Bob,

I'm glad to read the switch works.

I've observed large amperage switch contacts oxidize and prevent micro current flow first hand. My employer removed a 3/4 hp electric motor but left the 30 amp dual contact power relay to activate a solid state circuit. The circuit kept failing by not activating on command. Technicians would check continuity and the circuit would work for awhile before failing again. Failure analysis finally discovered the relay contacts were oxidizing and preventing the solid state circuit from receiving an activation signal. The problem was resolved by increasing the solid state circuit load enough to prevent the contacts from oxidizing.

Mid seventies Pioneer receivers developed a similar symptom. They used a mechanical relay to energize the over current protection circuit, By design if everything worked right the relay contacts closed and enabled the power amplifier. The relay contacts oxidized which caused the power amplifier to shut down in an over current condition. Run a continuity test, everything checked out and worked again for awhile.

It takes a certain amount of current to clean the contact surfaces when they mate and separate. The minimum current needed is dependent on the composition of the material used to create the contact surface.

Jim Fogle - 2024 BiaB (1111) RB (5) Ultra+ PAK
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