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

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CI4ART SHOWING SIZE OF TONE OPENING REQUIRED
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FOR REVERBERATION TIME OF ONE SECOND
FOR CHAMBERS WITH DIMENSIONS IN RATIO OF Z : 3 : 4.5
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VOEUlvlE OF CHAMBER IN CUBIC FEET
FIGURE 1.
CONSTRUCTION AND FINISH
All boundaries of a reverberation chamber should be of exceptionally rigid construction.
Concrete or heavy tile is ideal. If the chamber is to be of frame construction
the studs should not be over fourteen inches on centers. Lath should be very securely
nailed and the plaster should be hard and given a smooth finish coat.
TONE OPENINGS
The reverberation time of an organ chamber is greatly influenced by the size of the
tone opening. For a chamber of given dimensions, the reverberation time is increased
as the area of the tone opening is reduced, A large chamber, therefore, may have a
large tone opening and still furnish sufficient reverberation, whereas a small chamber
might require a very small opening. A chart is shown in Figure 1, giving the area of
tone opening lequired to furnish one second reverberation time when the volume of
the chamber is known. This chart is for chambers with dimensions in the ratio of
2:3:4 1/2 only; however, in practice the areas of tone opening shown are generally
satisfactory.
The tone opening should be located in the largest wall surface of the chamber if
possible, and preferably near the center of the wall area,
INSTALLATION AND MAINTENANCE
The organ must be connected to a regulated-frequency source of the
voltage and frequency specified on the name plate. If the frequency is
not regulated the pitch of the organ will be irregular.
When a console is set up for operation the anchoring must be loosened so that
the generator will float freely on its spring suspension systen]. No damage
will result if this is not done, but the console "svill sound noisy, and the same
is true if the anchoring is loosened but the console is not level. If the console
is to be moved a long distance the anchoring should be tightened during such
moves.
Several different types of anchoring have been employed and instructions for
loosening and tightening the generator in any particular consoleare given on
the instruction card contained in the bench which accompanied that console.
Each power amplifier has anchoring which should be loosened on installation
and tightned for shipping. If the cabinet has a reverberation unit, it should be
locked before moving the cabinet and the fluid should be removed as instructed
on the card attached to the tone cabinet.
The tone generator is lubricated by putting oil into cups inside the console. It
is recoinmended that each cup be filled three-fourths full, {1 tablespoon) once
a year» using only the oil recommended for this purpose.
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