Some playfield switches never register.

One or more playfield switches do nothing

Cause: Switch adjustment, an open isolation diode on the playfield terminal strips, a broken cable between playfield and control board, or a strobe or return line shorted to ground.

Checks

• Adjust the switch.
• Test its isolation diode on the playfield terminal strip.
• Check the cabling between the playfield and the control board.
• Look for a strobe or return line shorted to ground.

Fix

• Repair the switch, diode or wiring; otherwise repair the control board.

Systems

• Gottlieb System 80
• Gottlieb System 80A

Related tips

• How the switch matrix is scanned
• The slam input has priority over every other switch
• Where to see the switch matrix strobes
• The play-test button will not start the test sequence
• Switch test (step 18) shows switches closed
• How the 32 option switches are read
• Switch matrix connectors A1-J5 and A1-J6
• One or more controlled lamps never light or stay on

Source: System 80 Service Manual, Gottlieb