Mr. Pinball Tip:

Residual magnetism is the condition where a relay is energized and then when the current is removed, the relay sticks, appearing to remain energized momentarily. You can verify that residual magnetism is occurring by getting the condition to occur and then turning the machine off. If the relay still sticks after the power is off, then you know that you either have residual magnetism or something mechanically binding. Closing and releasing the relay by hand will tell you if a mechanical problem exists.

Residual magnetism can be countered by applying tape between the relay solenoid coil and the actuator plate. The small space taken up by the tape and the tape's insulating properties is usually just enough to break the magnetic field and allow the relay to function properly.

Residual magnetism can be caused by a relay which is attached to its metal base by a non-brass screw. Check that your problem relay has a brass screw. A steel screw will carry the magnetic field into the metal base and affect the relay is screwy ways.
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