Diode test of driver board 74175 chips

Steps

• Game off, preferably with the board out, component side up.
• Red lead on pin 8 (ground, lower left).
• Black lead on pins 2-7 and 10-15: each about 0.6-0.7.
• Pins 1 and 16 read about 0.3-0.4. Other readings suggest a bad chip.

Systems

• Gottlieb System 1

Related tips

• Early driver boards lack isolation diodes
• Testing the 2N6043 coil drivers
• How many coils the driver board can fire
• Which driver transistor fires which coil
• Driver transistors Q1-Q4: relays and spare outputs
• Testing MPS-A13 and MPS-U45 driver transistors
• Spare transistors for System 1 boards
• Meter transistor tests are not conclusive

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