Is it the mobo or the CPU ? How ? 2

[vanessa100]

My desktop PC suddenly conked out after 4 years running really well ( Mobo Gigabyte GA-EP45-UD3L , Dual-core Intel CPU, DDR 2 RAM, Windows 7 ) . Now, each time I turned it on, the PC started for 3 seconds then shut down ( i.e even before self-test period ! ).

1) At first, I thought it might be a Power supply issue so I took it out and installed it in another PC . The verdict : no problem with the power supply !

2) So the problem is the mobo or the CPU ?

My question : How can I tell if it is the CPU or the mobo issue ? Is there any quick test to tell the difference ? It would be a disaster if I blindly replace the mobo and then later find out it is the CPU that needs to be replaced !!

Please comment & provide guidance . Thanks,

Best regards,

 

[hairlessupportmonkey]

This almost seems like the CPU is overheating. have you removed the heatsink? Will be worth cleaning it re-applying thermal paste and try again. Either that, check the capacitors on the motherboard, especially around the CPU area, they tend to swell and blow out the bottom and dry out.

ACSS - SME
General Geek

 

[vanessa100]

Thanks for your quick response ...

I started the PC from cold ( i.e. the PC was off for several hours ! ) ...

I wonder why the CPU could be overheated in just a few seconds to shutdown the system ?

 

[goombawaho]

First, you need to see that the CPU FAN is turning properly. That trumps everything (thermal paste) in terms of causing overheating. Next, if it IS turning properly/quietly, look for junks of dust and/or pet hair in the heat sink fins.

If clogged, I would remove the heat sink and clean it out really well then clean off the CPU and the bottom of the heat sink (remove thermal paste) and re-apply thermal paste, then re-mount heat sink.

 

[vanessa100]

I cleaned out the internal of the PC with a compressed air bottle and everything is squeaky clean inside (including CPU fan + motherboard ) ... As I said before : everything ran OK for about 3 second ( CPU fan , Power Supply Unit fan , internal fans all running) then complete shut down without any beeps !! ! . Is there any indication that the mobo or the CPU is bad ?

 

[rmvrents]

Gotta be the power supply...

 

[vanessa100]

Eureka !!

It's just incredible how I finally solved this start-up problem!

To make sure it was not a short-circuit issue of the mobo , I removed the mobo out of the box, then connect just 2 main power cables to it .

When I switched on the PSU (Power Supply unit) , the mobo responded as before : starting then shutting off within 3 seconds ! But I noticed that this occured even before I pushed the power button on the PC Box !! I thought the Power Swich Button on the PC Box might be the problem .

To test this hunch, I brought in my old PC , unplugged its power switch cable and plugged this cable into the problematic mobo . Then I used the start button of the old PC to switch on the mobo . Everything worked like a charm : all fans running, no more shutting off !!

So it was the power swith that caused all the problem !! Case solved .


Thank you everybody ....


Vanessa100

 

[vanessa100]

I just found this review... My problem is not that uncommon after all !!


Shut down right after start up fix. Use DeoxIt D5
By
R. W. Milyard "GearJunky" (Fort Mohave, Arizona United States)

This review is from: HDE Power SW Motherboard Cable for PC Power Switch Button (Electronics)
If you are going nuts trying to figure out why your computer shuts down right after
start up and have been replacing power supplies, graphics boards and ram and reconfiguring
your set up and the thing still shuts down, REPLACE or DeoxIT THE FRIGGING SWITCH!

You can also (with the computer power turned off) cycle the switch a few times just in case
the switch spring is just hanging up, and you should ALWAYS do this first BEFORE replacing a switch.
Also, you can spray a little DeoxIT D5 into the switch (take the cover off the front of the workstation)
and (again) cycle it a few times.
These things have a limited life cycle before the spring inside will start to hang and hold the momentary switch closed and your CPU will go nuts trying to turn off and turn on all at the same time, and you get the dreaded "Overclocking Failed" Press F1 or F2 message the next time you get your computer started again.

This is a good replacement switch, as I used it for about a year and it started to hang as the original did until
I used DeoxIt on it, and is working just like new now. (Also fixed the original switch this way) "

 

[goombawaho]

Good job. With startup issues like that, it could be anything from motherboard, CPU, power supply, or power switch. Of all of those, I've only ever seen ONE switch behaving badly. Also, the switch can either be dead (electrically) OR the little front push button not making contact with the switch (mechanical).

The easiest way to troubleshoot the switch (for others) is to short the motherboard pins manually with a small screwdriver across the pins marked PWR. You obviously have to be careful in this process.