If the special solenoid section of your driver board has gone supercritical, you can save the board and use it in a shuffle alley since they don’t use that part of the board. Likewise if you need a board with a nice special solenoid section you can swap one out of a shuffle alley.

If you don’t know what the special solenoid section is, it’s a cluster of 6 transistors near the flipper enable relay that’s typically used to drive the pop bumpers, sling shots as well as any other needed coils.

The special solenoid section was originally used in early solid state games because it was believed that if the computer had to read the switch then fire the coils the pop bumpers and slingshots wouldn’t be as fast and responsive.

Games such as High Speed have 2 switches on the pops and slings. One fires the coil directly through through the special solenoid section and a secondary switch to tell the game it was fired and to award appropriate points.

It would seem these concerns are unfounded as early Bally games never used this design and fired all coils through the game programming.