No CPU controlled lamp works.

None of the CPU controlled lamps light

Cause: The CPU lamp bridge rectifier (the one nearest the ground strip) or its 5 A slow-blow fuse; also the T relay contact that feeds lamp power.

Checks

• Check the CPU lamp fuse.
• Diode-test the bridge nearest the copper ground strip.
• With the game on, look for 6-8 V DC at the lamp sockets.

Fix

• Replace a bad bridge with a 35 A lug bridge (MB3502/MB3504).

The bottom panel carries 120 volt line power; unplug the game before touching the transformers, line filter or fuse block.

Systems

• Gottlieb System 1

Related tips

• No CPU controlled lamps light
• All CPU controlled lamps are dim
• How the Tilt and Game Over lamps are switched
• Backbox or playfield GI always off
• How CPU-controlled lamps are driven
• Coil, CPU lamp and GI supplies
• Bottom panel fuse keeps blowing
• Testing a CPU lamp circuit by grounding its driver

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