Problem

Game would not retain settings after exiting test mode.

Diagnosis

One might suspect that game settings are stored in RAM backed up by the CR2032 battery and super capacitor on the PCB and that the RAM is faulty. However, there is a 93C45 serial EEPROM underneath the I/O PCB which holds the settings:

The EEPROM is interfaced through a 315-5296 I/O expander:

There was activity on the Chip Select (CS), Data In (DI) and Serial Clock (SK) lines when exiting service mode. However, nothing at all was present on Data Out (DO) when entering or exiting service mode. I replaced the chip with a new 93C46 and confirmed that the game would now hold its settings.

Fix

Replace 93C45 at IC76.

Philip Bennett