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PC won't turn on after a power cut

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#1 Cashy


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Posted 08 October 2014 - 03:52 AM

Hi guys and gals,

I'm new here so please be gentle 👍

There was a power cut the other day and my PC was on. After the power cut my PC won't start. It's appears that the surge protector has failed.

I first thought that PSU (thermal take tough power 750w) was dead. I removed it from my system and put a link between green and black and the PSU starts up. Checked voltages and all are present and correct.

I though that it might be the motherboard so I purchased a new one (Asus M5a78L-M USB3). I fitted into my system with just main power connector, 4 pin connector, processor (AMD Black Edition Phenom II X4 980 3.7GHz Socket AM3 6MB L3 Cache) and heat sink / fan (cooler master) and memory (corsair DDR3 8Gb). Tried to start it up and still nothing. Not even any POST bleeps.

I had noticed that SB_PWR (standby power) was on. This was also light up green on the old MB too. I have also noticed that there a slight whine from the PSU when power is connected to it. Not sure if that was the case before the problem or not but I don't think so.

I am asking you guys for help before I spend a fortune trying to figure out what's wrong.

Thank you taking the time to read this.

If you need can't more info please ask.


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#2 JohnC_21


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Posted 08 October 2014 - 01:19 PM

It's possible the PSU will check out fine by itself but when under load will fail.




Not sure if this would help but remove the power cord, hold the power button down for 30 seconds. Attach the power cord and see if the computer can boot.

Edited by JohnC_21, 08 October 2014 - 01:19 PM.

#3 Cashy

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Posted 09 October 2014 - 01:44 AM

I'll give it a shot and let you know in a while.


#4 zingo156


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Posted 09 October 2014 - 07:30 AM

As JohnC_21 mentioned, a lot of the time a psu will test fine without a load.


Here are some other things you can try:


Make sure you have the computer unplugged from power while removing or moving any hardware...


Try 1 stick of ram in 1 slot at a time (remove all other ram sticks). Move it to the next slot until you have tried that stick in all slots by itself. If you still have no post, try a different stick of ram in each slot by itself. If you have issues with the stick in 1 particular slot (a no post for example) the slot may be bad. It is also possible you have a bad stick of ram instead of the slot being bad, in this case the ram stick should cause the same problem all slots.


You may have a memory controller issue in which case if you have 4 slots, 2 may not work. With intel it should be 2 slots next to eachother channel 1 might be slot 0,1 and channel 2 might be 2,3. Trying with 1 stick at a time in all 4 slots is the best way to test everything.


If you never get a stable system with just 1 stick of ram in 1 slot (trying all sticks by themselves) remove all non essential hardware and try to get into bios:


Disconnect pci cards, pci-e cards - except a video card unless you have onboard in which case use the onboard video and pull the video card, hard drives, dvd drives, disconnect all usb headers as well. You should only have the power supply, main board, 1 stick of ram in 1 slot, the cpu and cpu cooler connected. You can also plug in a monitor and keyboard. Now try to power on the machine. If at this point you have no post screen or video etc, unplug the computer and pull the stick of ram, power back on and listen for a post fault beep code, you will need to hook up a motherboard speaker to hear any post fault code.


If you get no response next: remove all of the components from the computer case and connect only non essential hardware outside of the case, place the motherboard on a non conductive surface, a wooden table will do fine. Then try to power on again, you can short the power button pins on the motherboard, don't worry this is exactly what the power button does. Just touch a metal item to both power button pins to try to power the mainboard when outside of the computer case.


While you have the computer apart, look for blown or bulging capacitors on the mainboard and video cards etc examples: https://www.google.com/search?q=bulging+or+blown+capacitors+motherboard&noj=1&source=lnms&tbm=isch&sa=X&ei=Iz_YU6aDLsS2yASnjoKwAQ&ved=0CAgQ_AUoAQ&biw=1031&bih=603 please report any caps you suspect may be bad, you can take a picture and post here if you are unsure.

If I am helping you with a problem and I have not responded within 48 hours please send me a PM.

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