Yamaha CS-30 Service Manual page 29

CS-30(S/# 1001-)
7. PW, PWM Circuit
a. Switch the Ce key ON. the FEET 2 (PSW3) to 16'. MOD FUNCTION (PSW7) to /V and MOD-
DEPTH (PVR10) to 10. When a 3.2Vp-p
f\J
wave is fed to the
f\J
((6)—1.2) terminal the fre¬
quency should shift more than 970 1160Hz (when the voltage at the
f\J
terminal is shifted
between +1.6V and —1.6V the frequency will vary between 970 and 1160Hz). At this time, if the
MOD—DEPTH (PVR10) 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 (1053.6Hz) should appear.
b. Check that a 3.2Vp-p
f\J
wave is added to the
f\J
((D—1.2) terminal. When PWM2 (PVR8) is at
10, the n 2 terminal (@—4) receives 90^ 10 ± 9% duty voltage. Then, when PWM2 is returned to
0 and PW2 (PVR6) is at 90%, the f~L 2 waveform duty voltage is 90 ± 9%.
Note: Inverted wave is fed out from
the rear panel OUTPUT.
When +1.5V input When -1.6V input
When PW2 is 90%
8
. FM Modulation Circuit
a. Set the MOD—VC02 (PVR4) to 10. Then, when the C6 key is switched ON (KV terminal; 2 ± 0.001
V) adjust (VR 6) at TP1 for a value according to Fig. 1.
Now, when the C
3
key is switched ON (KV terminal; +250 ± 0.1 mV), adjust (VR 5] according to Fig.
2
.
Repeat these adjustments, making sure there is no deviation in the adjusted value, even during
switching.
b. Switch the C6 key ON (KV terminal, +2 ± 0.001V). When MOD-VC02 (PVR4) is set to 0, +2 ±
0.002V should appear at TP1. In this condition, when DE—TUNE (PVR2) is at the 1+] side, +3 ±
0.1V should appear at TP2; when it is at the [—] side, +1.5 ± 0.1V should appear.
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