AY-3-8500 Rifle Game Mod & Circuit

The TV Master MK IV has capability to provide two rifle games, however it requires the addition of a small circuit consisting of two integrated circuits to enable them. Pin 19 is for selecting "Rifle Game 2" and pin 18 is for selecting "Rifle Game 1". After selecting these games, the IC senses the input pins 27 and 28. The signals for these pins come from the rifle, which the circuit below shows.

In Rifle Game 1, a large target bounces randomly across the screen. The object is to aim the photocell in the rifle at the target. Pulling the trigger, increments the shot counter. A hit results in the generation of sound, and the target blanks for a short period. After 15 shots, the score appears, however, the game can continue without additional scoring. In Rifle Game 2, you press the serve button to release the ball, which moves across the screen from left to right. The rest of the game operates exactly as Rifle Game 1. Pin 26 receives the signal from the rifle trigger circuit, known as 'Shot Input', whilst pin 27 receives the signal from the photocell circuit and is known as 'Hit Input'.

Circuit Diagram

Click the image above for a full schematic. My site is the only one that shows how to enable the rifle games for the AY-3-8500. It uses a clever bit of reverse engineering to figure out how it all works.

Circuit Connections

This input connection is for when the Rifle is used.

This Article Continues...