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Question My desktop PC keeps shutting down with all motherboard lights off. What components might be at fault here?

Jul 12, 2020
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I have a desktop pc with asus z77v motherboard powered by a cooler master smps of 650 wattage. This machine is working flawlessly for almost 6 years.

Suddenly I have started facing a sudden shutdown problem. It shutdowns abruptly with no lights on in the mb. Not even the green light. After that it just doesn't switch on from the power button. No fan, no light. Then if I unplug it from the main power source and keep pressing the power button for 30 secs and then plug into the main power supply I see the green lights on the mb. Then I can boot normally from the power button and after 3-4 mins it just shutdowns again, even if I am on bios. And this cycle keeps going on.

CPU temp seems to be within normal limit - 39°C.

Could anyone please help me to identify what could be the problem. What component(s) might be faulty?

Due to the Covid-19 lockdown situation in my country (India) I couldn't take it to a repair shop. If I can atleast know about the faulty component, I can order a new one and replace it myself.

Thanks.
 

kanewolf

Titan
Moderator
I have a desktop pc with asus z77v motherboard powered by a cooler master smps of 650 wattage. This machine is working flawlessly for almost 6 years.

Suddenly I have started facing a sudden shutdown problem. It shutdowns abruptly with no lights on in the mb. Not even the green light. After that it just doesn't switch on from the power button. No fan, no light. Then if I unplug it from the main power source and keep pressing the power button for 30 secs and then plug into the main power supply I see the green lights on the mb. Then I can boot normally from the power button and after 3-4 mins it just shutdowns again, even if I am on bios. And this cycle keeps going on.

CPU temp seems to be within normal limit - 39°C.

Could anyone please help me to identify what could be the problem. What component(s) might be faulty?

Due to the Covid-19 lockdown situation in my country (India) I couldn't take it to a repair shop. If I can atleast know about the faulty component, I can order a new one and replace it myself.

Thanks.
Capacitors on the motherboard would be one possibility. Voltage regulators would be another. Even a CPU fan that stops reporting RPM could cause a PC to shutdown. There are many possible things in a 6 year old PC.
 
Jul 12, 2020
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Thanks.. There is another finding. After unplugging it from the main power source for 30 secs, and then when I plugged it in, I can see green light on in mb. Now if I don't switch on my computer and keep it plugged in to main power source for 3-4 mins, I see the green light get switched off automatically.

Does this help to identify the issue? Is it a smps issue or cmos battery issue or mb issue?
 
Jul 12, 2020
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Another notable observation, when I run memtest86 it hangs at 63% when one 8gb DDR3 ram module is inserted and at 34% when 2x 8gb DDR3 ram module is inserted.. I am not sure if it is a memory issue.. I tried to change the slots but the result is same.
 

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