Casio TV-880C Manual page 9

Adjustment procedures (TV-880D)
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
VCC1-1
Stabilizer
2. LLD coil adjustment
• Conditions
(1) Signals
Broadcasting system: I
Color system: PAL color bar
(2) Signal level
Input electric field: 40 ± 3dBµ (IF AGC full gain), P/S = 7 dB
(3) Other conditions
UK 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
IF signal
Signal
generator
VCC1-1
Stabilizer
VCC7
VCC2
L-PCB
VEE1
L-PCB
Detector OUT
Low-Pass Filter
— 7 —
Adjust to minimize the DC level.
DC IN
Oscilloscope
Digital
V
Voltmeter