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Solved pc won't start, CPU fan starts then stops in loop, please help

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vblanche

PCHF Member
Feb 8, 2020
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#1
Hello, I would need help from you guys, thanks in advance.

ok, first, the system specs: it's an old machine.
Motherboard: gigabyte GA-P67A-UD4-B3 rev1.1 socket 1155
CPU: Intel Quad Core I5-6600k 3.5 GHz
GPU: asus ENGTX560 DCII OC/2DI/1GD5
RAM: 2x4GB GSkill DDR3-1600 PC3-12800
PSU: corsair AX750
HDD: SSD samsung 840PRO 128GB + HDD WD 640GB

pc used to work fine from day one, the day I've built it (maybe 6-8 yrs ago), until 2 days ago. it was difficult to start it and reach windows10, I had to repeat the start procedure few times. And today, nothing: it won't start at all, when I press the start button, it seems to start, the CPU fan starts, but then it stops after 2-3 sec, and it keeps restarting in loop...I can't reach any BIOS. I've unplugged a maximum of devices/peripherals: there is only the SSD, RAM and CPU. still nothing...
i can't see anything shorting the motherboard.

What should I look at? any advice?

many thanks
Vincent
 
#2
Welcome to PCHF vblanche,

Some checks that you can do for us if not already done;

If Windows is on the SSD, disconnect the SSD from the MB to see if it changes anything.

Disconnect and reconnect the 24-pin ATX main power connector and the 8-pin ATX 12V power connector at both the MB and PSU sockets, be firm but do not apply too much pressure when pressing them into the MB sockets.

Reseat both sticks of RAM to make sure that they have a good/clean connection in the slots.

Try one stick of RAM at a time and by inserting them into each one of the four slots.

If no change after doing the above, test your PSU to make sure that it is not that which is powering up/down, use the method in the Corsair video here no need to even connect a chassis fan to the PSU.

No rush doing the above as I will not be around for a couple of hrs as I have other commitments, will check back on my return and good luck.
 
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#5
So, here is where I am:

phillpower2 said:
If Windows is on the SSD, disconnect the SSD from the MB to see if it changes anything.
Click to expand...
indeed, win10 is on the SSD, so I disconnected, no change.

phillpower2 said:
Disconnect and reconnect the 24-pin ATX main power connector and the 8-pin ATX 12V power connector at both the MB and PSU sockets, be firm but do not apply too much pressure when pressing them into the MB sockets.

Reseat both sticks of RAM to make sure that they have a good/clean connection in the slots.

Try one stick of RAM at a time and by inserting them into each one of the four slots.
Click to expand...
did that too. and yes, there is improvement: I reseat only one stick of RAM, testing each slot one by one. At first, I thought one stick was defective, but in fact there are both ok, on any slot. The pc - CPU, CPU fan, 2 RAM sticks in place but without the SSD (so no hard disk whatsoever) and no GPU - is starting, the CPU fan is on, the phase LED are on, then are off, and the CPU fan is still on.

phillpower2 said:
If no change after doing the above, test your PSU to make sure that it is not that which is powering up/down, use the method in the Corsair video here no need to even connect a chassis fan to the PSU.
Click to expand...
I also did this test. The chassis fan starts, the PSU fan is on only 1-2 sec (but I guess that's normal, the PSU fan is on only if it's hot, isn't it?)

I haven't tried to rebuild and start. will do asap.

thanks
 
#6
Everything looks to be working as it should in your above post.

Just the boot SSD, GPU and keyboard should be added for now to see if the computer will now POST.
 
#8
As said above, everything is working as it should be based on the content of your reply #5, your PSU has a thermally controlled fan than only spins up when it needs to, you were right to double check though (y)
 
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#12
Great news & thanks for letting us know that all is now well with the computer (y)

I suspect that the cause was either a loose connection or a poor contact on one of the gold fingers on the RAM and the contacts in the memory slot.

You are welcome btw :)
 
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