My sister bought a Dell Optiplex GX280 off of Ebay. It worked fine for about 2 months, but then after a while it shut off. Now you see this isn't shutting down, the display turns off, or should I say the monitor light turns orange, but the power button on the case is still green. I hooked up a keyboard with backlit keys, and when this happens the keyboard lights flicker.
The HDD LED Activity light shows that the HDD is still functioning and everything inside is fine nothing smells of burning, or anything. The logs on both bios and windows show nothing significant apart from a Keyboard Failiure at boot. I've tried swapping and removing RAM chips, with same results. I have tried many things.
It will sometimes boot up fine and stay on and working perfectly for hours but then others it will not work at all or work for 10 mins and then stop. Totally random intervals. I used to be able to get into safe mode on the computer but that doesnt work anymore. But lately it does this within a couple minutes or less.
I was told by the company that sold it was the hard drive. So she went out and bought a new one. I put that in and all was fine during the hard disc formatting. Then began the windows install and started doing same thing during the install. Now, I slept on it, and try to turn it on in the morning, now it does this withn seconds.
I am thinking possibly the CMOS Battery but it is unlikley seeing as there are no erros in the boot logs.
i think your right about the CMOS battery not being the problem. Also i truly doubt that the hard drive is the problem. Hard drives have a pretty distinctive way of preventing the system from booting when they get corrupted.
Based off of what you have told me, i am fairly certain it is not the CPU, motherboard, hard drive, or RAM. I believe your problem is the Power supply. Like you said if one of the major components like CPU, RAM, or motherboard died you would be able to find an error report. So i think your PSU has degraded so to speak to the point where it half way runs your computer in this comatose state.
A similar guess would be heat. If your north bridge, south bridge, or CPU were seriously overheating it would cause you some problems. However, again i would image you could find some kind of error report in the bios.
My recommendation is if you have another desktop computer (and someone who knows how to build computers) swap the PSUs out and test the rest of the hardware. if everything works then you just need a new power supply which can be had for $50 or 60 US.