No voltage from PS_ON when power cord is plugged = dead motherboard?

[giandroberto]

Hello guys! I'm at a loss here with a < 2 y.o. desktop build that has just yesterday started to not get any power at all. No fans spin, case LEDs don't turn on, no beeps.

Speaking of LEDs, a green PWR_ON LED on the board stays constantly on while it is hooked to a powered up PSU. All other onboard LEDs stay unlit.

I was sort of hoping it was just a problem with the button, and this is one of those motherboards that has a tiny power pushbutton on the board itself, so I went ahead and tried that: no deal.

Then, I proceeded to test the PSU by itself with the tried and true paperclip method and, sure enough, it's still capable of turning on!

Next, I started removing everything that was connected to the board except for the CPU, its fan and the speaker. Still no sign of life...

Took out the CMOS battery, made sure it still read around 3V with the multimeter, and put it back. No luck.

Finally, I stumbled upon something suspicious: I flipped the motherboard over, tried to probe the back of the PS_ON pin alongside a ground pin with the cord plugged in and the PSU powered on, and I got nothing. It was supposed to read something around 3~5 V even with the PC turned off, right?

What is likely to be the cause of this? Has the board suddenly gone faulty? Or can something else be the culprit?

Any help is most appreciated, thanks a bunch!

 

[cin19]

Next, I started removing everything that was connected to the board except for the CPU, its fan and the speaker. Still no sign of life...

Because you did test the PSU with paperclip method, that means either the cpu or MB has problem. If you don't have other cpu or MB to test, go to local PC shop ask for help.