Farfisa Compact User Manual - page 27
Some explanation on schematics
SE
•
10: Operating
s
chemat
i
c
s
The schematics show the general principles, which are the following ones:
a) The signals are originated by oscillators
G
tO. Each one of them produces all the frequencies of same
name
(i.
e.
G
10
•
C produces all Cs
,
G
10 ·A prc:x:luces all As, etc,).
b)
The Vibrato is obtained operating directly on the oscillators of the various notes.
c)
Every key has three contacts: the lower one operates on 16' frequencies, the medium one operates on
· frequencies, the upper one operates on
4'
frequencies.
d) All the contacts related to every octave,
C
•
B, for 16' or
8' or 4', have common ends for connection to
filters; these ends are represented by common bars and each one them is connected by means of a shielded
cable to a series of switches operated by the MTB ON/OFF tab.
e) The MTB switches
are
meant to convey the signals to the tone stops when the MTB tab is in OFF
position. In this case, inserting one tone
stop (or several
stops at the same time), the signals are conveyed to
filter FD 10, where part of the signals is blended and then conveyed to filter FA 10 for the formation of the
sharp tones (oboe, trumpet, strings).
The signals proceeding from filter FA
tO
r
e
t
u
r
n to the tone stops and through the inserted tab,
they are
conveyed to the L.F.
p
r
ea
mplifier. At
the
same
time, in the filter
FD 10, an attenuation of the higher
harmonics,
interesting the
signals conveyed to
the
low pass filter, takes
place, giving way to an output of
sweet tune
signals, ready to
be
conveyed,
throug
the special tone s
to
ps
(bass, flute), to the
L. F. preampJif,ier.
f) When MTB
is inserted, the switches convey the signals
proceeding
from
the common
bars t
o filter
FD 10 through MTB stops
(
t6'.
8'. 4').
The
total
blending of signals in FD 10 is then conveyed directly to the
special in take of MTB, where
the
filtered
signals, available
at
the
outlet No. 10 of FD 10 (sweet tune) are con
veyed to the outlet
of MTB.
The L.F. preamplifier
is connected only to
the outlet
of MTB and amplifies therefore only the
signals c
on
·
veyed to this device through
t6'.
8' -4'
stops (Green
tabs) with the exclusion of the tone stops
(white tabs).
g) When
c
All Booster
»
is inserted, the signals
proceeding from the common bars are
permanently con·
veyed, at constant level, to filter FD-10 through MT6
st
ops 16',
8', 4'.
SE
•
II
:
Simplified keying schematics for Treble and Manual Bass.
It shows
the
wiring of the
various notes, making reference
to one note only (A).
SE
•
12:
Circuit diagram of Treble registers
The drawing reports the connections
interesting t
he tone stops and the connections between the registers
and the filters.
In
the left top
corner, framed in
a· square, it is shown
the schematic diagram of MTB device.
SE
•
13:
Circuit diagram of Pedal registers, Vibrato and Reverb.
The drawing showing the Manual Bass
a
nd
the
Pedalboard stops indicates the potentiometers for the volume
regulation of single notes, while the drawing related to Vibrato and Reverb shows Potentiometer R
536 for the
regulation of the time of Reverberation.
SE
•
14:
Schematics
of Master oscillators
(G 10),
filters
(FD 10), (FA 10), Vibrato
circuit and Pedal
amplifier (PS
10).
The schematics show the values of all components assembled in the printed circuits for repair purpose.
SE.
15:
Circuit diagram of Power Supply, Preamplifier and Reverb.
Complete electric schematis, showing the voltage rating and the
features of electric components. Almost
in the centre of the page it Is indicated the Swell Pedal photoresistor operating as volume control.
25