The pop bumper's 2 A slow-blow fuse blows each time a game is started, though the coil reads 2.5 ohms or more and its 1N4004 diode is new.
Pop bumper fuse blows every time a game starts
Cause: An internal short in the 74LS121 or 74LS16 on the PBDB.
Checks
- Meter on diode test: hold the black probe on the chip's +5 V pin and touch the red probe to every other pin; all but the ground pin should read 0.4 to 0.6.
Fix
- Replace the failing chip.
Systems
Related tips
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Source: Repairing & Upgrading Gottlieb System 80 Pinballs from 1980 to 1989, Part One, Clay Harrell (pinrepair.com)