Some impressions from the cleaning process
State of the playing field Before / After
I used white spirit and spot eraser pads for cleaning and automotive wax for sealing it.
The insides Before / After
The playfield has been stripped and all cables removed. I kept the leaf-switches but will read them in a matrix configuration.
It was possible to take out the relay based control board in one piece. The new ARM based control board is already in place.
In its original configuration, the pinball contains only one single transistor which is part of a delay circuit. All the other functions were done electromechanically.