Yamaha CS-30 Service Manual page 37

CS-30(S/2i 1001 ~)
LFO Circuit Board
1. LFO Oscillation Circuit
Turn EG—DEPTH volume (PV1) to 0 and SPEED control (PVR2) to S positions and adjust [vr
2
) to
provide terminal f\ ( 3 -8) with 0.1 ± 0.02Hz.
Then, adjust [VR l) to obtain 100 ± 2Hz when SPEED control (PVR2) is turned to F position.
LED indicator will glow according to the number of frequencies.
2. Waveform Conversion Circuit
a. The waveforms shown in Fig. 1, Fig. 2. Fig. 3 and Fig. 4 should be obtained at terminals |\ ( 3 -
8), (/ (X—7),
/\J
('3—9) and [~L ( 4 —1) respectively.
b. When LFO/NORMAL switch on TRIGGER is turned to LFO (0V at terminal N ( 4 -2) and the key
is turned ON (—7V is applied to terminal KTR ( 4 —3)), the waveform shown in Fig. 5 should be
obtained at terminal O |~T (3 —10) and its frequency should be one half (cycle time is two times
that of LFO oscillator.)
"T
14 ± 1 V
Fig. 5
3. Trigger Circuit
Terminal LTR C?}-7) should operate as shown in Fig. 4 under the following conditions:
\NNNNJ\T'' i_\rsr
LF0/N0R.N terminal ('4,-2) NOMAL
LFO
- -i
OFf| ON 1 OFF
KEY—ON .KTR terminal ( 4 3) —L-- 1-
ON j
LTR terminal ( 4 —7)
tna
am
+ 14 V
0 V
LED glows
JuuuuuLnjui
-
35
-