Add two test LEDs to a System 7 CPU board

Steps

• Solder two 100 ohm 1/4 watt resistors into the pads just left of test point TP9.
• Solder two LEDs into the upper two of the four pad pairs beside the seven-segment display, flat side toward the display.
• The LEDs then flash like the two LEDs on a System 3-6 board, even if IC34 or the display has failed.

Systems

• Williams System 7

Related tips

• System 7 CPU LEDs are swapped versus System 6
• Identifying a System 3 to 7 CPU board
• System 7 CPU board test points
• A System 7 CPU board can run any System 3 to 7 game
• Run a System 6/7 CPU board on +5 V only
• Late System 7 CPU boards lack LEDs and DIP switches
• Is it the CPU board or the driver board? Boot the CPU alone
• Which CPU boards can run which system firmware

Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)