The six Rockwell "spider" chips on the CPU board

U1 11660-CF is the main processor and U2 10696-EE the second; U3 (also 10696-EE) handles some lamps and switches; U4 A1753 drives the solenoids; U5 A1752 reads the switch matrix; U6 10788-PA runs the displays. U4 and U5 hold the operating system in internal ROM. None are made any more.

Systems

• Gottlieb System 1

Related tips

• Swapped U4 or U5 spider still does not work
• Socketing a replacement spider chip
• Spare chips for System 1 boards
• Aftermarket System 1 CPU boards
• Check the TC3 jumper plug on the CPU board
• Powering a System 1 CPU board on the bench
• Checking the U4 solenoid spider with a coin tune
• Ni-Wumpf board coil buffer chips

Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)