Casio TV-880C - Tv-880 C;I;N

— 4 —
L-PCB
DC IN
Oscilloscope
VCC1-1
IF signal
Stabilizer
Detector OUT
Low-Pass Filter
Adjust to minimize the DC level.
Signal
generator
Adjustment procedures (TV-880C/I/N)
1. VCC2 adjustment, VCC7, VEE1 voltage check
• Condition
Power supply: Vcc1-1 = 5.0 ± 0.05 [V]
• Adjustment
Apply 5.0 ± 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) = –4.5 ~ –5.5 [V]
• Block diagram
2. LLD coil adjustment
• Conditions
(1) Signals
Broadcasting system: B/G,H
Color system: PAL color bar
(2) Signal level
Input electric field: 40 ± 3dBµ (IF AGC full gain), P/S = 10 dB
(3) Other conditions
CCIR IF (Input electric field: terminated with 75-ohm resistance)
Power supply: Vcc1-1 = 5.0 ± 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).
(Reference: C= 1500 pF, R = 1 Kohm)
• Confirmation
There should be no waveform distortion (erroneous synchronization, etc.), under sensitivity (video
detector output level is abnormally small, etc.).
• Block diagram
V
VCC7
VCC2
VEE1
L-PCBStabilizer
VCC1-1
Digital
Voltmeter