Question GPU power supply not turning off when main power supply turns off.

[jstateson]

I have several open rack systems running BOINC. On one of them I replaced a small 750 watt with a larger 1200 watt that was more efficient. It handles 3 GPUs. I used only the 12v PCIe cables. Both to the GPUs and to the risers the GPUs are in. None of the peripheral cables (5 & 12 SATA) were used. Unlike the 750 watt power supply, the 1200 watt does not turn off when system is shut down.. Instead, it somehow manages to power the 12v fans that are on the motherboard in addition to keeping the 3 GPUs running. The main power supply does turn off. Flipping the power switch on the main power supply still leaves the second (1200 watt) on. There must be some feedback in the 12v and/or some defect in the 1200 watts that causes the 12v of the secondary power supply to keep the bridge relay from shutting it down. Nothing has been damaged and I put the 750 watt back in. Possibly I can replace the 12v relay in the bridge with one that runs off of 5 volts. Any other ideas?

 

[Ralston18]

Make and model PSUs - the old 750 watt and the new 1200 watt?

Noted that you used only the 12 volt cables. But did you use only the 12 volt cables that came with each of the respective PSUs?

No mixing of cables at all.

Make and model GPUs? Three GPUs in the subject open rack - correct?

Do you have a sketch or other means to explictly show how PSUs, GPUs, etc. are are connected within the rack?

If so, post here via imgur (www.imgur.com).