Contrast And Brightness Voltage Setting Adjustment - Casio KX-787 Service Manual & Parts List

5-4. Contrast and Brightness voltage setting adjustment

1. Preparation
• AC adaptor or voltage regulator
• Digital oscilloscope
2. Adjustment procedure
(1) Start up Test mode Menu1.
1. Turn POWER on while pressing SHIFT key and MENU button simultaneously
2. Quickly press keys in the order of SHIFT key, SHIFT key and MENU key.
(2) Select / Execute GRAY SCALE (10 step). (NTSC)
(3) Trigger VG waveform (CP322) by FRP (CP300) signal to adjust as noted below.
(4) Adjust CONTRAST VR (VR306) so that contrast terminal voltage(CP302) signal is 1.50 ± 0.05 V.
(5) Adjust BRIGHT VR (VR303) so that potential between signal's pedestal and 4 step is 2.25 ± 0.05 Vp-p.
(6) Adjust CONTRAST VR (VR306) so that potential between signal's pedestal and 10 step is 2.85 ± 0.05
Vp-p.
(7) Remove the resistance set between the killer terminal (CP308) and the VCC5 (CP520).
3. Notes
• Consecutively, execute 5-5. TINT setting adjustment.
• Make sure that waveforms are not distorted.
4. Connection diagram
Power
Supply
pedestal level
VCC5
QV-2900
D-PCB
Killer terminal
(CP308)
Digital oscilloscope
VG(CP322)
Figure 2
— 19 —
22KΩ
Figure 2
2.25 ± 0.05 [Vp-p]
(pedestal – 4STEP)