back in and see if the problem occurs. If it doesn't then that rules out the PSU. Then you can try booting the computer without any CPU in to see if the problem still occurs. A PC should be able to power on without a CPU, it just won't POST or anything. If you get the problem when your CPU socket is empty then it must be a problem with your motherboard. Since you just got a new motherboard, it is possible that it was defective in the first place. Sometimes components can be broken even when they are new out of the box in which case, you should RMA your motherboard.

Also, what is your PSU?

 

[Kiefermac92]

The problem is either your motherboard or your power supply or more unlikely your CPU. I had a very similar issue a while back and it turned out to be those. Try putting your old hardware back in and see if the problem occurs. If it doesn't then that rules out the PSU. Then you can try booting the computer without any CPU in to see if the problem still occurs. A PC should be able to power on without a CPU, it just won't POST or anything. If you get the problem when your CPU socket is empty then it must be a problem with your motherboard. Since you just got a new motherboard, it is possible that it was defective in the first place. Sometimes components can be broken even when they are new out of the box in which case, you should RMA your motherboard.

Also, what is your PSU?

Yes I tried the PSU with my old Motherboard and CPU and it ran up, so I hope I can rule out the PSU.

I tried running the Motherboard without the CPU and it was giving the same problems, so hopefully it was the Motherboard.

However I bought both the Motherboard and CPU together so I was hoping to confirm what was defective so I don't need to return both.

Also my PSU is a Corsair RM750 Gold.

 

[Joe Porter]

What is your old MOBO? Can you try your new CPU in that or does it not fit?

 

[rollingbarrels]

I will say that the problem is definitely your motherboard, you should be okay after you get it replaced.

 

[Kiefermac92]

What is your old MOBO? Can you try your new CPU in that or does it not fit?

No its an ASUS M5A99FX PRO which doesnt support the Intel i7 (AMD Board).

I may have a way to check the CPU on another computer, I will let you know the outcome.