2 PSU connected to one rig.
1 PSU
to
MOBO
CPU
GPU
Riser
HDD
2 PSU
4 x RISER
4 x GPU
the 2nd PSU with the shorted Power Cable. Fans runs but no power to the riser or the GPU.
1 PSU
to
MOBO
CPU
GPU
Riser
HDD
2 PSU
4 x RISER
4 x GPU
the 2nd PSU with the shorted Power Cable. Fans runs but no power to the riser or the GPU.
I don't know if it will solve it but I recently upgraded to a dual power supply setup which had me researching on how to connect them safely.
I came across posts suggesting powering the riser and PCI-E power connector on the card with the same PSU. Others say the psu that powers the motherboard must also power alll the risers. The slave psu should only power the PCI-E power connector on the card.
https://bitcointalksearch.org/topic/m.17825999
https://bitcointalksearch.org/topic/m.18351224
Ultimately, I did follow the latter suggestion as it seems logical the same power supply that powers the motherboard should also power the risers connected to the PCI-E slots on the motherboard. The second slave power supply only powers the 6 & 8 pin auxiliary power connector on the video cards. According to another post I came across that connecting the PSU's that way ensures they share the same ground, which is important.
https://bitcointalksearch.org/topic/m.4878774
Some cheaper PSU's also use the 5V rail to regulate power, so you could try plugging in a 5V case fan directly to second PSU or test the ATX connector pins with a multimeter.