Help. My Ender 3 Pro with Creality V4.2.2 motherboard has died. LCD screen blank (black) and alarm pusing a continous bleep. This happened after a cable connection at the mains plug came loose and gave intermitant power connection, (crackling!). have loaded the Ender-3 Pro_4.2.2_Firmware_Marlin2.0.1 - V1.0.1.bin into a clean micro sd, but no change. Have accessed the motherboard and nothing looks disconnected or fried. Have attempted to search internet for an answer and found it totally confused. I was given this printer last year for my 80th birthday last year, so technically it is probably still under guarantee but would be a very difficult item to return. I have, however, purchased an identical motherboard, not yet received. But worry that it won't help if something else is wrong.
Any help, preferably via simple detailed instructions, would be very welcome. My level of knowledge is limited.