Problems booting up! (no video)

[Michael]

I'm trying to fix my mom's computer, but I'm really not very good at fixing computers. Anyhow, one day when turning on her computer, the screen didn't turn on. Everything else works fine (heatsink fan, CD drive, both hard drives, video card fan, lights), but the monitor doesn't display anything. The LED on the front just keeps blinking, so I guess it's staying in the power saving mode.

Here's what I've done so far:

The monitor works, I tested it with another computer.

Next thing I did was disconnect all the drives and the power to everything but the video card, cpu, and motherboard, and took out all but 1 stick of ram. The monitor displayed the BIOS screen thing, hooray! I tried putting the two sticks of ram I took out back in, but then it didn't work, so I took them out again. So I hooked up the hard drives and CD drives, and it still displayed the BIOS (hooray!), but said something about the floppy drive not working (it doesn't have one). So, I hook up the keyboard (PS/2) so I can change the BIOS settings so it doesn't look for a floppy drive. And now the monitor won't turn on again. So I unhook the keyboard and try turning the computer on, and now it doesn't work. So, I changed the RAM slot. I turn the computer on once, and it doesn't work. I turn it on again, and it does work. So I hook up the keyboard, won't let me actually input anything, so I turn it off and turn it on, and it doesn't work.

I am so confused. It just seems random to me, but maybe someone here knows what's going on!

Quantux

PS/2 keyboards are not hot swappable, and plugging one in while the mainboard has power could result in a short. Not too likely, but you never know. It's safe to leave it plugged in while troubleshooting (or better yet grab a usb keyboard). Sounds like 1 or more bad sticks of ram. Try each stick, by itself. then try 2 of them, then try all three. Another possibility is bad vid card. If theres onboard video, pull the card and use that. Yet another possibility is bad power supply, not supplying the correct volatge for all devices.

And as always, before touching anything inside the case, unplug it, turn the switch on the power supply off (if there is one) and wait 30 seconds.

[Michael]

I tried every combination of RAM just now, only 1 stick will get the BIOS to come up on the monitor. I've tried 2 different keyboards now to try to change BIOS settings, but the keyboard seems to cut out after a couple of seconds (or the keyboard doesn't work at all), so I haven't been able to do hardly anything. Happens with both a PS/2 keyboard and USB.

There doesn't seem to be any difference between onboard video and the video card. Any idea what I should try next? Or any idea what's wrong?

edit: Also, once or twice, the BIOS has come up on the monitor, but then the monitor has gone back to not displaying anything after a second or two, with the computer still running.

mightyjongyo

power supply failure? im not really sure how to test that without swapping in a new one though. it could be that it's unable to maintain the power output or something like that.

[Michael]

hmm...I guess I can try convincing my brother to let me steal his power supply for a day to give it a try. I'll let you know how it goes!