Computer doesn't boot occasionally

Hi,

Yesterday I've bought a new PC. It has an i7 3,5 GHz processor, a Gigabyte GAz77x-UD3H mainboard, a Nvidia 680 GTX graphics card, 32 Gb of ram, a 240 Gb SATA and two 2 Tb Harddisks, a 750W power supply (Corsair), a blu-ray writer. The first time I've tried to boot the unit, I was unsuccessful. The lights on the case were lit but there was no harddisk. Also the monitor didn't wake up. I have resetted and got the same results. As the graphics card has 2 DVI inputs, I've thought that maybe one of them was inactive, so I've plugged the DVI to the other port, resetted and the computer booted normally. These events happened yesterday. Today, when I turned on the unit, the same thing happened. I've followed the same procedure and it booted again. However one thing grabbed my attention: When the computer doesn't boot, there is no beep coming form the BIOS (I haven't paid attention yesterday), so I don't think the problem is with the graphics card. After booting I did a shutdown and restarted again without a problem.

This is a new unit, so I am unhappy . Where do yo think the problem is? How can I troubleshoot it?

 

Hi DavidGP,

Thank you very much for the answers. I'd like to give you a few more details. I didn't build this PC, it is pre-built. I've contacted the manufacturer by phone, told about the problems. They have guided me over the phone to make a few changes in BIOS, unplugging USB devices (external sound card), unpugging the blu-ray driver, shutting the interruptor of the PSU, using a different wall plug, etc. However none of these things helped, I still have the same problem and it got worse. Now, I am able to boot only 1 in 13-15 times. When it boots, everything is working perfectly, I get no error at all, so I'd assume that there are no loose connections. I'll have to bring the unit back monday but it is quite heavy and the shop needs a 2 hour trip so I'd be much happy if I could solve it myself.

I also have removed the side plate of the tower, so I have access to the mainboard's LED. I don't think it is a boot disk problem, because there are no errors on the screen when it doesn't boot. In fact, the screen stays in stand-by mode. Generally, when I turn the unit on, the LED shows 3-4 numbers, the last one being 96. The debug led codes in the manual tells me that 96 is one of the regular boot codes (it is not an error code) and the description is "Assign PCI device resources". I assume that the boot sequence stops when it has to "assign PCI device resources". Sometimes, when I turn the unit on, I hear 5 or 6 short beeps, followed by 1 or 2 longer ones, and the LED code stops at D4, which is an error code according to the manual ("PCI resource allocation error. Out of Resources"). If the unit stops at 96, I have to press the power button for 6-7 seconds to shut it down, but if it stops at D4, touching the power button for an instant is enough to shut it down. After rebooting 15-20 times, I have been able to boot normally now. The LED code is A0 (don't know if it is a zero or the letter O). The unit is working for 8 hours now without a problem but I don't dare to shut it down as I suppose it won't boot again. Resetting is no problem as it boots normally.

I did some research on the forums. Some people claim that the problem was due to a faulty mainboard, which, when replaced, worked without a problem. Some people claim that the Corsair PSU may be incompatible with the main board (how would that be possible?).

 

An update: I've brought the unit to the manufacturer. Surpisingly, the system booted 9 in 10 times without a problem (at home it was just the opposite), however it gave the same 96 error when it didn't boot. I suppose there might be a voltage problem at home but this doesn't explain the same error happening, while less frequently, at the manufacturer. They used another PSU (xilence 750w) but the same error happened again 1/10 times. They updated the BIOS but it didn't help (now they get e b2 error and the system doesn't boot - maybe a flashing error?) They told me that they would order new ram sticks to try on board.

The manufacturer told me that newer PSU units with high capacity, which recieve bronze or gold certification, are more sensitive to voltage fluctuations. This seems odd to me. Isn't a good PSU supposed to deal with this kind of voltage problems?

 

Another update: The manufacturer replaced the mainboard with another one (now I have an ASUS mainboard) and now everything works perfectly. Bad mainboard or incompatibility issue maybe?