Segments do not light at power-on and come on slowly as the display warms, or the ones and tens digits look burned even with the game off.

Display glass dim, digits missing or slow to light

Cause: The glass is outgassed: years of high voltage have contaminated the gas. The ones and tens digits wear first because they are lit most of the time.

Checks

• Move the display to another player position; if it fails there too, the glass is the likely problem.

Fix

• Replace the display glass; it cannot be repaired.

Systems

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

Related tips

• Score displays dim
• One segment never lights on a display
• One digit missing on a score display
• One segment always lit on a display
• Classic Stern display: blotchy, faint digits on one display: outgassed glass
• Same digit missing or stuck on every display
• All 7-digit displays show a dim first digit and comma
• Replace a score display glass

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