What can cause motherboard not to POST

[farmercal]

Background information: System components only about 8 months old.
Motherboard: Aopen AK77 Pro
RAM: PC2100 Micron 128MB, and generic 256MB
HD: Maxtor 7200, 40GB
PS: 300 W
CDROM: Liteon 52X
CDRW: Acer (old one but works)
Video Card: ATI Radeon 8500 LE/128 MB DDR RAM
OS: Windows XP Pro

Now here's is the problem - System boots and POSTs just fine after system has been off for about two or three days. At the beginning it will POST everytime I restart or power down and reboot. After a day or so it will not POST anymore. In this not POSTing state I removed the video card, RAM, disconnected all the drives just to see if it would produce a error beep to no avail. I have run with either stick of RAM at different times but got same result. When I measured all the voltages at the end of the connector on the MB (when everything was running) all voltages measured properly. Could this be a PS or CPU problem? This is the thired MB with the exact same problems (doubtfull that 3 MB could be flakey in same manner). Any suggestions? Sorry about the long post but I figured it would be better lay out the whole picture at one time.

Cal

 

[alchemist]

Is the power supply AMD approved. I had a similar situation once.....my computer would run for days, and then then when i restarted it, it took many tired to get it to work....changed out the power supply and havent looked back since.

 

[farmercal]

Yes the PS is AMD approved. It it the one that came with the Fong Kai 320B. It is an Enhance 300W ATX Power Supply Model No. ENP-0730. It is suppose to be good up to 1.3GHz and I am only running a 900 MHz CPU.

 

[Kipper]

Try reseating CPU...check your manual for beep codes on motherboard. You'll hear beeps come out of the speakers if there is a problem, usually.

 

[alm4rr]

might be heat, youd have to check

 

[Gamerguy68]

Could be power fluctuation issues. Are you using a UPS or line conditioner?

 

[MithShrike]

I agree with alm4rr about the heat. If you have memory that's failing under heat you may want to replace it. Minimum for POST as we should all know is CPU, Memory, and Video Card so if any of these fails no POST. I figure you might have memory that fails under high heat.

 

[farmercal]

It's not a heat problem as my temps are around 35 and 37C most of the time. I have replaced the CPU with a 800 MHz Duron and everything seems to be working for now. Of course with the other CPU everything worked for about three days and then it quit. I think I recall when looking at the BIOS settings (computer health) that there was no CPU RPM being monitored with the previous CPU and HSF. Perhaps the connection of the CPU fan wasn't making good contact and couldn't measure the RPMs. I have heard somewhere that a motherboard won't POST if it can't sense the RPM of the CPU fan. We will see. Thanks for all the inputs!