Strange, intermittent behaviour of EVGA Z370 Classified K motherboard

[Hogwild]

Hi:

I used to be an IT tech, and still dabble. But let's assume I have next to zero electronics knowledge.

For quite a while now, I've been troubleshooting an EVGA Z370 Classified K motherboard. The first one, out of the package was DOA (Bravo EVGA!). The replacement was fine for about 2 or 3 years, then a strange thing started happening. It would INTERMITTENTLY not power on. 5VSB light is on. The onboard power light lights up. But no fans, won't power on.

Here are the troubleshooting steps I've tried:

- Swapped out for another (quality) PSU. Both PSUs test good via PSU tester and multimeter. Second PSU is brand new. Different model, made a few years later.
- Tested the power switch/shorted the power switch terminals with a screwdriver.
- Tried different PSU cables.
- Tried different CPU.
- Tried stripdown method. Disconnected everything but power cables.
- Tried removing it from my surge protector and plugging straight into the wall.

** Tried resetting to hardware factory defaults. This WILL make the machine boot every time, but will not prevent it from being required to make the machine boot the next time.

This is driving me nuts. Sometimes the board will boot reliably for months and months. Then suddenly, I wake up one morning and it won't boot. I should add that, as far as I've tested, power is very stable in my home.

The EVGA support I've been working with is baffled.


Anyone have any ideas?