Adding the Extra Driver Transistor

The auxiliary driver board, under the playfield near the left lower flipper mechanism, uses only five of its eight slots. However, the transistor that we need will most likely not be in your machine, so we are going to have to add it. We also have to add the wiring for the third magnet coil.

Let's start with the magnet wiring. Here's a picture of the rear of the upper right quadrant of the playfield, which is the lower right quadrant when the playfield is up and viewed from behind, like here. And here's where the magnet will go. Note the three dimples at the lower end of the open space in the picture. We'll be back here later, with some tools...
The magnet cable harness is a 2-pin connector with two long 18GA black wires attached. Start by holding the connector and wiring alongside the wiring for the existing magnet. I tucked mine through the existing wire tie.
Run the wiring up the harness; our goal is the driver board, up in the top left of the machine. Add cable ties next to the factory ties, and try to keep the wires in roughly the same position as they run up the harness. We don't want this to look like some kind of climbing weed. Here I messed up. the black wires should go under the flipper wires. I'll fix that when I rewire the flippers.
You can see the route by following the unclipped cable ties. When you have the wires run, disconnect the driver board, remove it, and add the transistor and other parts. See below for adding the transistor.
That was quick! Here's the board with the new transistor added. You can see the new wires hanging over the board. Finish up by pushing the new wires into the open sockets at each end of the connector (+50V and SOL2). This is best done with the playfield in the lower service position (brackets resting on the front of the cabinet). If you look carefully, you'll see that I messed up on SOL2. My wire is not all the way in. I have  fixed this.
 

DON'T TRY TO LOWER THE PLAYFIELD!!!

Here's the new magnet, connected and in a good location for test. Go into solenoid test, and test Solenoid 22 ("Not Used"). It will buzz as the test routines fire it.

DON'T TRY TO LOWER THE PLAYFIELD!!!
 

Adding the Extra Transistor

  
Here's the board, after a bath, on the bench. We are going to add Q3, D3 and R3.

First, we have to empty the holes of solder. To do this, we need  solder ucker and a soldering iron. We could also use braid, but I prefer the sucker.
Cock the solder sucker, then apply the iron to the hole that you wish to clean. Put the sucker over the hole and the iron. Then, release the plunger. The solder will be sucked out of the hole.
It is effective on larger holes. The smaller resistor holes might take two tries. I clean out the heatsink holes, even though we will probably not use them. Here's the board with the holes cleaned out.
Here are the parts that we will add. You can see the transistor, thermal pad and heatsink on the left, and then the diode and the resistor. The screw and nut fasten the transistor to the heatsink with the pad between them. . Here's the transistor assembled.
Put all the parts into the holes. Make sure that the band on the diode is at the left hand end, as shown on the board. You can put the resistor in as you like. Bend the leads outward at an angle while holding the parts cloes  to the board. This will make your life much easier.
Now you can solder the parts. Finally, clip the leads close to the board and clean the flux off with a bit of naptha. Re-install the board in the machine. This part is done.