Hammond Model A, Руководство пользователя, Страница: 125 / 298

SCHEMATIC DIAGRAMS
Figures 6, 7, 8 and 9 show four different vibrato circuits which have been used in
various models. As the components of different types are generally not
interchangeable, it is important the model and serial number be furnished when
ordering replacement parts.
Non-Selective Vibrato
Figure 6, used in all consoles with -V in the model designation, has a 25 section
vibrato line. It is wired (to minimize the number of compensated pick-off points)
so that the last part of the line is used for #1 vibrato. The vibrato switch has
positions for three degrees of vibrato (VI, V2 and V3) with three off positions
between them, and there is a separate vibrato chorus switch. A resistor connected
to the off side of the chorus switch serves to maintain constant volume for the
two switch positions. The switch is not intended to be left in its middle position.
The preamplifier used with this circuit is actually two separate cascaded amplifiers
on one chassis, with the vibrato system connected between them. The first section
drives the vibrato line, and the second section amplifies the signal picked up by
the scanner. The vibrato off contact in the vibrato switch carries non-vibrato
signal directly to the second section of the preamplifier. The complete schematic
circuit of a console of this type is shown in figure 7 of Section 2, and the
preamplifier in figure 6 of Section 16, Part 2.
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