It's the all in one board.

I spoke with Pascal about it and he suspects the original knocker coil was defective so it damaged the driver transistor Q1.

He said to turn the game off and disconnect A3J2 & A3J4 to test the transistor.

My problem is when I have googled how to test transistors whilst they are still on the board I seem to find numerous different ways of how to do it, many of the tests dependent on the type of transistor. The transistor in question is a BDW93C, but I cannot see this relating to any of the commonly referred to pinball transistors in any repair guides etc, so I don't really know how to test that particular type of transistor.  It also doesn't help that I know "F" about this $hit!

Pascal also said to check the diode just below the transistor too.

Fortunately there is a spare diode and transistor that came with the board, but I don't want to unnecessarily replace stuff on the board if its not needed, particularly when my soldering work won't be anywhere near as neat as the original.