PC won't post sometimes..

[Obi Two Kenobi]

Someone in my neighborhood called me up about a problem with their PC. It won't post sometimes. When you press the power button, the system comes on, all the fans whizz but no beeps and nothing on the screen.
When I press the DVD Rom eject button just as the computer is starting up, the drive ejects and the pc posts and goes to the desktop. Sometimes when I start up the pc, the DVD rom's light don't flash and the drive can't be ejected...

During testing, I ejected the tray at the power up and went into the BIOS. The 1st boot device was set to the CD rom so I changed it to the hard drive. I saved and it got to the desktop. I shut down, plugged out all the cables and in again and powered the pc up. I did this three times and every time it got to the desktop. However, when I tried this one last time, it didn't post again.

Occasionally, the pc pasts post but before it shows the Windows XP loading screen, the monitor just goes to standby mode. (I have tested another screen yes).

Thinking it's a power issue, I opened up the case and disconnected some devices and then powered up. This didn't help.

I took out the Ram and got the beep so there is no motherboard problem/failure.

For no reason whatsoever, I tapped at the PSU a few times while the computer was turned off but the power cables were connected and every time I tapped, the fans (the CPU one included) turned for one second.

I took out the CMOS battery for a while and that didn't help either.

Any Ideas? I'm stumped.

 

[pcgeek11]

I took out the Ram and got the beep so there is no motherboard problem/failure.

This sounds good but isn't a fully qualified test. There could still be Motherboard issues. Look for Bulging and or leaking Capacitors. This sounds like what happens ( or what I have seen in the past ) for this problem.

For no reason whatsoever, I tapped at the PSU a few times while the computer was turned off but the power cables were connected and every time I tapped, the fans (the CPU one included) turned for one second.

This shouldn't happen with the computer off. You very well may have a PSU problem. Swap it with a known good one to test. It could also have capacitor issues.

pcgeek11

 

[Obi Two Kenobi]

This sounds good but isn't a fully qualified test. There could still be Motherboard issues. Look for Bulging and or leaking Capacitors. This sounds like what happens ( or what I have seen in the past ) for this problem.

pcgeek11

Thanks for the reply, I examined the motherboard up close, but alas, no bulging/leaking capacitors. Will try out a new PSU..

Any idea what's the connection between the DVD Rom and booting? Why is it causing the aforementioned issue?

 

[pcgeek11]

Any idea what's the connection between the DVD Rom and booting? Why is it causing the aforementioned issue?

That part is a puzzle... I really have no idea about it except maybe it " changes " something in the circuit when the drive opens the tray as it will draw more current for the motor.

or space aliens???