Just sharing my experience and hope to get some valuable comments.
Currently all the risers 103C on 6pin and GPUs are powered by HP Server PSU 1200W; a Corsair 750W PSU power the motherboard and HDD. This has been running flawlessly for over a month. I had earlier power all the risers thru the Corsair PSU using both sata and molex connectors and the HP PSU to power the GPUs. This method also works for me.
However, I have once fried the CPU (ya CPU, not GPU) while all GPUs and risers powered by HP PSU except for 2 risers powered thru the Corsair PSU using sata. I'm not sure if this is not proper perhaps someone could share you thots.
After hearing your incident (TS),I'm not worried I mean I'm getting a bit worried because all my other spare risers are 103C 
Currently all the risers 103C on 6pin and GPUs are powered by HP Server PSU 1200W; a Corsair 750W PSU power the motherboard and HDD. This has been running flawlessly for over a month. I had earlier power all the risers thru the Corsair PSU using both sata and molex connectors and the HP PSU to power the GPUs. This method also works for me.
However, I have once fried the CPU (ya CPU, not GPU) while all GPUs and risers powered by HP PSU except for 2 risers powered thru the Corsair PSU using sata. I'm not sure if this is not proper perhaps someone could share you thots.
After hearing your incident (TS),