Something really strange just happened to my pc and I dont know if it was down to my PSU or GPU. My pc was powered down and my GPU (ASUS GTX 970 STRIX) LED remained on as it usually does. But the whilst the pc was off I heard a pop and my GPU LED turned off for a few seconds then turned back on. My pc seems to be working fine but I just want to see if anyone has any idea why that happened. My psu is an XFX XTR 550w.