Measuring voltages on a display board

Steps

• Read +60 V DC across the 1 mfd filter cap on the board, or between pins 9 and 10 of the UDN6118 driver.
• Read the 5 V AC filament across tube pins 1 and 37.
• Read the +8 V DC offset from tube pin 1 or 37 to the negative side of the 1 mfd cap or any ground.
• Check a four-digit board the same way.

The display supply runs at 60 to 69 volts; work on it with the game off and never plug or unplug display connectors with power on.

Systems

• Gottlieb System 80
• Gottlieb System 80A

Related tips

• The display voltages to check
• How the Gottlieb fluorescent displays work
• Meter check of the display board 7432
• Checking the +60 V filter caps on a display board
• Replacing a display glass tube
• How the System 80 fluorescent displays light
• Meter check of the UDN6118 display drivers
• Use the shared wiring to locate display faults

Source: Troubleshooting Gottlieb Displays (On Target technical newsletter, vol. 3 issue 7, 1982), Gottlieb "On Target"