If your power source is 110v the miner will run abnormally because Antminer s9 is made to run at 240v, not in 110v.
The PSU APW2 never heard this PSU before are you talking about APW3 or APW3?
Can you try to "
Test hash board one by one"
If the hashboard running fine in the single hash board it means that the PSU is not giving enough power.
Solution: you need to buy a step-up transformer to be able to run them at full speed.
Correction, their miners are made to run at 230v @50Hz, this is what they will test their PSUs first and foremost, because, that's the mains in China. The other voltages are more or less lab test conditions. Of course most of those PSUs work happily with a bit less (such as 208v from two 120v phases) or 240v as you get in America for dryer/AC circuits at home or such.
But this also means, slight deviations will get into the danger zone faster, such as going 250v peak that in China would have been a 240v peak...
OP should indeed test each single board separately, and swap data and power cables, the usual procedure. And remember to test them for an hour or so hashing.
And yes, S9s are not meant to run at 110v... maybe if you stick to use two boards only (remove the middle one), like the R4 used to.
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.
This is theoretically not allowed by most electric codes, no "110v" circuit (actually 120, some places 115) should go above 1500w ever. You are over stressing the circuit and the PSU. But of course technically the input the hashboards want is 12v and some hundred amps (i forgot).
Perhaps using two PSUs from different phases would be better, but then again if you can do that you can also do the 208v "magic" trick...