CPU-controlled lamps are all out; TP1 reads no DC.

No feature lamp voltage at TP1 (-18 board)

Cause: Tarnished or heat-damaged F1 fuse clips, or a shorted BR1 if F1 is blown.

Checks

• Inspect the F1 clips for browning and weak spring.
• If F1 is blown, test BR1.

Fix

• Replace the F1 clips with tin-plated beryllium copper ("BC") clips; brass clips cannot carry the current.
• Replace BR1 if shorted; this is common.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Related tips

• None of the controlled lamps light
• How Bally controlled lamps are powered and switched
• Dim controlled lamps and a buzzing expander relay
• No general illumination after a new rectifier board, fuses good: check the bulbs
• Finding a short that blows GI fuse F5
• Find a short that blows the 20 A GI fuse
• Controlled lamps dim and TP1 reads about 2.8 V instead of 5.4 V: half the bridge open
• One controlled lamp does not light

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)