WhoDunnit (Bally, 1995) developed an issue where the under the playfield slot machine's leftmost reel started to stutter and eventually completely die about after 10 minutes since power on. From a technical side this is pretty much like any modern slot machine, which probably stems from the fact that Williams was also in slot machine business at the time. The reel is driven with a stepper motor and it has an opto switch to indicate home position. It calculates all the symbol positions by steps from that. Each reel has a dedicated stepper driver board, which again is driven by the game software over a solenoid output. We can easily measure that it's not the drive transistor on the game's main driver board, so it's either wiring, stepper board or the motor itself. I swap the center and left reel's motor output and opto switch connectors around to see if the problem moves to the next motor. It does not, the left one fails with known good board. I power the machine down and feel there's strong resistance in the motor. A touch test (bad idea in hindsight) reveals the motor is extremely hot and the bearings are probably dead now. Final verdict: replace the motor. #pinball #repair