Yamaha CS-30 Service Manual page 28

CS-30(S/S 1001—)
5. PW, PWM Circuit
a. Switch the C6 key ON with FEET 1 (PSW2) at 16', MOD FUNCTION (PSW6) at
f\J
and MOD-
DEPTH (PVR9) at 10; the frequency should change between 965 and 1150Hz when 3.2Vp-p
P\J
wave is added to the
f\J
((§)—1.2) terminal (when the voltage at the
f\J
terminal is shifted bet¬
ween +1.6V and —1.6V, the frequency will vary between 965 and 1150Hz). At this time, if the MOD
—DEPTH (PVR9) is turned to the left little by little, the frequency variations become less and less; if
it is turned all the way to the left, the original frequency (1053.6 ± 1Hz) should appear.
b. Be sure the 3.2Vp-p f\J wave is added to the f\J (X —1 -2) terminal. When PWM1 (PVR7) is at 10,
the n 1 ((4)—7) terminal receives 90 — 10 ± 9% duty voltage. Then, when PWM 1 (PVR7) is return¬
ed to 0, then when PW1 (PVR5) is 90% the
PL
1 waveform duty voltage is 90 ± 9%.
10
%
90'
+ 1.6V
90?
-1.6V
o
Note: Inverted wave is fed out from
the rear panel OUTPUT.
When+1.6V input When-1.6V input
When PW1 is 90%
6
. Voltage Control Oscillator Circuit 2 (VC02) & Wave Convertor Circuit 2 (WSC2)
a. As in 4—(a), set FEET 2 (PSW3) to 4'. With the C6 key ON (KV terminal; 2.000V) adjust [VR 8) for
4215Hz at 2 (®-3) terminal.
b. Then, with the C
2
key ON (KV terminal; 250.0mV) adjust [ VR 7j for 526.8Hz.
Note: Repeat (a) and (b) above so that each frequency variation is within 0.1% even when switching.
c. As in 6—(a), check that the frequency is as indicated in the chart below when FEET 2 (PSW3) is
switched.
FEET
Frequency (Hz)
4' 4215
8
' 2107
16'
1053.6
32'
526.8
64'
263.4
128'
131.7
Note: The waveform shown below should be obtained at
the
PL 2
(®—
4)
terminal at the same frequencies
as f\ 2 terminal.
- +1.6±0.3 V
-0 V
- —1.6 ±0.3V
within ±0.1%
-
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