The interrupt and reset switches both connect chosen points in the MLB circuitry to ground. If you get part of the expected result of pressing one of them, but not the whole result, it suggests an open circuit somewhere else. It is not beyond possibility that the open circuit is the result of a broken trace on the MLB, caused by the universal villain: leaked capacitor goo. If your SE/30's MLB has not already been reworked to replace its original capacitors, a thorough board wash followed by minute trace inspection and component replacement may be staring you in the face.

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