Hello. I wrongly connected 2x CPU 4 pin atx to Dell proprietory 8 pin mobo power socket. After that, only fans are spinning, no display and no response from the pc. Belatedly, I know I should have used 24 to 8 pin adaptor. What damage could that have caused?
A dead motherboard, perhaps. What is the exact model for your PSU and the motherboard? You might need to source a PSU that works with the motherboard in order to verify if you've fried it. I'm leaning on the board being dead altogether, if not, the PSU, if not both.