Finally built my FD1089/FD1094 programmer so I can test an idea out. Grabbed my box of maybe "dead" FD1094 and used the verify function. Amazingly,8 out of 12 still verify as having valid security sram, held for nearly 40 years.Except for my "good" Golden Axe cpu with a bad byte.

One of the battery wires was corroded where it enters. Fortunately, the resin melts when heated, and I was able to solder it to the nub of remaining wire.Measuring the resistance between + & - shows a high but measurable amount showing it's actually soldered. It holds the key ok.

@Jun0Man What idea you have in mind? 😁