They say a APW3++ is insufficient for a S9 on 110/120 volt.
... it likes to be on chain 6 with a separate PSU. Will not work with one psu even if fist hash board is still on chain 6.
Any ideas?
So why did it work until now, 2 months actually, and as well as 6 others one of which has been now 3 months. What changed that caused just this one to act different?
i personally think that you were right on the brink ... with your power delivery. There is a reason why they say that the PSU cannot run an S9 at 110/120v. It needs minimum 1350W to run (meaning 12.27A at 110V, not even accounting for the loses on the PSU) ... and you might have been running right at the limit in your garage. Even a slight drop in voltage or amperage in your home socket ... you would drop under that 1350W mark. (i.e. your house socket was bleeding voltage/current to other devices etc).
Bitmain PSUs are not the most well made PSUs ... and known to do weird things when current is not in abundance.. its highly possible that it just wasnt able to deliver the power to your S9.