I love watching youtube vids of BigCliveDotCom as he is a self employed electric engineer by trade and this vide was one of his that showed an old self build simple by todays standards fruit machine.
Just thought id share it with you.
https://www.youtube.com/watch?v=Q4aQiIXASuI&t=0s
If you have time, try and watch some more vids from him i find them very amusing! lol.