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Custom PC turns on then shuts off instantly...

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January 16, 2013 5:41:18 PM

Me and my brother built a custom PC. It was running and running quite great for about a year. Suddenly it began to be very slow, and then one day the screen went pink and I had to turn off the PSU to turn off the computer. Ever since, if I turn on the PSU and hit the power switch, it turns on and then turns instantly off. All fans spin and then it shuts off.

I did a breadboard build, where I believe I narrowed down the issue. With only CPU, Speaker, PSU, and Mobo plugged in...I had the same problem. Everything powered on for a split second and then powered off. However, if I disconnected the 8-pin power supply to the motherboard, the computer will turn on and stay on (of course it doesn't boot, but it stays powered on...). If the 8-pin power is connected, then I get the turn-on-turn-off effect. Also found if I hold the memOK button it will stay on even with 8-pin connected, but when I let go of memOK button it turns off, but I couldn't find any explanation for why that is.

I have tested the power supply, and it is good (850w, more than sufficient for our build -- we did our research).

Anyhow, like I said, the build was working very well, then suddenly quit after beginning to act slow. I believe it to be either the CPU or the motherboard. I don't have the funds to buy both, so I'd like to get it right the first time, if at all possible. The CPU appears to have "corrosion" around the edges (on the metal surface ONLY - the chip itself has no damage at all). The metal appears to be slightly flaky around the edges. I know my brother was overclocking, but he was always cautious of temperatures.

The only thing that makes me doubt if this was is the CPU is when the computer "died" - the screen turned purple, which i've read indicates a faulty graphics card. So if the motherboard failed it would seem likely that the graphics card, cpu, and all other devices plugged into the motherboard would have also failed.

AMD Phenom II X4 965 Black
Not sure of exact motherboard model, but it is compatible with CPU - like I said, the build was working well for a year or so.
TX850W Corsair PSU


I've been banging my head on the table for the last few months trying to find answers to this, but can't seem to find somebody with the same issue.
January 16, 2013 6:40:37 PM

try your ram could be a compatiblity issue
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January 16, 2013 6:50:17 PM

stuartrenouf said:
try your ram could be a compatiblity issue



Like I said, build was up and running for a year. It ran very fast and very strong. We did our research before building. All parts are compatible.
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a b à CPUs
January 16, 2013 7:08:34 PM

He saying your RAM modules might have gone bad. Do you have a case speaker attached to your board? They usually beep when there's booting issues.
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January 16, 2013 10:41:11 PM

payturr said:
He saying your RAM modules might have gone bad. Do you have a case speaker attached to your board? They usually beep when there's booting issues.


This is my problem: "I did a breadboard build, where I believe I narrowed down the issue. With only CPU, Speaker, PSU, and Mobo plugged in...I had the same problem. Everything powered on for a split second and then powered off. However, if I disconnected the 8-pin power supply to the motherboard, the computer will turn on and stay on (of course it doesn't boot, but it stays powered on...). If the 8-pin power is connected, then I get the turn-on-turn-off effect."

The system cannot boot or beep because the system will not stay powered on when BOTH PSU cables are plugged into the motherboard, and if only the 24-pin is plugged in it boots up, but then there is no power to CPU so there is still no boot. I have this issue when I breadboard before even putting the RAM in.
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January 16, 2013 10:49:46 PM

payturr said:
He saying your RAM modules might have gone bad. Do you have a case speaker attached to your board? They usually beep when there's booting issues.


Again on RAM - Never had any issues with beeping, blue screens, or anything like that. It was just a sudden crash. The computer had been going slow in its final weeks, but never had any of the bad RAM issues. There is a case speaker and it doesn't beep at all because I cannot get the computer to stay powered on unless I remove the 8-pin PSU supply.
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a c 89 à CPUs
January 16, 2013 11:00:57 PM

have you tried a different PSU? Do you have access to another system where you can change the ram and test it or even swap out the CPU?
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January 17, 2013 12:14:25 AM

bgunner said:
have you tried a different PSU? Do you have access to another system where you can change the ram and test it or even swap out the CPU?



I tested the voltage of every cable on the PSU and checked it with the voltages the manufacturer said each should put out. Is that not really a good test of a PSU?

We've only built one computer and I don't have spare parts of anything lying around. =(
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January 17, 2013 12:19:40 AM

I am just curious to see if I can find the most likely culprit to avoid having to spend $500 to find the faulty item.

There are really only 3 things it could be (based on my breadboard build):
CPU
Motherboard
PSU

I've tested the PSU with a multimeter and found all to be well.

Purple screen on crash, from what i've read, signifies faulty GPU. However, the computer would still boot regardless of GPU, but it seems logical that a failing motherboard would mean all other components would not work (thus the seemingly faulty GPU and CPU). However, this is the first time i've experienced a computer failure so I don't know for sure if this purple screen is a result of CPU failure.

CPU appears to have corroded around the edges of the metal face of the processor. I don't know if this is typical or if this is damage. The CPU was overclocked, but temperatures were monitored. Again, this is our first build and i've never seen the used CPU of another gaming computer to see if such "corrosion" is typical of higher end PCs. I think this is the most likely culprit, but again I don't have anything to compare it to.
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January 17, 2013 2:02:56 PM

Tried another psu...same problem persists
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January 18, 2013 3:12:03 AM

Apparently this is a rare problem....?
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a c 89 à CPUs
January 18, 2013 3:25:55 AM

I'm not sure how to test a CPU with out changing it into another board. how many sticks of ram do you have? If more then one try one stick at a time and see if it boots. If not then your right back where we started. can't hurt to try. I assume you are using DDR3 ram? do you have a friend you could swap out the ram in there machine just to run a test on it? this would narrow it down to CPU or mother board. But from there the next test would be swap CPU's and test board or CPU.

Sry i don't have better answers but it is a process of elimination at this point.
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January 18, 2013 3:43:28 AM

He saying your RAM modules might have gone bad.
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January 18, 2013 6:54:19 AM

bgunner said:
I'm not sure how to test a CPU with out changing it into another board. how many sticks of ram do you have? If more then one try one stick at a time and see if it boots. If not then your right back where we started. can't hurt to try. I assume you are using DDR3 ram? do you have a friend you could swap out the ram in there machine just to run a test on it? this would narrow it down to CPU or mother board. But from there the next test would be swap CPU's and test board or CPU.

Sry i don't have better answers but it is a process of elimination at this point.


The RAM just can't be the problem. Breaboard built with only CPU, PSU, and Motherboard and the computer turns on then turns off. RAM is not involved in this process. I can't get the computer to a point where the RAM is even accessed to begin POST.

Details again: CPU appears to have corrosion on the metal surface (only way I can think to describe this is it appears kind of flaky). Pins are OK, and there is no sign of heat damage on the chip itself...only the corroded edges of the metal surface.

When ONLY the 24-pin power supply is connected, the computer will turn on and keep running. If the 8-pin AND the 24-pin power supplies are connected, then the system turns on then off after a split second. I cannot get the system to stay on with the 8-pin connected. There are no beeps from the speaker because there must be a CPU present to even begin POST, right? If it was the RAM then it stands to reason that there would be beeps, but the system will not power on if both PSU cables are connected.
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a c 89 à CPUs
January 19, 2013 2:09:12 AM

like i said in my last post your next step is swap out the cpu or mother board because that is all that's left.
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a b à CPUs
January 15, 2014 6:14:44 PM

pull out the cpu and have both power connectors hooked up to the motherboard. does it stay powered on?

it wont post of course but it sounds like theres a short in the motherboard cpu voltage regulator or the cpu itself as it stays powered up if you unplug the cpu power cable but when pluged in your power supply detects a short and shuts off like its suppose to.

if it stays powered on with cpu out of the motherboard then my personal view is cpu is fried(shorted inside).

ps be very carefull that nothing conductive touchs any of the exposed cpu pins on the motherboard while its pluged in or motherboard will get damaged
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June 8, 2014 2:40:56 PM

I would love to see this answered, as I have this exact problem. I also have similar system specs, just different cause of problem. I was building a computer for my little brother, when I swapped mother boards, and it hasn't worked since. The new mobo is compatible, and much better than the old one. I don't think it is a psu problem because it is a hefty 750w psu, far beyond what I need.
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