Hammond Organ Technical Information
Manual Chassis Assembly

Brought to you by
Keyboard Exchange International


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.

Hammond B3 World is brought to you buy Keyboard Exchange International. Are you looking to buy a Hammond Organ? You can view our current inventory of Hammond Organs for sale. If you need financing for your Hammond Organ we can help! We buy, sell, trade and restore Hammond Organs and Leslie Speakers. Contact us at b3buyer@aol.com or 407-323-7493