PC powers up but won't boot. Not even post screen!

[dazzaman]

Hi, a PC (Compaq/HP running Vista) I'm working on won't boot nor display the POST. Fans, HDD, etc power up but not a hint of any onscreen activity.
Monitor is good & display settings are fine.
Can access HDD using another power source.
Have tried motherboard in other boxes, nothing happens.
Tried with PCI cards...nothing.
Please help!

 

[r-sky]

Looks like you narrowed it down... Motherboard in anther box - no go. Either cpu or motherboard - I bet on the board

 

[jsc]

Fans, HDD, etc power up but not a hint of any onscreen activity.

How do you know the PSU is good? Did you test it by replacing the one in the dead PC with a known good one?

Just because it looks like everything powers up does not mean everything is. All you are seeing is the system responding to the presence of 12 volts. Unless you have tested everything, you do not know if the 3.3 and 5 volt outputs are present. And you do not know if the PSU control signal, "PowerOK", is present.

Can access HDD using another power source.

Another indication of a possibly bad PSU (or motherboard); the HD works elsewhere.

Have tried motherboard in other boxes, nothing happens.

This would seem to indicate a bad motherboard - if you are absolutely certain you made no mistakes when you installed the suspect motherboard in another system.

For the first step, a more reasonable troubleshooting approach when you have more than one system is to pull a known good PSU and use it to test. This is good for two reasons. First, a failed PSU is the usual suspect when a computer suddenly stops working. Second, it is easier to do than removing a motherboard.

Your problem may indeed may be the motherboard.But until you verify that you do have a working PSU, you don't know for sure.

r-sky is right about the CPU. CPU failures are very rare.

 

[Jonathern]

I had the same issue with my computer all lit up ran but no screen, I learn't that my CPU isn't supported by my mobo double check yours hope it helped?

 

[dazzaman]

Cheers fellas

Have tested with known good PSU's, no changes whatsoever so yes...I am reasonably convinced that it is the mobo. Will let you know when I finally put it in!

Thanks for the helpful comments and tips.

 

[dazzaman]

How do you know the PSU is good? Did you test it by replacing the one in the dead PC with a known good one?

Just because it looks like everything powers up does not mean everything is. All you are seeing is the system responding to the presence of 12 volts. Unless you have tested everything, you do not know if the 3.3 and 5 volt outputs are present. And you do not know if the PSU control signal, "PowerOK", is present.


Another indication of a possibly bad PSU (or motherboard); the HD works elsewhere.


This would seem to indicate a bad motherboard - if you are absolutely certain you made no mistakes when you installed the suspect motherboard in another system.

For the first step, a more reasonable troubleshooting approach when you have more than one system is to pull a known good PSU and use it to test. This is good for two reasons. First, a failed PSU is the usual suspect when a computer suddenly stops working. Second, it is easier to do than removing a motherboard.

Your problem may indeed may be the motherboard.But until you verify that you do have a working PSU, you don't know for sure.

r-sky is right about the CPU. CPU failures are very rare.

Thanks for the excellent tips. You make some good points, I'll try them.

 

[dazzaman]

Best answer selected by dazzaman.