Skee Ball - Ball Counter Display
Link: Full Size Image
Skee Ball alleys feature a single digit display to track the number of balls thrown. A switch at the bottom of the target area is closed by the ball rolling under it and into the ball return track. The signal increments the displayed number. I assume a reset signal is also sent on coin up to set the ball counter to 0.
The board behind the red plexi is a 7 segment light controller featuring a 74LS48 controller. Each lamp socket is managed by a 2N2222 Bipolar Junction Transistor that serves as a switch for each lamp.
Trouble
We had a unit where the top segment stayed lit. This made 1 look like 7 and 4 look like 9. We swapped the 2N2222 with a known working one (top left segment) and observed the same result. Therefore it was not a fault in the 2N2222. On this simple board, the lamps are good, the sockets are good, the transistors are good, must be the chip.
We acquired another 74SL48 and soldered it in place. Now it works perfectly.
Pinout
Pinout Coming Soon.
More Photos: Ball Counter