Leftover bits and pieces mostly.
Around 30 years ago, I became the first guy to figure out how to diagnose and repair the electronics in an obscure European brand of pinball machines. This spiraled a hobby in to a side business, and for most evenings in the last 25 years, I did mail order board repairs for customers around the world.
To the right of my bench:
All of the ICs, and passive bits and pieces needed.
The other view:
My home made test bench. Top left board is the CPU. Bottom left is an interface board to drive the solenoids (24) and lamps (80). Top right is the sound board, this one with two audio channels and one speech. Bottom right is the power supply.
Inside the box is a transformer, and some custom hardware I built around a BASIC Stamp to perform automated testing of these boards. A CPU board being tested may be running “game“ ROMs (software) or the custom “test” ROM I designed and wrote in Signetics 2650 assembler to make it easier to diagnose failures.
Behind the box is my ROM burner, an old DataIO that can handle old weird chips like the 2708 as well as the more modern stuff like the 2764.
Lots more info is on my web site
www.zaccaria-pinball.com