Spare transistors and SCRs worth stocking
High-voltage section of the driver board: 2N3584 at Q21 and 2N3440 at Q22/Q23. MPU reset section: 2N3904 (NTE123AP) and 2N4403 (MPS-3702, NTE159). Lamp driver feature lamp SCRs: 2N5060 (NTE5400, 0.8 A 30 V; 2N5062 also works) or MCR106-1 (NTE5411, also called T106, 4 A 30 V). Display driver: 2N5401 (NTE288) and MPS-A42 (NTE287). Coil drivers: SE9302 (NTE263), or TIP102.
Systems
Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)