Many problems in tube organs are related to oxidized high-voltage pins and sockets, and switch contacts. However, most often a tube has ceased to function. I recommend an annual preventive maintenance plan which includes removing all tubes, then cleaning the glass surfaces, pins, and sockets, and all the switch contacts. Periodic maintenance has been proven to reduce the number of malfunctions in any electronic organ. Leslie speakers , whether built into the organ console or as a stand-alone unit, employ between one and four motors .
Motors require periodic lubrication, and removal of dust from the cooling vents.
Rubber drive belts wear down, developing flat spots. Cloth belts gradually stretch, requiring periodic adjustment, eventually fraying into pieces. When Hammond began to use solid-state active components in their designs, printed circuit boards were designed with contacts etched into the copper foil. They are called PC board edge connectors . An electrical plug could be fitted onto the edge of the board to make connections via the foil contacts without using a separate socket.