Depending on the model, about 100 spinning disks create the individual pitches. The waveforms created by the Hammond organ are sinusoidal flute tones. The ability to mix the pitches at varying degrees of amplitude offered a wide array of tonal combinations to the organist. These organs were used extensively during the early Rock'n'Roll era. Many keyboard artists still insist on using Hammond organs today for their distinctive sound. When my children were small, they could even pick out a Hammond organ on the radio! The last tonewheel generator organs were built in the mid-seventies.

They truly never need tuning. Many organ sales people have lied to their customers, stating that the organs they sell never need tuning. I know, because I have to break the news to them when their organ is going out of tune! But Tonewheel Hammonds really do not deviate from the correct frequencies. Pitch is controlled by one synchronous motor operating on the sixty Hertz line frequency of the incoming 120 vac (US - varies by country). All of the spinning disks are mechanically linked to the synchronous motor by gears.

Periodic lubrication is essential to the life of a Hammond tonewheel generator organ. Fresh oil keeps all of the brass bushings and motor bearings from wearing out or seizing. Hammond recommends annual lubrication for most of the Tonewheel models, quarterly for some. Neglecting the annual lubrication is like neglecting your car's oil change. A Hammond will normally operate for about ten to fifteen years without lubrication before showing signs of damage - loud screeching noises from the generator chassis - but then you may have to throw it away. Rebuilding the generators is very costly, usually more than the value of the organ. I have successfully extended the life of screeching organs for several more years using Teflon-based chemicals. I still have some used tonewheel generator units available, too.

Each tablet controls several switch contacts. The contacts gradually oxidize, creating an insulating barrier to the electrical current trying to pass through them. Most technicians clean the contacts, but never lubricate the tablet mechanisms. Evidently they are unaware of just removing all lubrication from the moving parts when they sprayed the contact cleaner (a degreaser, also) on the switch. By adding a few drops of oil to each point of leverage on the metal switch bank, the parts will move more smoothly, reducing fatigue (and the chance of breakage) on the plastic tablets. The Drawbars (now called Tonebars) also require regular cleaning to prevent loss of tones.

The different tones are matrixed to the keys and drawbars in a complex manner, due to the primitive switching methods available then ( no MUX chips, serial data chains, etc.!). Each key has nine horizontal contact wires in a vertical column below it. Nine buss bars extend the length of the keyboard, each one aligned with a particular row of key contacts. Nine drawbars control the attenuation of the pitches applied to the nine buss bars. Separate summing transformers for the upper and lower keyboards (on most models) mix all the signals together. "I said all that to say this".. eventually all of those key contact wires will require cleaning. Hammond incorporated a modification (bussbar shifters) into the later models that helps clean the contacts with movable buss bars. But even that will not compensate for thirty or forty years of dust and oxidation! This is a big job, but it will make the organ sound much better than it has in years. Most people don't notice pitches gradually dropping out from the total ensemble in a spotty manner. But then when all of them are back again, the difference is very noticeable.

Older Tonewheel Hammonds have electron vacuum tubes in them. The life of a tube will be lengthened if dust is not allowed to collect on it's glass surface. Dust acts as an insulator, holding the heat inside the tube. Tube pins and sockets need periodic cleaning, too. 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. Unfortunately, after a few decades, the contact surfaces tarnish more quickly, requiring regular cleaning every year or two for trouble-free operation.