Well, finally started tearing into them and its been time consuming trying to understand how these work but slowly sorting things out.
So far I have figured out that these e3’s missing chains can be caused by (a) bad hash board or (b) bad processor which is mounted to the hash board among the usual parts such as the signaling cable and controller board.
So, I’m finding some rigs with bad hash boards, bad processors, and some with both so now that I can figure out whats what I have just started cannibalizing parts from the bad rigs and restoring the remaining rigs to 100%. Time consuming AF but going to be nice once get them done. I’ll try posting some pic’s from the process which will probably seem caveman-ish to to someone with electronics skills.