Block Diagram - Casio EV-660C Service Manual

Adjustment procedures (EV-660C/I/N)
1. VCC2 adjustment, VCC7, VCC6, VCC5, VEE1 voltage check
• Condition
(1) Signal
No signal
(2) Other conditions
Power supply: Vcc1-1 = 5.00 ± 0.05 [V]
• Adjustment
Apply 5.00 ± 0.05 [V] on Vcc1-1.
Adjust VR100 so that Vcc2 (CP108) voltage becomes 4.80 ± 0.02 [V].
• Checking
VCC7 (CP105) = 27.1 ~ 33.4 [V]
VCC6 (CP106) = 18.0 ~ 20.0 [V]
VCC5 (CP107) = 11.0 ~ 13.0 [V]
VEE1 (CP109) = –12.0 ~ –10.0 [V]

• Block diagram

Stabilizer
2. LLD coil adjustment
• Conditions
(1) Signals
Broadcasting system: B/G
Color system: PAL color bar
(2) Signal level
Input electric field: 46 ± 3 dBµ (IF AGC full gain), P/S = 10 dB
(3) Other conditions
CCIR IF (Input electric field: terminated with 75 Ω resistance)
As to VIDEO signal, use signal source equivalent to TG7.
Power supply: Vcc1-1 = 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
Signal
generator
Stabilizer
L-PCB
VCC1-1
L-PCB
IF signal
Detector OUT
VCC1-1
Low-Pass Filter
VCC7
VCC6
VCC5
VCC2
VEE1
DC IN
Oscilloscope
— 4 —
Digital
V
Voltmeter
Adjust to minimize the DC level.