Not really true, Antminer S9  is made to run on 12.xx volt DC , how you power up the power supply does not matter, it can be 110v ac , 220v or even a hamster wheel for that matter.

The issue here is that apw3 can only deliver 1200w when on 110v so he needs to run the miner on lower settings.

However the psu he uses is lianli 2500w which iirc correctly does give a total of 1800w on a 110v circuit which should be enough, more than enough to run an S9 even on old non-asicboost firmware.

However according to the kernel log, hashboard 6 is causing the miner to be unstable,  so to answer the question in OP , yes it is perfectly fine to unplug one of the hashboard ( the once you call chip in op, it is hashboard not a chip).

Simply unplug the 3 6pin cables , you don't even need to remover the data cable, then post your results.