If your Bally early solid state MPU LED glows steadily dim and the game
doesn't start chances are that you're not getting 11.9VDC to the MPU. The
LED is driven directly by the 11.9VDC so it should be bright. The problem
is likely a bad connection, a bad bridge rectifier (BR2 on board A2), or a
bad capacitor (C23 11.7K uF on A3). The capacitor, C23, is the largest one
on the solenoid driver board.