What exact procedure of maintenance do you do? Did you just use compressed air to clean them up?
How about the temp and fan speed?
If it worked before, I believe this undetectable ASIC chips has poor contact with the heatsink.
If you can disassemble the unit again, I recommend cleaning it up, removing the old thermal paste, and replacing it.
Also, test them one by one because sometimes other hashboard affects the other hashboard to send false signals.
I
havendidn't
touchedtouch the miner
prior to the fault. As I stated in my OP, I shut down power to the miner as I was conducting non-related maintenance at the site.
The miner was literally working perfectly, turned off for 10 minutes or so (
I turned off all power at the site while I
changedadded a breaker in the
maindistribution panel), then when it was turned back on it had 3 dead hashboards. If I had been working on the miner itself, it would make more sense
! and point to something I'd done. Also the miner runs from a 12-way Bitmain PDU, and the other 11 on the PDU continue to work fine (therefore nothing to do with me installing a new breaker)I have since been down to the site and changed control board and PSU, but neither fixed the issue. It just literally went from working perfectly to 3 dead boards after a power recycle. Very strange!
I can only assume some sort of power spike / anomaly from the PSU when power was removed.