Checking and setting +5 V at the CPU board

Steps

• There are no test points; use connector A1P1 (pin 1 +5 V, pin 4 ground).
• With the game on, read DC volts: 4.95 to 5.15 V is right.
• If outside that range, adjust the trimmer on A2.
• If the reading wanders over time, replace the trimmer.

Systems

• Gottlieb System 3

Related tips

• How the A2 +5 V supply works
• A2 has no overvoltage shutdown
• +5 V wrong or drifting; resets after a few minutes
• Swapping A2 for a switching 5 V supply
• CPU board 26285 versus 26285-1
• Main chips on the CPU board
• CPU board connector uses
• Reading the CPU board LED

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)