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Keyboard Exchange International 6914 Hanging Moss Road - Orlando, FL 32807 Sales Office: (407) 671-0730 FAX: (407) 671-2272 We Buy Hammond Organs: Dead or Alive Most Wanted Models: B-3, C-3, A-105, D-152,A-100, RT-3, B-2, BV, BC Contact Us: B3buyer@aol.com Technical Information for Hammond Tone Wheel Organ Page 2
5-23. A vibrato chorus effect, similar to the effect of 2 or 3 slightly out-of-tune frequencies mixed together, is obtained when the vibrato output signal is mixed with a portion of signal without vibrato. For vibrato chorus, part of the incoming signal appears across the vibrato line and the rest across a resistor in series with the line. As the vibrato effect is applied to the part of the signal appearing across the line, but not to the part appearing across the resistor, the combination produces a chorus effect. For normal vibrato this resistor is short-circuited. In the Model C-3 console the vibrato effect can be applied to either manual separately or to both at once. 5-24. Figure 5-5 shows the vibrato line box. Each of the inductance coils is connected with one or more capacitors to form one filter section. 5-25. Figure 5-7 shows the construction of the vibrato switch. S-26. The scanner, shown in figure 5-6, is mounted on the main generator synchronous motor and driven at 412 revolutions per minute. It is a multi-pole variable capacitor with 16 sets of stationary plates and a rotor whose plates mesh with the stationary ones. In figure 5-7, Index B, two sets of plates have been removed to show the rotor. 5-27. Signals coming from the line through the vibrato switch appear on the stationary plates and are picked up, one at a time, by the rotor. Connection to the rotor is made by carbon brushes as shown in figure 5-6, Index A. Two brushes' touch the sides of the contact pin and a third presses on the end, in order to eliminate the possibility of contact failure. 5-28. Figure 5-8 shows the vibrato circuit. 5-29. The vibrato switch has no "OFF" position and 3 vibrato chorus positions (Cl, C2, and 'C3) are included in it as well as the 3 vibrato positions (Vl , V2, and V3). The vibrato effect is turned "ON" and "OFF" for each manual separately by means of "VIBRATO SWELL" and "VIBRATO GREAT" tablets on the manual assembly. 5-30. The preamplifier used with this circuit has two separate channels into which signals from the "VIBRATO GREAT" and "VIBRATO SWELL" tablets are fed. (Reference paragraph 5-37.) The "VIBRATO" signal goes through a preliminary amplifier, through the vibrato system, and then into additional stages of amplification. The "NO VIBRATO" signal also has a preliminary amplifier, but bypasses the vibrato system and goes directly into the additional amplifier stages. 5-3 1. MANUAL CHASSIS ASSEMBLY. 5-32. The 9 contact springs on each key are connected by resistance wires to the proper terminals on the terminal strip and carry the harmonics of the particular note with which they are associated. (Reference paragraph l-20.) The resistance wires avoid overloading of the generators and thus allow each generator to be used independently to feed a number of key circuits. All key contacts are alive at all times. When a playing key is depressed, its 9 frequencies are impressed on the 9 bus bars of the manual. No wires are connected to these bus bars; a preset or adjust key must be depressed to complete the circuit. (See figure 3-3.) Each preset or adjust key is provided with 9 contacts identical to those on the playing keys and is further provided with a locking and tripping mechanism, the purpose of which is to permit only 1 preset or adjust key to be in operation at a time. (See figure l-6.) The cancel key releases a depressed preset or adjust key; this cancel key has no contacts. 5-33. Flexible wires connect the 9 contacts of each adjust key (A# and B) to the 9 drawbars controlled by the key. The wires are color-coded for identification. Each drawbar makes contact (according to the stop position to which it is drawn) with any one of 9 bus bars connected to taps on the mixing transformer. (See figure 3-3.) The bus bars correspond to different intensities of sound. 5-34. The 9 preset keys (C# to A) are connected by flexible leads to the preset panel in the back of the console. (See figure 1-4.) The preset panel consists of 2 sets of 9 bus bars which correspond to those in the drawbar assembly and which are connected to the same taps on the mixing trans-formers. 5-35. The mixing transformers are mounted on the manual chassis assembly as shown in figure 14. Shielded leads carry the signals from the secondaries of these transformers to the pre-amplifier. 5-36. PEDAL SWITCH ASSEMBLY. The pedal switch assembly is similar in operation to the manual chassis assembly (reference paragraphs 5-31 to 5-35 inclusive); the pedal switch assembly, however, contains only 4 bus bars instead of 9. A flat spring at the end of each pedal of the detachable pedal clavier depresses a small plunger, as shown in figure 3-2, on the pedal switch assembly and actuates a double set of contact springs, thus making eight contacts available for each note The pedal contact springs are connected by decoupling resistance wires to terminals. A cable connects these terminals through a wiring tube to the proper terminals on the main tone generator strip. The pedal switch bus bars are connected, by means of four colored wires, through a filter reactor and resistor network to the pedal drawbars. (See figure 5-9.) The reactor and resistors filter out undesirable higher harmonics and serve to balance the pedal tones. 5-37. VOLUME CONTROL AND PRE-AMPLIFIER ASSEMBLY. 5-38. Typical Circuit Before Pre-amplifier. 5-39. Each voltage of predetermined frequency produced by the tone generator is connected to one or more key contacts. When the associated playing key is depressed, this voltage is impressed upon the bus bar and is carried through the pre-set key switch to the preset panel. The voltage is then fed to one of the several taps of the mixing transformer which is associated with the manual being played. From the high impedance secondary of the mixing transformer, this voltage (combined with others which may be fed through simultaneously) passes to one of the preamplifier input circuits. (Vibrato "ON" or "OFF" circuit). 540. Power to operate the preamplifier and power amplifier is supplied through the run switch circuit as shown in figure 3-3. 54 1. Preamplifier Circuit, Input. 5-42. The signal from each mixing transformer is sent to the Vibrato "ON-OFF" tablet associated with its particular manual, and is then carried to the "VIBRATO" or "NO VIBRATO" preamplifier input, depending on the position of the tablet. 5-43. The input circuits are similar, with one extra stage of amplification in the "VIBRATO" channel to compensate for the loss that occurs through the phase shift network and associated scanner. The input tube V4 receives the signals from "VIBRATO" and "NO VIBRATO" circuits and further amplifies them. The signal then is impressed on the "LOUD" stator of the volume control, and on the "SOFT" stator through a compensating network. 5-44. Volume or Swell Control. 5-45. The volume control is activated by the swell pedal connected by an appropriate linkage. (See figure l-4.) The volume control assembly consists of two sets of stator plates, similar to those used in the scanner assembly. (See figure 5-6.) A rotor assembly of similar size is moved by the swell pedal and is capable of meshing with either stator or a portion of each. The degree of mesh determines the strength of the entire signal. 5-46. The signal is further amplified by the second section of V4 and sent to driver tube V3 which in turn drives the 12BH7 output tube. 5-47. PERCUSSION SYSTEM. (See figure 3-3.) 5-48. The "Touch Response" percussion feature is controlled by four tilting tablets (figure l-l ). It is avaiIable only on the upper manual and only when the "B" adjust key is depressed. Percussion tones are produced by borrowing the second or third harmonic (depending on position of the "Percussion Harmonic Selector" tablet) from the corresponding drawbar of the upper manual "B" adjust key group, amplifying it, returning part of it to the same drawbar, and conducting the balance through push-pull control tubes which, when keyed, cause the signal to fade away at a pre-determined rate. 5-49. With the percussion tablet on, "B" adjust key pressed, and an upper manual playing key pressed, the second or third harmonic signal goes to percussion input terminal H on the pre-amplifier chassis and is amplified by T4 and T5. The percussion input transformer TS not only provides push-pull signal for the control tube V7 but also has a third winding which feeds signal back to the 2nd or 3rd harmonic drawbar through equivalent key circuit resistor R50 and terminal "J". |
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