As things progressed further with the SDU hackery and I started actually reading out tapes, the SDU I was using suddenly failed completely. Suspecting power supplies, I went over every pin of both of them again, and was unable to observe any transients that would account for killing SDUs while not killing anything else. This leaves me with only one SDU, the one with the failed nubus interface, and it started exhibiting increasing flakiness each time it was run.
I finally got the SDU payload to the point where it could possibly download data and write it to tape; The network parts had been tested on the physical machine, tape reading had been tested, but tape writing had not. My assumption was that my initial failure to read any tapes was due to the age and condition of the tapes, but I had a nagging feeling it could be my tape drive.
Updates are getting a thin because I'm running out of things to update about; The blog has caught up to real time.
Up until now everything has been going better than expected, which means it's well beyond time for something to blow up in my face. This would of course be the disk drives. As they were mounted lowest in the racks (except for the PDUs) they had the lowest prospects of survival. It was also expected that even if the drives themselves had survived, their non-removable filters would be contaminated with mold and they would destroy the HDAs when spun up. That said, it's best to try and know than forever wonder, so I set about getting the drives out for inspection.
The power supply sled was reassembled for installation in the rack. I made a video of this, but it got shot sideways because I forgot to turn off the rotation lock on my phone and youtube can no longer rotate videos on its own. Eventually I figured out how to rotate it without making a mess. (I am bad at youtube.)
Sorry for the delay in posting. Real Life interfered in my playtime.
Removing the 12V PSU required opening the AC feed box in the power supply sled. This was clean as a whistle inside, since it's a sealed enclosure.
You can clearly see where the protective cover was.
The Lambda has two power supplies, one for 5V and one for 12V. These are on a sled with the processor fans, which can be removed as a single unit for maintenance. Removing the sled was a chore due to the heavy weight of the 5V supply, but I got it out without hurting myself.