hp probook 450 g2 can not power up , AC light blinking and power button light on. What do I do ?

[tomrehanuncle]

I have a 2013 HP ProBook 450 G2, and one day(randomly), i tried to turn it on, and on the first try, it turned of on its own, then i tried 3 more times and same thing happened, then it booted just fine. Then again, when i was using it, it shuts off on its own, this times when i try to turn it on, the caps and num flashes, telling me i have a bad ram, i replaced the ram, but same thing happened, i test the old ram onto another system and it worked fine. After few more tries of booting it up, it finally turned on and booted as normal, but after that happened, it kept on happening, I would never turn on at first try, (it would boot mostly on 2nd or 3rd try), and after a month, it completely shuts on and no longer powers on even with the good ram, and after another month, the power led blinks when i plug inn power (either from battery or adapter) and the power button stays on and nothing else (it wouldn't even turn of by holding down the power button). I have ran out of ideas, what do I do now ?

[Huffer · Accepted solution]

It has all the signs of a failed motherboard, which is not unusual after 11 years.