is it possible to unplug 2 boards and start with only one board at a time?
that way you could try to find out what each board(PCB) can do?
Don't know if this could help somehow?
Its not advisable to plug powered connectors into yoiur boards , it can give them a spark that could pop something. text book start up is PSU off plug in boards and power up machine then plug in control board.. least i think

that's how the Bitmain site says to do it.. i just personally plug all the connectors in then power up the PSU
Yes that's correct, i work in IT, and that is pretty much standard way to power any IT equipment. Thinking about it, it is pretty much standard to use ANY electrical equipment, but more so in any IT gear as the circuit boards are hypersensitive to voltage spikes/surges.