System 7 board with older firmware shows "u" on the SW1 test

When a System 7 CPU runs System 3 to 6 code, the seven-segment display does not give the System 7 codes. A pass shows as a "u" in the upper segments flashing twice. For real codes, refit System 7 EPROMs, or fit the two test LEDs.

Systems

• Williams System 7

Related tips

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Source: Repairing Williams System 3 to System 7 Pinball 1977 to 1984, Part Two, Clay Harrell (pinrepair.com)