PC desktop having problems turning on

[taith]

CPU: i7 2600

MB: Asus P8P67

PSU: SeaSonic Platinum Series SS-400FL2 Active PFC F3 400W

Case: SilverStone Precision Series PS06B-W Black

Symptoms: after complete shut down of the system computer does not turn on, LED on motherboard is on, indicating there is idle power to motherboard provided.

Because I was lazy my solution so far was: unplug 24PIN from motherboard, wait for LED to turn off, plug in, hit POWER button and hope for the best, if not repeat.

However last time it did not want to turn on after more than 3 tries and it annoyed me.

About myself: I have few multimeters, having decent electric/electronic knowledge and soldering station, good at soldering trough hole stuff, not so much SMD.

Hard to pin point problem, if it is motherboard or case switch or maybe PSU switch.

[tom_w141]

When you have been together for this long turning it on won't be as easy as it once was when passions ran high. More effort will be required.

 

Seriously though you have likely solved it yourself. I'm betting the switch has given up. Turn it off and short the pins on the mobo to act as the switch. Failing that its the mobo but I'm betting switch.

[taith]

Hmm short them on 24PIN connector while plugged on MB? or short it where case button is plugged on MB?

It may take a while to try, as this does not happen all the time and I turn off PC like once a day.

[Syncrosys]

Short the MB where the button is plugged in.

If the same thing happens when you short it, then @tom_w141 is right, its the mobo, but could also be the PSU. Especially if its as old as the PC.

[taith]

Well maybe it's old, but this crap is happening since very beginning.

However this PC did live trough many accidents, like baked ground cable, passing 400V trough PSU as well as old crusty fuses blowing up as well, but before that sparkling so much it made my lights dim (that PSU saved me so many times)

[Syncrosys]

6 hours ago, taith said:

Well maybe it's old, but this crap is happening since very beginning.

However this PC did live trough many accidents, like baked ground cable, passing 400V trough PSU as well as old crusty fuses blowing up as well, but before that sparkling so much it made my lights dim (that PSU saved me so many times)

That's fine. That's why we're troubleshooting. Once we're done you'll know why its doing it. You are starting to make a good case for mobo+psu issues though. They often go hand it hand.

[taith]

Shorting pins on PWR switch did not yels any results, measured resistance on case switch, 0Ω - like new. After shorting pins on PWR I heard caps discharging for a sec, then nothing.

Then clumsily tried to short PWR on 24PIN connector, not sure if I did it or not, but thing did not turn on.

Then I unplugged 24PIN and shorted that way (rest of cables still plugged on board) did not turn on. Voltage of PWR ON to ground 3.3V.

What I LOVE is repeatability, I did tried trough few days shorting unplugged PWR ON after failed turning on. in about 25% of the time it DID turn on...

So case out, yet power supply and motherboard keeps confusing the crap out of me.