Excellent information! Thanks! I received the 500A I ordered and parted out what I could (modules, missing trim pieces and hardware, etc) and installed it into the 500B. It recognized all the modules, they passed all their tests and I was able to calibrate the various instruments with no problem. So I think we will definitely use this until something better comes along.
I have located a IDE-CF adapter and 2 GB card. Someone is also bringing me a bag of 32MB EDO modules.
The floppy drive fails the CRC test with a new, blank floppy inserted. Any idea if this is a standard Sony-style PC floppy drive? I have not seen much info on replacing that and obviously the 500A floppy drives are of no use in the 500B.
Before we even powered it up we pulled the hard disk and imaged it to file with dd just so we have a backup of the system as we got it. I also found a driver to read/write the byte swapped FAT filesystem on the hard disk under Linux (OpenGPIB). So I think I can construct the new CF card filesystem from scratch on a Linux host without needing the floppy drive. The system software is something like version 1.x dated 1992; which seems old enough to be the factory firmware. When I switch to the CF card I will use the latest version from Agilent.
Someone kindly wrote some nice mainframe-enabled LabView VISA drivers for the 500B, 500C, 501A, and newer which are available from the LabView 3rd party drivers website.
The Ethernet card in it is twisted pair, thankfully.
I intend to setup a rolling service cart with an analog scope, GPIB-based multimeter, PC (Labview, etc), Wifi bridged ethernet switch, UPS (2000VA), etc.