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View Full Version : Computer automatically powers on and has no signal/post


zrhodus
03-08-2006, 02:57 AM
PC Specs

AMD xp 2600+
1.5gb pc 2100 ddr
80gb hdd
Geforce fx 5200
agp 4x

As you can tell its no new pc, in fact its probably now 3 years old and now suddenly its not working. I am stumped with this as of late.

I will start by saying I have transported the pc between my dorm room on campus and my home several times since the beginning of the school year. I fear I may have somehow shocked the pc with static in my car for the following reasons:

When I returned to the dorm with my pc it powered on as soon as the power cable was hooked into power supply. It has never done this before, but I assumed I had just accidently pressed a button. I then noticed that the pc was not loading at all..there was no hard drive noise or blinking of the hard drive led. The cd and media reader lights burned steady however.

Fearing the black screen of death I held down the power button for 5 secs or so manually turning off the pc. It then came back on on its own, making the only way to turn the power off with any finality to remove the power cord from the back.

I haven't made any significant changes to the system in the last 3 months or so but I still started trying to figure out the problem by eliminated drives and accessories.

At the point I'm at now I've got the Mobo on a piece of cardboard, hooked into the power supply, with 512 mb of ram, the cpu and the heatsink. The onboard video seemed easier to use for troubleshooting purposes. The pc still will not boot, and does not beep, or give the monitor a signal, or any signs of posting for that matter. I have tried moving the CMOS jumpers as well as taking the CMOS battery out for 10 minutes or so, but this did not help the situation. The computer remains idle on boot attempts.

The problem is not the memory because the memory worked fine in my roommates pc, which uses faster ddr, however the memory did step down and run fine on his pc.

I have not seriously considered the power supply because it does seem to be supplying power to the board and the board will still..temporarily shut off when the two power tips are grounded wouth a screwdriver.

So after doing this I've come to the conclusion that either my CPU or mobo is bad. I have not considered the CMOS battery because I would assume I would get some sort of life out of the machine even if it was dead (POST). I do not know or have a way of determining from here if its the cpu or the motherboard so I thought I would ask some more skilled computer people what they thought. Thanks in advance for any help :)

ski
03-08-2006, 10:25 AM
Disconnect the main power cable from the computer, disconnect the power-on button's wires from the MB's terminals, and reconnect the main power cable. If the system starts up without pressing the front panel power button, then the MB may be bad.
If the system does not start up after reconnecting the main power cable above, then start the system with the screwdriver. If the problem goes away, then the button assembly is probably bad.

zrhodus
03-08-2006, 11:05 AM
Yeah I tried that last night. I had to use the screwdriver to cut the power off because the power starts as soon as the motherboard gets power from the power supply when I'm running the mobo outside of the case. Also I do not get any post or cmos screen when I'm running the motherboard/ram/cpu/vid on its own. I'm pretty sure it my mobo at this point. The only other option would be the cpu, which I hope is not ruined.

I guess my next question would be if my motherboard went bad could my cpu be bad and if so would a bad cpu ruin a replacement mb? :confused:

Whyzman
03-08-2006, 11:39 AM
Do you have another power supply you could swap out? A new button battery might not be a bad idea...they may last more than 3 years, but who knows how long it might have been in the rig until it was actually put into use. Some companies do use a piece of plastic between the contact that effectively keeps it out of use until you remove it...

However, I think I would do that as part of routine maintenance...especially, since there's no life in the thing at all right now.

How does the heatsink look, all gunked with dust? Or, do you perform routine maintenace?

zrhodus
03-08-2006, 01:26 PM
The processor and heat sink look fine. I routinely vac and air dust the thing out to remove dust. I don't see any burnt up capacitors on the motherboard and no real gunk on the processor aside from the thin layer of poxy stuff. This is kind of why I'm stumped, I haven't done anything out of the ordinary to the system and its just not working..at all. I may try my roommates PSU later with his consent..and yeah I will replace the battery. I was just thinking that even if the battery was dead I would get some sort of life out of the thing aside from idling fans. Can a bad PSU do something like this?

Whyzman
03-08-2006, 06:04 PM
At this level of hardware troubleshooting the easiest way is just swapping with known working components. The basic stuff kinda piggy-backs on each other and without the bench equipment to actually isolate and test the individual components...swapping is the easiest...

You might want to try reseating all the stuff...IDEs, power, even the RAM...just to make sure everything is tight.

The thing about PSUs is that there are different voltage rails. It might be a 5V that handles the momentary power switch igniting the PSU and communicating to the other rails to send forth their energy... If any of the other rails are kaput, you might see some action but not what it takes...

Swapping if you can would definitely help...