Yamaha CS-50 Servicing Manual page 71

2. TUNING VOLTAGE CIRCUIT
The D-A converter of the key assigner circuit includes a voltage network consisting of resistors for the purpose of
providing the analog voltage corresponding to the octave in which the note for tlie depressed key is included. To
this network,
+
lSV is applied as the reference voltage. If a voltage control circuit as illustrated is inserted to
between
+
lSV and the network, the analog voltage for each octave can be displaced in parallel, allowing the tuning
control.
+15
\
c
jvRnj
B~200
750
T03
I
VRIB
I
.A
3
~
1
TU I
Octave
l
2
I
voltage ladder
330
I
VRIA [
circuit
TO!
3l (KAS circuit board
1
o -
l
+15
300
5.1K
L~
.::::7
SUB circuit board
Tuning voltage circuit
PN
2
PITCH control
4.7K
VRIB= B~500Q
SUB circuit board
>!:>"
VR!A=B~IOKQ
IC.\<:!=IC!NJM4558 I
Yz
Buffer circuit
[Operation]
The reference voltage
+
lSV is divided by the tuning voltage circuit and the variable resistor of pitch control, and
the resultant
volt6!~~
is stabilized by the buffer circuit and applied to the octave voltage ladder network (KAS
circuit-board). This is the reference key voltage.
In this circuit, the voltage at the output terminal (0) can be varied from 3 to 6V by use of PITCH control on Panel
1. VRll (B-200.11) is adjusted so that 4V is given at 0 terminal when the PITCH control is positioned centrally.
The PITCH control is a dual variable resistor, consisting of coarse control (VRlA) and flne control (VRIB). (See
the illustrations below.)
Pitch control VR
Coarse control knob
Trifle control knob
~
a
-IH3~"'"~4•3~""
-500±100 cents +700±100 cents
(1200
cents~
l OCT)
62-------------------------~-------------------------------------------