Datasheet for the SN7427N, a triple 3-input positive NOR gate in plastic DIP, supplied as a 13.3 KB PDF. It lists the pin assignments for each gate, the truth table and electrical ratings for the standard TTL version. To test the chip, confirm that each output is high only when all three of its inputs are low, using a logic probe or scope. Before ordering a replacement, check the exact part marking and family suffix on the package.
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