Casio QV-770, Service Manual

Page: 20 / 46

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BL drive voltage adjustment
• Voltage supply
VCL0 (CP101)=5.0
±
0.05[V]
Apply 3.3 V
±
5% to PW.
(You can use an AC adaptor however, for the checking after repairs, apply above mentioned voltages.)
(1) Apply 5.0
±
0.05 V to VCL0 and adjust VR900 so that CP901(VBL) will be 6.1
±
0.1 V.
Notes: • Make sure that the current consumption is not abnormally large.
• CN920 is open.
VCOM AC adjustment and VCOM DC coarse adjustment (PCB-LB)
• Voltage supply
VCC2 = 5 V
±
0.05 (V) (CP181).
VCC8 = 13.5
±
0.05 (V) (CP180).
VEE2 = –15.0
±
0.05 (V) (CP182).
(You can use an AC adaptor however, for the checking after repairs, apply above mentioned voltages.)
(1) Make sure that the amplitude of VCOM output (CP771) is 6.6
±
0.3 V.
(2) Adjust VR770 so that the potential of VCOM output (CP711) will be 4.8
±
0.2 V.
PCB-LA
(CP901)
VBL
VCL0
QV-770
A
V
3.3 V
PW
(CP101)
Power suppry
PCB-LB
(CP771)
VCOM
0 [V]
–1.8 [V]
(CP180)
(CP182)
(CP181
high level
4.8 [V]
amplitude
6.6 [V]
VCC8
QV-770
VCC2
VEE2
Power
suppry
oscilloscope