I've had an Ender 3 for about a year and a half now and have been using it without issues. Last week it turned off a few minutes into a print and wouldn't turn back on on power from the PSU. Connecting a laptop to the usb port does turn on the screen, which makes me think that the board should be fine.
Some investigation revealed that the glass fuse in the PSU power connection was blown. I've replaced that and also ordered a replacement PSU, but the printer still won't turn on. The PSU is outputting 24 V, I've tested that with a multimeter and attached a picture.
I'd be very grateful for any further hints as far as debugging this issue goes. I feel like the next step might be buying a new mainboard and testing with that, but I want to make sure I'm not missing anything obvious.