Define R4 switches causing a boot failure?

[Lepardi]

One morning this week my 2014 PC suddenly had difficulties to boot up, and then stopped booting altogether. I stripped down the whole thing and reinsterted everything, tested memories fully with memtest (0 errors), before I got the idea to give the power button a firm press and keep it there for a couple of seconds.

This way it boots up every time. I switched power to the reset button on the mobo, but it also requires the same long firm press. Any ideas?

 

[Denpepe]

What happens if you use a screwdriver to start the pc iso the buttons? Should be a quick test to see if it is the chassis or the mobo.

 

[Lepardi]

What happens if you use a screwdriver to start the pc iso the buttons? Should be a quick test to see if it is the chassis or the mobo.

You mean sticking a screwdriver to the power button jumper makes the PC boot?

Fractal had a cheap 5€ power+reset kit in their spare part shop so I ordered that one. I changed the CMOS battery also, so that's one more thing to eliminate from motherboard's side.

 

[Denpepe]

You mean sticking a screwdriver to the power button jumper makes the PC boot?

yeah, the power button does just that, connect that jumper for a moment and start the pc, a lot of peole use the screwdrver trick to test their hardware b4 putting it in the case.

 

[Lepardi]

Switched in the new one, working perfectly even in a cold boot now.

I just don't really get the real cause behind it. How does a worn out power button boot up the PC, but just leave the fans spinning without signal to monitor?