Nishijin Circuit Racer

By chance, I picked up a rare Nishijin Circuit Racer pachinko machine. It's one of the few models of that era that utilizes an electromechanical feature. Most pachinko machines from that era are purely mechanical devices except for a couple of lights and leaf switches.

When I first got the machine it was dirty, the back was falling off and the tire feature coil was continuously energized with no power going to the lamps. The cleaning and falling back were an easy fix not worth documenting. The stepper unit required partial dismantling to access the wiper and disc for cleaning.

The feature unit is very nice with a sealed relay, a tiny wiper and disc, a step up coil, a reset coil and a delay circuit for the reset coil. The board also has 4 diodes as a bridge rectifier.

Here's how the unit works.

Under normal conditions, when the feature is not engaged. The stepper unit wiper is in zero position and the sealed relay is energized breaking the circuit to the tire solenoid.

When a ball triggers the feature micro switch it momentarily energizes the step up coil, shifting the wiper one position. The small sealed relay drops out and it's switch makes the circuit for the tire solenoid.

Additional balls in the feature steps up the unit via the micro switch until it reaches last step.

The stepper unit reset coil is energized by the last step on the stepper unit or by the left or right pit stop micro switches. 

Wiper winds back to zero position, small relay is energized by zero position and tire feature solenoid drops out.

Stepper disc steps:

0 - Energizes sealed relay

1 - S light

2 - 2 light

3 - 3 light

4 - 4 light

5 - G light

6 - Energizes stepper reset coil 

Enjoy some reference pictures of the stepper unit. Details are few for this game!