Test the CA3081 pre-driver array

Steps

• Switch off and remove the solenoid driver board.
• On diode test, put the black probe on the GND test point just left of U1.
• Red probe on the CA3081 pin that goes to the CR diode: about 0.1 to 0.2 V. Red on the other noted pin: about 0.7 to 0.8 V.
• Reversed (red on GND): the diode pin still reads 0.1 to 0.2 V and the other pin 1.1 to 1.3 V; this direction is less conclusive.
• Other readings mean the CA3081 (NTE916) should be replaced (page 21).

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35

Related tips

• Kickout coil burns up in attract mode: driver transistor, resistor and the CA3081 at U3
• Solenoid driver transistor types
• Test solenoid driver transistors with the game off
• AS-2518-16 and AS-2518-22 solenoid driver boards interchange
• Fire a coil by grounding its driver transistor tab (game on)
• Solenoid driver board: transistor, diode, resistor and connector for each driver
• The CA3081 on the driver board is a transistor array
• Solenoid driver board J3 pin functions

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part Three, Clay Harrell (pinrepair.com)