PC shuts off after around 20 seconds. Help!

Freekill98

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May 11, 2013
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Hi, so basically my pc shuts down after being on for about 20 seconds, by the time I get into BIOs or even teh black screen whcih says "normal mode or safe mode" it just shuts down.

Things I have tried:
1. Wires
2. clearing CMOS/resetting BIOS
3. HDD (replaced)
4. PSU (used thermaltake PSU tester all voltages read fine)
5. Thermal Paste (thought maybe heat plus I needed to replace paste anyways)
6. CPU cooler
7. Graphics Cards

Things I dont think is the cause:
1. CPU/Motherboard - I don't think the pc would manage to stay on for at least 20 seconds if either the CPU or Motherboard was dead/broken

Can anyone think of anything else I can try? I am desperate as I don't want to just buy a new pc as I know most of the stuff in this rig still works feels like a waste if I did that.
 

Freekill98

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May 11, 2013
59
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10,630


well to give a rough guess of how long it lasts I have long enough to get ot the BIOS and stay their for about 5 seconds. I would of thought to get to the BIOS the PSU would have to be in LOAD already?

Also my PSU is kinda unqie in this house hold, mine plugs cable into the PSU rather then cables coming from the PSU
 

Freekill98

Honorable
May 11, 2013
59
0
10,630


Mangaged to get it to run for now running a memtest as we speak (first stick seems to have no problems so far been running for aorund 30mins 600 cycles. will do second stick after) . Problem I have is I know once I turn the pc off and try to turn it back on I will be back to it just shutting it self down after 20 seconds. The temps are reading 40C which is ideal. All the volts are reading ok in BIOs too. Also I checked the other two power supplies that are in the house however the connectors are wrong for my pc. 1 does not have a 24pin so that one is useless to me. The second on has a 24 pin but does not have a 8 pin for the board it has a 4 pin so is also useless to me. Won't be CPU as the pc does attempt to run and it seems to be running ok atm. The problem is when I restart :S.