Firing Q1-Q4 from the Z1 latch

Steps

• With the game on, clip a lead to +5 V at the top lead of driver board C1.
• Touch Z1 pins 2, 7, 10 and 15 in turn; each should make Q1 (Q relay), Q2 (T relay), Q3 or Q4 operate its load.
• Make sure the load is not already locked on first.

This check is done with the game on; keep the clip lead away from other parts and touch only the named point.

Systems

• Gottlieb System 1

Related tips

• Spare transistors for System 1 boards
• How many coils the driver board can fire
• Which driver transistor fires which coil
• Driver transistors Q1-Q4: relays and spare outputs
• Meter transistor tests are not conclusive
• Testing MPS-A13 and MPS-U45 driver transistors
• Testing the 2N6043 coil drivers
• Testing the Q45 2N3055 and its resistor

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