There is a 16V8B series PLD (Programmable Logic Device) on the computer board. The PLD's data-sheet indicates that the device is rated for 20 years of data (configuration) retention. As these instruments are now going on 30+ years, this poses a vulnerability. Another blogger and I worked together to determine the necessary logic equations to replicate its function. His power supply was a Motech PPS-1002 and while there are differences his map of the computer board is largely identical to the PPS-2322. As such, these equations ought to work for everything in the PPS series.

The design files used by WinCUPL and the Burn-Ready .jed file are available as files linked to this project. While I tested this using old Lattice Semi GAL16V8B chips, it should also burn to the ATMEL version(s) of the 16V8B available as new stock from the typical electronic parts catalog companies.