So I am new here and I just need help with the PC. So I am fixing my friends PC and I get "no signal" on my monitor and black screen every time I start a game or just randomly. The PC still works but I can't do anything. I thought that the GPU was the problem or something so I pulled it out and plugged it in my PC to test it. And it works fine. Then I plugged my GPU in his PC and his PC started working fine too. The problem only happens when I put his GPU in his PC. What could be the problem? His GPU is RX570 STRIX 4GB. Maybe it's the PSU. He has some bad MS 550W PSU and 6 pin molex for his GPU, but still when I plugged in my XFX RX580 8GB card and plugged in that same PSU and molex it worked fine. I appreciate every answer I get. Thanks in advance!