Logic and display reference section of the power supply

CR1/CR2 (1N5401) rectify the 11.5 V AC and C1 filters it; a 723 regulator with pass transistor Q1 makes +5 V, set by R4 (1K), with R1A (0.18 ohm 2 W) sensing current. The +8 V filament bias comes from 8.2 V zener CR21 (1N4738) and R21; the +4 V comes from two 1N4148s (CR22/CR23) off +5 V. The 8 V and 4 V feed the centre taps of the 5 V and 3 V filament windings.

Systems

• Gottlieb System 1

Related tips

• System 1 power supply outputs
• Replacing power supply filter capacitor C1
• Getting to the power supply solder side
• Power supply bring-up, step 1: inputs
• Power supply output connector pins
• Quick checks on the similar System 1 power supply
• Power supply bring-up, step 2: CPU load
• No +5 V or only 2.4 V from the power supply

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