Bright Voltage Setting And Contrast Adjustment (Pcb-La); Color Adjustment (Pcb-La) - Casio QV-770 Service Manual

Bright voltage setting and contrast adjustment (PCB-LA)

• Signal contents
10STEP (NTSC)
Input oscillation level 0.5 Vp-p to VIDEO terminal (CP302).
• Voltage supply
VCL0 (CP101)=5 V ± 0.05 (V).
Apply 3.3 V± 5% to PW.
Connect PCB-LB and input.
(You can use an AC adaptor however, for the checking after repairs, apply above mentioned voltages.)
(1) Adjust VB waveform (CP324) as shown below by triggering FRP (CP305) signal.
(2) Adjust waveform A at 3.5 ± 0.05 V by adjusting RGB, AMP VR(VR302).
(3) Adjust contranst terminal voltage (CP306) at 1.5V ± 0.05V by adjusting contrast VR (VR303).
(4) Keep waveform B at 2.1 ± 0.05V by adjusting Bright VR (VR304).
(5) Keep waveform C at 2.9 ± 0.05V by adjusting contrast VR (VR303).
Note: • Make sure that waveforms are not distorted.
3.3 V
VCL0
Power
suppry
S G
VIDEO
(0.5 Vp-p)

Color adjustment (PCB-LA)

• Signal contents
Input oscillation level 0.5 Vp-p to VIDEO terminal (CP302).
• Set Power Supply
VCL0 (CP101) to 5.0 ± 0.05 V.
Apply 3.3 V ± 5% to PW.
Input HDB signal by connecting PCB-LB.
(You can use an AC adaptor however, for the checking after repairs, apply above mentioned voltages.)
(1) Adjust VR300 so that the first and fourth pulses of VB(CP324) signal will be the same.
Notes: • Perform this adjustment after contrast adjustment.
• Trigger FRP (CP305)
3.3 V
Power
VCL0
suppry
S G
VIDEO
(0.5 Vp-p)
QV-770
PCB-LA
PW
Waveform
(CP101)
VB
(CP324)
(CP302)
QV-770
PCB-LA
PW
(CP101)
VB
(CP324)
(CP302)
— 19 —
Waveform B
C
osilloscope
1 2 3 4
oscilloscope
Waveform
A