I have just finished building my first homebuilt computer. The computer started up the first time and everything seemed fined. I ran the system approximately 30 hours over 4 days without any problems. I then left town for about 5 days and the computer was unused. Upon arriving back, I started the system and it ran fine for approximately 20 minutes before abruptly shutting off. Since that time, the system has had trouble passing POST. There seem to be three scenarios that are occurring now.
1) The system will turn off immediately after turning on and refuse to start again. In this case, the memory loading LEDs stay on. The system shuts down faster than I can read a POST code off the mobo. When this occurs, the only way to attempt to start the system again is to remove power to the motherboard.
2) The system will turn off after about 1-2 seconds and continually attempt to restart on intervals of about 5 seconds. When the system shuts off, none of the LEDs are illuminated. The POST code display prior to shutting off is C1h, which according to the mobo manual is detect memory.
3) Occasionally, the system will start up normally. This happens about 10% of the time.
1) and 2) occur with approximately equal frequency.
The only thing that I changed before and after my trip was that upon arriving back, I installed a second monitor. However, I have tried several monitors configurations (including completely removing the video card) without any affect. I have noticed a few strange things about the video card that may or may not be related. I was noticing red dots on dark backgrounds. I have read that this may be a sign of dying memory on the video card (the video card was purchased used). Another thing that I have noticed is that there seems to be some power provided to the board by the DVI connectors. When two monitors are powered and connected to the video card, the 7-segment delay for POST codes is illuminated, even when I unplug the PSU. The illumination is not a bright as when the board is powered on, but it is clearly visible. This does not occur when only one monitor is plugged in.
I have also tried many configurations of memory without affect. One thing I noticed is that the memory is spec'd for 1.65V however the mobo was automatically providing 1.5V. After the problem started occuring, I tried increasing the memory voltage without affect.
The hardware for my system is
Mobo: Gigabyte ga-x58a-ud5
Video card: Gigabyte Nvidia 8600gt GV-NX86T256D
Memory: Corsair Dominator 6GB (3x2GB) DDR3-1600
PSU: Corsair 750TX
CPU: Intel i7-920
Does anyone have any suggestions? Is the mobo defective?
I have noticed that when condition 1) occurs, the south bridge overvoltage LED on the motherboard is red immediately after turning the system on, indicating high overvoltage. Is it possible that the video card is causing this?
I have removed the video card and I don't seem to observe 1) anymore. Now 2) Prevents the system from starting. I have noticed that when the system shuts down like 2), the north bridge temperature LED is red indicating that the north bridge temp is greater than 80C. This is occurring even on a cold boot so I doubt that the temp is actually greater than 80C. Is there something wrong with the motherboard?