PC shutdown after 3 secounds

Ibrahim Ticevic · Aug 8, 2014

Hey
I have G31-M7 TE motherboard , and when i try to turn pc on after 3 seconds it power off and i can't turn it on again , it was working fine since monday , if anyone can help me , thanks in advance

Karsten75 · Aug 8, 2014

sounds like a cooling issue. Check that the CPU fan turns in those 3 seconds. If you built this PC, did you apply thermal paste and seat the heatsink correctly? Did you connect the CPU fan and CPU aux power connectors?

Ibrahim Ticevic · Aug 8, 2014

Karsten75 :

yes , cooler turns on , LED's turn on , monitor too and then it shutdown

InvalidError · Aug 8, 2014

Three seconds from cold-start is much too fast to be a CPU overheat issue since the CPU is merely running BIOS code at that stage.

The two most likely issues I can think of would be a short somewhere or a power supply issue.

What is the PSU model and how old is it?

Ibrahim Ticevic · Aug 8, 2014

InvalidError :

PSU MODEL is KY-400ATX P4 and it's old 3 years i think

InvalidError · Aug 8, 2014

Ibrahim Ticevic :

There is a fairly high probability this is your problem. Those PSUs last 2-3 years - there was a thread just a few days ago about someone else having a similar issue with a KY-300ATX.

Ibrahim Ticevic · Aug 8, 2014

InvalidError :

PSU is working ,tested on other PC

InvalidError · Aug 8, 2014

Ibrahim Ticevic :

That only proves that the PSU has not croaked for good yet. It could still be defective but not badly enough to fail outright on the other PC. Unless the two have identical hardware configuration, the loads on the PSU will be different and that might be just enough to avoid shutdowns/restarts... for now.

Did you try the other PC's PSU in your problematic PC? If the random shutdowns stop (assuming your other PSU has adequate ratings) then this substantially increase the probability of the PSU being the problem. If you still have issues, it could be that your other PSU is also bad/borderline.

Ibrahim Ticevic · Aug 9, 2014

When i plug power cable in PSU , PC automaticly power up and turn off :I

carlo_bigtunes · Aug 9, 2014

hi ibrahim,
biostar G31 m7-TE is a bad motherboard G31 there's a lot of problem with this MB.
with your case "ONLY TURN ON FOR 3s" , your MB got a "SHORT MOSFET"

tested :
- if only 24 pin without 4 pin power plug in, MB still power on but no display coz there's no power to CPU
- if 24 & 4 pin plug in, only spin for 3s then shutoff, this mode to protect CPU from overvoltage
- for power on it self, there's an IC IO call "ITE " was bad

suggest :
- is there a friend or technician had a hot air, you can ask them for replace mosfet

InvalidError · Aug 9, 2014

Try unplugging the soft-power switch from the motherboard - if the switch is stuck closed, that would explain why the PC turns on as soon as you connect the PSU to mains then turns off after a few seconds.

Ibrahim Ticevic · Aug 9, 2014

I'll try these from above , i'll let you know

Ibrahim Ticevic · Aug 9, 2014

I've tried plugging in motherboard 24-pin cable without 4 pin , and it won't shutdown , beside when i connect both 4 pin and 24 pin , it shutdown a-a

carlo_bigtunes · Aug 9, 2014

correct, only 24 pin plug in, motherboard cannot shutoff from power button.only from psu switch...
100% there's short mosfet..

Ibrahim Ticevic · Aug 9, 2014

carlo_bigtunes :

Any clue how can i fix it ?

carlo_bigtunes · Aug 9, 2014

here i give you a picture..
Red = MOSFET , find 1 broken and replace it,
Green = PWM, supply voltage to FET.

how to find broken mosfet:
-use multimeter digital, beep mode, don't plug any power to motherboard
-black probe to negatif 4 pin,
- red probe to each leg FET ( there a 3 led, DRAIN, GND, SOURCE)
- if 3 of leg had beep sound , there a BROKEN FET
- if only 2 BEEP it's a NORMAL FET

Ibrahim Ticevic · Aug 10, 2014

I would try to get help from my friend , i would like to replace them all , are they expensive ? , i'd like to order them online

InvalidError · Aug 10, 2014

Ibrahim Ticevic :

Depending on the actual ratings, quantity and brand, the price can be anywhere from $0.60 to $3 when buying in small quantities from major brands like Fairchild, ON Semi. In large quantities (whole reels) like mass production and large repair shops use, the prices go down to about $0.25.

PC shutdown after 3 secounds

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