PC will not start.

[p51d]

Hi all,

I need some help to find out why my PC will not start. The problem with the PC not booting was not caused by me upgrading or changing anything. It just started happening.

The cpu is a Celeron 533, mainboard is about 12 months old, and I've had no problems with it until now.

Problem:
The CPU fan will start on power up, and then it all shuts off after about 5 seconds. The PC will not begin POST or anything.

I have tried taking out the DIMMS, periheral cards etc., even the mainboard out of the box to see if this enabled the PC to boot to no avail. I have also slotted another CPU to see if this was the problem. No difference..... same as above, not booting.

I can see no obvious damage to the mainboard. Since the problem started it has booted on 2 occasions after being left for a few days, the last time the was some message about a CMOS checksum error.

Can anyone tell me if there is anyway I can fix this problem or is the mainboard just trash now? I don't get it... What's gone wrong?

 

[edfair]

Generally it is a problem with the power supply shutting down. Either because the power supply is defective, or because some component attached to the power supply has started drawing more current than previously. You might try pulling power connection to all except the board and see if it gets to the os fail point.
And power supplies can sometimes become less tolerant of near 100% draw. Ed Fair
efair@atlnet.com

Any advice I give is my best judgement based on my interpretation of the facts you supply.

Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[FoxStudent]

have u tried clearing the cmos and possibly getting a bios upgrade/? let me know if this helps
bikergal@eircom.net

 

[hotfusion]

I would go with the power supply as first suspect. If you know anyone with an interest in electronics, you may be able to get them to test the unit - check voltages under no load and heavy load to assess regulation. This type of supply is known as 'swich-mode': Without going into any more unnecessary detail, they have some fairly complicated control circuits which could cause this shut-down effect under fault conditions. My suggestions are what I would try myself. If incorrect, I welcome corrections to my knowledge. Andy.

 

[p51d]

I have got it going finally !!

I have previously tried using a power supply from another box...... no joy. I also tried clearing the CMOS a few days ago before I began this thread ... again no luck.

Resolution (maybe)?:

As I described in my initial post.. the PC will try and boot after being left for a while (crazy machine?).

I tried booting it up again list night .. and recieved the "CMOS checksum error" message again. I went into the Bios config and reset everthing. PC is now booting normally.

I'm still not exactly sure what caused the problem, or if it will come back. The PC is booting at the moment with a celeron 466 cpu, not the original 533.

Can anyone tell me if the "CMOS checksum" message is normal if you clear the CMOS?

 

[bhunt]

I have almost the same problem except my fans stay on. I also have not received a cmos error. I did everything suggested on this forum and other places including replacing parts to no avail.

After I leave it alone for a day or so when I hook everything up it will work fine. The last time this happened I got it to boot then did not reboot for a week in case it wouldnt come on. The other day I shut it down as a test and it started its bad ways again.

Like you when it does boot it boots at 500 mhz instead of 1.2 gig which I then change in bios.

If it happens to ya again let me know what you do to fix yours and I'll keep ya posted on what I do to mine.

Ben

 

[edfair]

If the fans stay on , the PS hasn't crowbared, which is what was probably happening on the original post. I've also seen the problem with the power switch set at 230v. I've done it myself if its any consolation.
Slower the processor , the less power expended. If a questionable PS, then may work slower but will probably eventually fail.
Checksum error is probably unrelated.

Bhunt,
Fans blowing signal 12v is good, if it hasn't crowbared the other voltages are probably good, except ATX power supply 3v can go away without killing the others. Your symptom is of power good failure, bios not processing, processor bad or needing reseating, ram needing reseating, video not processing or any of several other things like a crystal failing. Ed Fair
efair@atlnet.com

Any advice I give is my best judgement based on my interpretation of the facts you supply.

Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[p51d]

Edfair

Thanks for your comments above. re: "power good failure", this is probably correct. This would cause the PC to shut itself off ? But why?

I switched almost every removable component I could, including a different (newish) PS and cpu (the 466). On every occaision the PC still switched itself completely off after 5 seconds without going to POST.

This will probably start happening again I bet.

 

[edfair]

Haven't checked for later PS-MB combos to see what power good does. Earlier failure shut off the processor clock so nothing worked. Slow coming up allowed some processing then killed processing, but didn't turn power off.
ATX form factor? If so, does it have a continuous power supply fan? Does it shut off when the CPU fan shuts off. If PS fan goes off, then total power lost. If PS fan stays on then M/B is shutting it down, either by failure of power off circuit, problems in power management, or bios going into left field. Ed Fair
efair@atlnet.com

Any advice I give is my best judgement based on my interpretation of the facts you supply.

Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[p51d]

Alas ... the problem returns.

 

[ajax288]

Hi,

I have the same problem with a socket A mobo.

When i push power on, it stays on for 5 seconds and then shuts down. Same as if I were holding the power button to make it shuts down by myself. So I tought it coul be a short. I took the mobo out of the case and put it on a no-static environnement. I plugged a switch on the 2pins power switch. I started it and keep clicking on the switch so the button wont be hold for 4-5 second. The result: The computer started and booted. I tried it with different power supply and different switch button to make it sure that those were not the problem. I think that click on the switch resets the 4 second counter for shut down. I don't know where exacly is the bug but it's in the mobo. I tried the trick on 2 other mobo like that one and no problem. They were not defective.