See the accompanying Hackaday writeup about this schematic project:
https://hackaday.com/2024/11/25/apollo-era-pcb-reverse-engineering-to-kicad
This repo documents additional explorations into the reverse engineering effort of an Apollo-era printed circuit board assemly that Skyhawkson obtained earlier this year. See his project at the original repo.
Note: I planned to submit this as a pull request to Skyhawkson's repository. But I ran into trouble with git and spaces in filenames, a problem I haven't seen before.
This is an interface board for reading sensors such as strain gauges. It features a precision voltage source to excite the bridge. It also has a differential amplifier to scale up the sensor voltage and proportionally drive an output load. The output stage has an enable pin, suggesting that multiple card outputs may be multiplexed into one analog to digital circuit card. That makes sense, since scanning through a bunch of sensors over and over again makes sense in the context of running through test sequences.
If there are any updates based on comments from Hackaday readers or anyone here in GitHub, or just random new insights, I will update the repository as necessary.
Schematic (PDF)
Reverse Engineering an Apollo-Era Circuit Card
https://github.com/Skyhawkson/Apollo-Era-Card-RevEng/tree/main
