Computer Turns on by Itself, No BIOS

Golden Leg

I come to you with yet another problem.

My computer was running well. Two days ago, I turned off my computer. Several hours later I went to turn it back on. The fans revved, the lights turned on, the fans continued to rev, the BIOS never showed its face.

When I say rev I mean run at a higher speed than normal. Normally on start-up my computer would always run the fans at a higher speed for 3-4 seconds, then the motherboard would beep and the BIOS would appear onscreen. Not anymore.

This problem occurred once before, about three years ago. I solved it then by disassembling and reassembling the computer.

I've completely disassembled and reassembled the computer two times now. The first time I did this the computer started up normally, but the mouse and keyboard did not respond. When I restarted the computer it failed to boot the BIOS and I was back to square one. After the second disassembly and reassembly my computer continues to have this problem, only now it will turn on as soon as I turn the power supply on, not when I hit the power button the case.

What could be going wrong?

Carnarvon

Try popping out the lithium battery on you motherboard and leaving it for 30minutes. Put it back in and see what happens. Past that, you might have a short on your board(very likely if your case is sub-par); try putting in some standoffs.

Golden Leg

I popped out the CMOS battery (CR2032) and tested it with a multimeter. It was reading 2.8 V versus the advertised 3.0 V. Is this a big enough difference to warrant a problem?

Golden Leg

Here's another bit of juicy information. I haven't had time to remove parts and run the computer with just the motherboard and CPU unit to test them, but I have noticed something strange.

Like I mentioned before, the computer will turn on as soon as I turn on the power supply. Interestingly enough, the power switch will turn the computer off after a few second, however, the power switch will not turn the computer back on!

Carnarvon, you mentioned a short being a possibility. I have had the motherboard secured in the same fashion for the past 3.5 years. It is screwed into all the places it should be, according to the case manual. What would cause a short so spontaneously, and will this permanently damage the motherboard?

stigweard

The most likely candidates are a bad psu or a bad motherboard. I'd start with the psu as they are cheaper, require less effort to swap, and it is good to have a spare around anyway.

FingerSlut

is there a pc speaker plugged into your motherboard correctly?

Golden Leg

My motherboard didn't come with a PC speaker. Will any one do or are some better than others?

FingerSlut

any will do, a pc speaker will emit codes like obd2 would on a car.

DiannaoChong

If your motherboard is new enough, plug in speakers and it might just tell you whats wrong, or put beep codes through those.


Anything fucked with the power switch can be the PSU, or a wall outlet problem. I had a computer case where if it was plugged into a socket with bad grounding, touching the case would shock you, and turn the computer on.

Golden Leg

Well, folks, I found the time to look at my computer, and discovered some interesting things.

My motherboard doesn't use a PC speaker to communicate its thoughts. It uses an external USB bracket integrating four diagnostic LEDs. When I boot up the computer, the LEDs are all red. According to the motherboard's manual, "the D-LED will hang here if the processor is damaged or not installed properly."

I'm a bit boggled about this. I was under no impression that my CPU was failing. Do I take my motherboard's word for it?

EDIT: Some background information: I have never cleaned and changed the thermal paste between the CPU and heatsink, even when I removed the CPU and put it in a new motherboard. The CPU is four years old.

Satsumomo

Computers turning on as soon as you connect them to the wall are most of the time because of a bad motherboard. It's error code must be bogus.

Golden Leg

So would I be well-advised to begin investing in a new computer?

The motherboard I have is a socket 939. It's only two months old; I bought it from a company in China as a replacement when my last motherboard went south.

Beazle

Check the tops of the capacitors on the motherboard. I've had a few 939 boards with bad caps. MSI had a whole lot of boards that had defective capacitors on them. I have fixed a few Dell machines that would do what your system is doing and it was bad capacitors.

FingerSlut

Golden Leg wrote: »

So would I be well-advised to begin investing in a new computer?

The motherboard I have is a socket 939. It's only two months old; I bought it from a company in China as a replacement when my last motherboard went south.

You must be missing a step since you fixed it earler by reassembling the components. Remove the heatsink and cpu, inspect the parts and be sure you dont forget anything important when you put it back together.:P

Golden Leg

I sort of fixed it earlier. The computer booted, but then didn't respond. When I restarted it, I was back to a borked computer. I've set up the computer outside of the case and meticulously gone over it to make sure everything is plugged in correctly, and this is the case. I can take a few pictures and post them online; maybe you guys can see something I can't.

Golden Leg

And I checked the tops of the capacitors on the motherboard. They all appear to be in good condition. At least, the tops aren't blown off.