Use #67 flasher bulbs, not #89
System 3 flasher circuits are built around the #67 (13.5 V, 4 cp, 0.59 A, about 5,000 hour life). A #89 (13 V, 6 cp, 0.58 A) lasts only about 750 hours and on some games does not work at all, so fit #67s.
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Source: Repairing Gottlieb System 3 Electronic Pinball Games from 1989 to 1996, Clay Harrell (pinrepair.com)