Hammond X-5 - LC Oscillator with Vibrato; Mod Generator

Q2THRDUGH 0.6
:
2
UNLESS OTHERW
ALL
RESISTORS .
MDD
GENERATOR-TWO
PACKAGE
SYSTEM
VIBRATOABLE
LC
Oscillator With Vibrato
Assembly MG-4(B)
includes a
vibrato
oscillator,
vibrato
circuitry, and
a high
frequency LC
oscillator
used to
drive the
MDD generator.
The vibrato
oscillator is a
phase shift type,
comprised
of C13, C14,
C15,
R16, R17,
R18, R19,
R20, R21,
VR1,
Q4, and
Q5. VR1
is used to
adjust
the
oscillator's frequency.
The vibrato
signal
is coupled
through C16, R22,
and CI 7 to the
base of
transistor
Q6,
where it is
amplified,-(lts
width being
controlled
by VR2.}.
Vibrato may be
turned oft by
connecting J202-1
to
-20V
(J202-3), and may
be
reduced for
"Vibrato I
or Vibrato
II" by
connecting R24
through J202-2
to
-2DV. To
achieve a
better sine
wave the
vibrato
signals is
filtered by C18
and is
then coupled to
the
LC
oscillator circuitry by C19.
The
LC
oscillator is
comprised
of
L, D1,
CI,
C2,
C3,
C4, R3,
R4, R5, and Q1,
and is a
Colpitts type. D3,
a
varicap diode, is
used to vary
the oscillator's
frequency for
vibrato and
tuning control; As
the
voltage at the
junction of R2, C1, an D1
becomes
more negative, the
capacitance
of the varicap diode
increases, and the
oscillator
frequency decreases.
Since
the cathode of
the varicap is
normally {with
no vibrato) at
ground potential
and the
anode
is
held at -5.6V
by D4 and R1,
the
capacitance of the
varicap
remains
constant, and
.stability
of the
oscillator is
maintained.
Capacitor CI is used to
isolate the D.C.
bias on the
varicap from
the tank
circuit. LI,
with
C3,
C4, C1
and the varicap
diode
oscillator at
4.0048
MHz.
R4
and R5 supply a
bias
voltage
for
Q1. The
oscillator
signal is
coupled
through
C5
to
buffer amplifier Q2
which drives
I.C. 1.
MDD Gene
I.C.
1, a si
input
sign;
the MDD
driven by
this I.C. is
by C7.
I.C. 2 and
I.C. 2 gen
"Cx" and
I.C.
3 doe
buffer
03
signal for
I