Clamp diode mod to protect U5

An experimental mod adds clamp diodes to hold strobe and return lines at or below +5 V. Across R65-R72, fit a diode with its band at the +5 V end. On R57-R62, connect the non-banded end at the resistor-to-IC junction and the band to a +5 V point.

Systems

• Gottlieb System 1

Related tips

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• Replacing the CPU battery with a remote AA pack
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Source: Gottlieb System 1 Pinball Repair from 1977 to 1980, Clay Harrell (pinrepair.com)