Hammond Organ Service Manual - Early Models (A,B ... - Audiofanzine

TONE GENERATOR
The main tone generator furnishes 82 or 91 different musical frequencies,
depending on the console modeL It includes a tone wheels magnet, and coil
for each frequency. Mounted on top of the generator are tuned filters to
insure purity of the tones,
PREAMPLIFIER
The preamplifier is located in the console. Several types have been used
in the various console models. Some obtain their plate voltage from the
power amplifier through the console -to - cabinet cable, while others have a
self-contained power supply,
TONE CABINETS
Tone cabinets are made in a number of models differing in size, finishj and
power output. The numbt-rs 20 and 40 in the model designations indicate the
nominal pow^t'r output in watts. Each tone cabinet includes one or two power
aniplifier^ and two or more speakers.
Cables of special design are used to connect the console to the tone cabinet
or cabinets,
REVERBERATION CONTROL
Tone cabinets having the letter R within the model designation are equipped
with the Hammond Reverberation Control. This is an electro -rnechanical
device designed to supply reverberation for installations that are accoustically
"dead" or have insufficient natural reverberation. A portion of the
musical signal is delayed by passing through fluid-damped coil springs and
then combined with the direct signal. By adjustment of the amount of
delayed signal the reverberation characteristics of large or small enclosures
may be simulated. A tone cabinet having this unit must be handled in accordance
with directions on the instruction card in order to avoid damaging the
unit or spilling the fluid.
ROTOR TREMULANT
Tone cabinets having the letter X in their model designation contain a drum
rotor inount*^d above the speakers and driven by a small motor. Rotating in
the path of sound from the loud speal^ers, it produces the effect of a periodic
voluzne and pitch variation in all tones of the organ.
A switch for controlling its operation can be mounted on the tone cabinet, or
an additional cable w^ith a switch located at the console may be used.
When a console having the Hammond Vibrato is connected to this type cabinet;
use of the rotor tremulant is not recommended.
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