intermitent boot up

[metrevor]

I am taking a look at a friends PC for him. One day the PC will boot up and work ok the next day it won't boot up and vice versa.

When I went to have a look at the PC today but it would not boot up properley. It does the POST test. After the memory check it detects everything on the ide channels (hard drive, DVD drive and CD re-writer). Then the system hangs. I am left with a black screen and flashing cursor. No changes in either software or hardware have been made to the PC. I have tried reseating the ram (although if it was the ram am I right in saying it would not boot at all?) I have checked all cabling is secure.

 

[Dreamland]

So are you able to get it to eventually boot by restarting it a few times? How fast of a CPU? What kind of hard drive?

 

[metrevor]

You have to leave the PC for a number of hours (not sure how many) before it will start again. For a test my friend left the PC on from about 10 a.m. Sat morning until 18:30 Sun evening so in total it was on for about 18.5 hours. I can only assume from that the ram and CPU are ok as it if was a CPU overheating problem surely the PC would shut down? When I arrived I was able to fully use the PC. I shut the PC down and tried to restart it. I then got the boot up error. My friend says if I come around tomorrow it will start up first time but if you close it down again (even straight away) it will not boot up again. I have reseated the heatsink and give the fan a good clean. It is a Intel 500mhz CPU and I think it is a maxtor hard drive. I know for sure it is 20GB. All cabling is secure.

 

[Dreamland]

OK, so you're saying that when the machine is 'cold' it will boot up fine. Once it starts running, it keeps running. But if you try to reboot it after it's been running a while, it hangs?

Sorry for the questions - I just want to make sure I understand when the problem is happening.

 

[relaksuah]

start from scratch, and put in things one by one, you should be able to know what might have caused the PC to hang. It might even be a hard drive prob/OS prob? ever tried booting up with a diskette?

try disconnecting all drives and taking out all cards except for the display card. isolate the problem from there. if it boots up fine to the point it says No operating system found, it means that the hardware that is currently connected is more or less quite fine. Connect the hard drive and floppy drive after that, and see whether it boots up. Give it a try.

 

[metrevor]

Yes that seems to be it dreamland. I think i will have to get the Pc of my mate and investigate more.

 

[wpfaff]

This could also be a power supply problem. Do you have the equipment to check the power supply?

 

[Dreamland]

It could still be thermal in nature, metrevor. The power supply is least stable when it's hot. The CPU, drive controller and southbridge are most suceptible to voltage fluctuations when hot themselves. It is possible for the whole system to be fairly stable for long periods of time but be unable to reboot when warm - some old servers behaved like this. New power supplies often solved the problem, and were our first choice (we had plenty of spares available to try). We could never solve others this easy and would just give up after swapping out everything else possible and running out of CO2 'freeze' spray. Good luck!

 

[relaksuah]

whoa... did you state you <B>reseated</B> the heatsink?
have you cleaned both heatsink and CPU and reapplied the thermal grease before placing the heatsink back on the CPU?

btw, do take note of the boot up error/BIOS error message. It may help us tell you whats wrong...