Question Computer suddenly does not turn on, RAM LEDs are on, paperclip test fails

tones31

Commendable
Mar 13, 2017
4
0
1,510
I have a Seasonic Focus 850w with a ASUS Aorus mobo.
Today it no longer turns on, however, my RAM LEDs are on.
I tried the paperclip test and it seems to fail.
What's really weird is if I hold the case power button long enough, the RAM LEDs turn off. If I press it once, they turn on.
Also when I unplug the PSU for a long time, then plug it back in, a whole bunch of lights on the mobo turn on then off super fast - too fast to see what ones.

Before I go replace my PSU, are there any other test? CMOS battery is fine. How can I be sure it's not also the mobo?