Coils, mostly low-resistance high-power ones such as the vertical up kicker, hold on or leak current intermittently.

Cue Ball Wizard: coils holding on weakly (BUZ72L MosFETs)

Cause: Some Cue Ball Wizards left the factory with BUZ72L MosFETs in place of 12N10L.

Checks

• Read the markings on the driver MosFETs.

Fix

• Replace every BUZ72L with a 12N10L or IRL530 class part.

Systems

• Gottlieb System 3

Games

• Cue Ball Wizard

Related tips

• Spare MosFETs for the driver boards
• What the A3 driver board drives
• Logic-level MOSFET equivalents: 12N10L, 20N10L, 22NE10L, IRL530, IRL540
• Coil or flasher on as soon as the game powers up
• Testing a dead coil or flasher
• Coil MosFET ratings and substitutes
• Diode-testing the 12N10L/IRL530 MosFETs
• Only logic-level (L) MosFETs work on the driver board

Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)