It is found that large pole pieces are needed on the low frequency magnets to give good frequency output, but it is necessary to use smaller ones on the high frequencies to prevent excessive iron losses. Small coils are used on the higher frequency magnets and larger coils on the lower frequencies.
Each time a tooth passes this rod it causes a change in the magnetic field which induces a small voltage in the coil, the frequency being determined by the number of teeth and the wheel speed. The tip of the magnet at the coil end is ground to a sharp edge and mounted near the edge of the tone wheel. In addition, “hunting” is suppressed by the resilient couplings and inertia members of the synchronous motor proper.Īssociated with each tone wheel is a magnetized rod about 1/2 inch in diameter and 4 inches in length, with a coil of wire wound near one end. If the tone wheels were rigidly coupled to the motor, this slight irregularity would carry extra frequencies into each tone wheel.
TONE GROUPS ON HAMMOND B3 TONEGENERATOR SERIES
The synchronous motor does not deliver absolutely steady power, but rather operates with a series of pulsations, one with each half cycle. The two spring couplings on the motor shaft, the flexible couplings between sections of the drive shaft, and the tone wheel spring couplings all contribute to absorbing variations in motor speed.
TONE GROUPS ON HAMMOND B3 TONEGENERATOR GENERATOR
If oil of varying grades is used, it is likely that the generator may be sluggish in starting, and in time the threads may gum up and prevent the proper flow of oil. It is very important to use the recommended grade of oil regularly, as it is essential to the proper operation of the organ that the generator be well lubricated.
The drive shaft and both motors are lubricated in a similar manner. Thus, oil from the trough is carried by capillary action to all bearings, penetrating them and lubricating the actual bearing surface. The individual tone wheel shafts are mounted in bearings made of a special porous bronze and each of these bearings is connected to the oiling system by a cotton thread from the oil trough. the number of teeth on each of these tone wheels, in conjunction with the speed at which the tone wheel is revolving, determines the frequency of the tone generated.Įach driving gear, with its two bakelite gears and four tone wheels, runs in a separate compartment magnetically shielded from the rest by steel plates which divide the generator into a series of bins.Īll four tone wheels in any one compartment run at the same speed. Each of the driving gears engages two bakelite gears associated with opposite rotating assemblies.Įach high point on a tone wheel is called a tooth. There are 48 rotating assemblies, each consisting of a shaft and two discs known as tone or phonic wheels. These assemblies are coupled resiliently to the drive shaft. The starting motor is mounted at the end of this drive shaft, opposite the synchronous motor. Twenty-four driving gears, two each of twelve sizes, are mounted on this shaft, and the drive shaft itself is divided into several sections connected by flexible couplings. The main generator consist of the generator proper, a shaded pole induction motor for starting, a non-self-starting synchronous motor for driving the unit after starting, and a vibrato scanner mounted on the run motor for creating the vibrato effect.Ī drive shaft, resiliently coupled to the synchronous running motor, extends the entire length of the generator. Technical Description From Service ManualĮach Hammond Organ Console has a main generator within it, and in some cases, depending on the model, a chorus generator.
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