Yamaha CS-30 Service Manual page 27

CS-30(S/i: 1001—)
VCO Circuit Board
1. Tune Circuit
Set the TUNE knob to fully [—] position and [+) position, make sure that +75 ± 5mV and —75 ± 5mV
are respectively obtainable at TU (2)—1) terminal.
2. EG Modulator Circuit
Set the SEQ/KBD/EXT switch in Envelope Generator 2 to KBD position, AT, DT, RT to S, SL to 10,
EG—SELECTOR (PSW1) to C position, EG—DEPTH (PVR3) to 10 and turn a key ON, make sure that
0.8V is obtainable at EG (CD—13) terminal. (+8V Envelope voltage waveform is fed into C
(CD—
78)
terminal.)
Turn the DEPTH (PVR3) knob to the left gradually and make sure the voltage at EG terminal is gradual¬
ly diminished, resulting in 0 ± 0.1V when the knob >s fully turned to 0 position.
3. DE-TUNE Circuit
a. Put the isoration plug into KEYVOLT—IN (J5) on rear panel, connect the KV
(%
;—9, 10) terminal to
EK (2)—1 ~ 4) terminal with jamper wire and set the MOD VC02 (PVR4) to 0, then adjust (VR 1
so that 0 ± 50mV or less is obtained at CPI.
b. Under the condition of item 3-(a), adjust (VR2] so that 0 ± 50/iV or less is obtainable at CP2.
c. Remove jamper wire and isoration plug next. Let SEQ/KBD switch (PSW4, 5) at KBD, set EG —
DEPTH (PVR3) to 0 and turn C6 key ON after TU ( X -1) terminal is set to 0.000V by TURN
Volume, (at the time there is 2.000V at KV terminal.)
When CP2 is set at 2.000V by DE-TUNE volume make sure that there is 2.000V at IC6, 7 second pin
and also is 166.8mV at IC6, 7 second pin when F
2
key is ON.
4. Voltage Control Oscillator Circuit 1 (VCOI) & Wave Shape Convertor Circuit 1 (WSC1)
a. Set both VCOI and VC02 SEQ/KBD switches to KBD side, MOD DEPTH (PVR9, 10) are 10, FEET
1 (PSW2) at 2'and turn the TUNE (PVR1) volume untill 0.000V is present at TU (1—1) terminal.
Then adjust DE-TUNE (PVR2), when F
2
key is pressed, so that the voltage at CP3 is same as that of
CP4 (166.8mV). Next, make sure that voltage of 2.000 ± 0.001V is present at CP3 during C6 key is
ON.
b. After the above setting is completed, adjust [VR
4
! to achieve r\ 1 (
4
»—6) terminal output fre¬
quency of 8429Hz when the C6 key is ON (KV terminal is 2 ± 0.001V).
c. Adjust [VR
3
) to achieve 1053.6Hz when the
C
3
key is ON (KV terminal is 250 ± 0.1 mV).
Note: Repeat (b) and (c) above so that each frequency variation is within 0.1% even when switching.
d. Check that the frequency is in accordance with the chart below when FEET 1 (PSW2) is switched, as
in 4—(b) (i.e., MOD-DEPTH, PWM1, PW1 are 0 and 50%).
FEET Frequency (Hz)
2' 8429
4'
4215
8'
2107
16'
1053.6
32' 526.8
64' 263.4
within ±0.1%
Note: The output indicated below should be present at the
fT 1 ((
4
')—7) and
f\]
1 (C.4)—5) terminals when
the frequency is the same as the f\ 1 terminal.
/
+ 1.6 ± 0.3 V
0 V
— 1.6 ± 0.3V
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