Troubleshooting a dead PC

[Missing Ghost]

My parent's PC stopped to work a couple days ago. It wouldn't start. That is, the PC powers itself (the fans are spinning), but there is no BIOS screen at all.

I would like to know if there is a possibillity that it's not a dead motherboard.
Here is what I did to troubleshoot.

-Unplug optical drives and hard disk drive and remove non-essential expansion cards.
-Replace the PSU with a known good PSU (I tried with a Seasonic S12 500W)
-Replace the RAM with RAM that works in another PC
-Replace the video card with another good one
-Reset the CMOS

Now all I have is the old mobo with the old CPU, with the good RAM, video card and PSU and it still doesn't work.

There is no speaker beep either.

One thing I find odd is that the power led on the front is not lighted up.
Another odd thing is that it seems to be in an infinite reboot/reset cycle. When I had the optical drives plugged in I could hear them restarting every 5 seconds. Also the hdd controller led flashes every 5 seconds as the PC restarts.

 

[jhayx7]

I would say if there is no video and the video is known good, dead CPU.

 

[stevf]

if it seems to be rebooting, the switch may be bad, stuck in the contact position. To test this remove the plug for the switch from the mobo and short the two pins you just removed the plug from with a screwdriver for a second and see if that makes a difference. The switch may be broken or gummed up causing it to be constantly closed which will make it reboot every 5 seconds or so.

If that is not the case, sounds like it is either the mobo or cpu. Did you check voltages from the PSU, just to make sure one isnt out of tolerance?

 

[Missing Ghost]

Originally posted by: stevf
if it seems to be rebooting, the switch may be bad, stuck in the contact position. To test this remove the plug for the switch from the mobo and short the two pins you just removed the plug from with a screwdriver for a second and see if that makes a difference. The switch may be broken or gummed up causing it to be constantly closed which will make it reboot every 5 seconds or so.

If that is not the case, sounds like it is either the mobo or cpu. Did you check voltages from the PSU, just to make sure one isnt out of tolerance?

I tried to unplug the power/reset switches, it didn't change anything.
I did check the voltages of the PSU, it was like 4.9/12.5V, but that shouldn't matter since I'm already trying with another PSU to be sure.

 

[GalvanizedYankee]

http://www.badcaps.net/Ident/ Read it well.

Is it a PC Chips board? What kind of board and how old? After 5 years one can expect issues with a cheaper board.

 

[Missing Ghost]

Almost 2½ years old DFI LanPartyUT NF3-250. It's built with good capacitors and one of the first things I did was to inspect each of them... they seem ok.

 

[Jiggz]

Dismount the mobo, remove and clean the cpu hsf and also remove the CPU to make sure it is clean and properly installed. Ran the mobo from outside of the case with minimum peripherals. No hdd is required just to see if it'll post.