Mr. Pinball Tip:
The Williams System 7 CPU board displays values on a seven segment display corresponding to which part of the CPU board failed the diagnostic. The values are listed below:
0 - Test Passed
1 - IC13 RAM faulty
2 - IC16 RAM faulty
3 - IC17 ROM 2 faulty
4 - IC17 ROM 2 faulty
5 - IC20 ROM 1 faulty
6 - IC14 Game ROM 1 faulty
7 - IC26 Game ROM 0 faulty
8 - IC19 CMOS RAM or Memory protect circuit faulty
9 - Coin-door closed, Memory protect faulty, or IC19 CMOS RAM faulty.
These values give you a head start on debugging CPU problems.
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