Casio SY-20B, Руководство по обслуживанию, Страница: 6 / 19

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Adjustment procedures
1. Vcc2 adjustment, Vcc7, VEE1 voltage check
•
Condition
(1) Signal
No signal
(2) Other conditions
Power supply: Vcc1-1 (CP101) = 5.00
±
0.05 [V]
•
Adjustment
Apply 5.00
±
0.05 [V] on Vcc1-1 (CP101).
Adjust VR100 so that Vcc2 (CP102) voltage becomes 4.00
±
0.02 [V].
•
Checking
Vcc7 (CP103) = 36.0 ~ 44.0 [V]
VEE1 (CP104) = –4.50 ~ –6.00 [V]
•
Block diagram
2. LLD coil adjustment
•
Conditions
(1) Signals
Broadcasting system: M/M
Color system: NTSC color bar
(2) Signal level
Input electric field: 40
±
5 dB
µ
(IF AGC full gain), P/S = 10 dB
(3) Other conditions
US IF (Input electric field: terminated with 75
Ω
resistance)
Power supply: Vcc1-1 (CP101) = 5.00
±
0.05 [V]
•
Adjustment
Monitor video detection signal (CP238) via a low-pass filter of 100 kHz cutoff frequency and adjust LLD coil
T200 so that its DC level is minimum (waveform’s amplitude is maximum).
•
Confirmation
There should be no waveform distortion (erroneous synchronization, etc.), under sensitivity (video detector
output level is abnormally small, etc.).
•
Block diagram
V
Digital
Voltmeter
L-PCB
Stabilizer
Vcc1-1
Vcc7
Vcc2
VEE1
Vcc1-1
IF signal
L-PCB
Adjust to minimize the DC level.
Oscilloscope
DC IN
Detector OUT
Signal
generator
Stabilizer
Low-Pass Filter