Intermittent startup

I am having intermittent startup/bootup problems that started happening occasionally but are increasing in frequency. The system was built about a year ago and has been working flawlessly until recently. When the does boot up properly, it works perfectly -- no issues or errors at all. I can soft-start the system multiple times and it will bootup with any problems. But when the system does NOT bootup, there is absolutely no activity or sounds at all (no beeps, no fans, nada except the mobo led is lit). System: Asus P5N-E SLI mobo, Dual core cpu, Windows 7 OS, OCZ 500W power supply. When the system fails to start with the power on button, I have to shut the power off at the back of the PC, remove the plug from the wall, wait a bit and then reverse the steps. That was usually successful in the past but is less so now. (saw this suggestion in the forums) I tested the power supply using a multi-meter and it was producing the proper voltages. I tested the power-on button on the case and it showed continuity whenever the button was pressed (so OK). When the power-on fails, I can see an LED lit up on the mobo, so power is getting that far but neither the psw or cpu or case fans work. When I opened the case, I found the 4 pin of the 20 + 4 pin power plug was disconnected. Not sure when that happened but I reinserted it, hoping for the best, but the problem persists. Tested the mobo battery and it is 3.3V (so OK). Something odd: when I tested the power supply, I left the psw in the case but removed the 20 + 4 connectors and the other 6 pin power connect from the mobo. When I shorted the green and black wire with a paper clip, all of the fans worked -- not sure where their power was coming from -- must be some kind of feedback happening. Don't have another psw or mobo to test with so if anyone has any great ideas I would appreciate your input. Thanks for your help.

 

Welcome to Major Geeks.

Off the top of my head, my first thought is either a motherboard or BIOS problem.

Go to the ASUS website and see if there is a BIOS update for your board. If so, download and install it. If the problem persists and you have an extra power supply around, I'd hook it up to the system to test for an intermittent PSU issue.

Hope this helps.

 

Thanks for your input.

There is a BIOS update but I am always reluctant to mess with flashing because of the potential for screwing something up royally! But perhaps I will give it a try. There is a flash program tool which may make the job easier.

As an aside, I read that sometimes the mobo warps slightly and when cold there are breaks in the welds so a good connection is not made. When warm, a better connection is established and the computer boots up readily. So I let the computer cool down overnight, tried booting -- nothing. Used a hair dryer to warm the mobo, tried booting -- nothing. Then I let it cool down again, warmed the power supply instead -- voila, boots up. Repeated the process, and it worked again. So I'm leaning towards the power supply. Don't have another and so I will have to order one.

Thanks again. Let me know if you get any other ideas.