I have a stack of PCB's (circuit boards) taken from a BAE146 aircraft's engine thrust modulator system LRU (Line Replaceable Unit) which has technology onboard similar to and the same vintage as the Sinclair ZX81.
The other item is a fuel summing unit from a Boeing 737 - that isn't much better in terms of computing tech but these units are interesting to look at and see what components are on them.
Lots of military spec components on here too and some old BCD to 7 segment display drivers meant for driving Panaplex displays; a type of Neon display similar to Nixie tubes. These displays can be seen on the TMS pilot interface unit on BAE146 cockpit photos. They are 3 digits.
Video showing it in operation (MS flight simulator) • MSFS | Tutorial | 146 Professional | Under...
A website sells clocks based on this technology if you want to check it out at https://www.panaplex.co.uk
When this video was recorded I had no idea what these came from so I simply asked the seller where I got them from who told me a lot more information on them. Rather than re-record I updated the video description.
My blog https://www.adrian-smith31.co.uk/blog
00:00 intro
00:45 BAE146 engine thrust modulator unit PCB's
06:48 Boeing 737-300 fuel summing unit main electronics module