Having repaired a couple of Doctor Who (Bally, 1992) machines, I've found that the Time Expander mini playfield always needs to be rebuilt. There are two main parts to this:

1. Rebuilding the mini playfield (and main playfield, if necessary) wood edge;
2. Rebuilding the mini playfield gearbox and cleaning the entire assembly.

This is a small write-up of how I approach these repairs and what the end result looks like.

Up until recently I had been putting up with some strange display issues on my Doctor Who (Bally, 1992) and Judge Dredd (Bally, 1993). Each game worked well enough but there were artifacts on the display that should not normally be present. Since I was about to sell the Doctor Who, I decided to finally figure out the issues with both display driver boards. I also figured it would be a good opportunity to write a general instructional post about integrated circuit replacement on a circuit board.