Welcome to the SeeMeCNC Community

I had a problem with my printer a while ago (October?), where it would lose control and crash the extruder into the bed at an odd angle. I did a couple of emergency shutdowns and left it to troubleshoot later, which turned out to be recently. I found that it would now not even power up. I traced that to a bad power supply. I bought and installed the Power Supply upgrade kit. That is working normally, lights and fan runs etc. But still cannot get the display to light up. I checked all of the fuses on the board and they are good. Can anybody offer me advice on where to look next? I'm not sure if all this is related to the extruder crashing or just a coincidence....

Are you still on the old rambo board? If so... you could have a bad board. I've had two of them go out over the years. I switched to the Duet WiFi and never looked back. Maybe you could send the board into Seemecnc and they could tell you for certain.