Which spider chips fail and why

U4 (solenoids) and U5 (switch matrix) fail most: U4 is killed by locked-on coils after a driver transistor shorts, and U5 by coil voltage reaching the switch matrix. U1, U2, U3 and U6 seldom fail. Since no spiders are made, a board with a dead spider needs a donor chip or an aftermarket replacement CPU board.

Systems

• Gottlieb System 1

Related tips

• Socketing a replacement spider chip
• Spare chips for System 1 boards
• Checking the U4 solenoid spider with a coin tune
• Ni-Wumpf board coil buffer chips
• Check the TC3 jumper plug on the CPU board
• Odd high scores usually mean a bad 5101 RAM
• Aftermarket System 1 CPU boards
• Dead CPU board: first checks

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