Casio KX-723C, Service Manual & Parts List

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TFT-LCD
Y1
Y2
Y3
Ym
GND
Vy
Va
Vb
t1 t2
t3
X1
X2 X3 X4 Xn
Gate electrode
Picture
element A
Source electrode
TFT array substrate
Common substrate
Frame period
Selective period
Picture
element
A
Gate
pulse
T1
T2 T3 T4
Tn
Common
electrode
V COM
X1
Y3
Y2
Y1
t1
Each picture element electrode is controlled by a transistor. To the gate electrodes, the gate pulse is applied
timesharing. VCOM voltage is applied to the common electrodes.
The above figure shows the operation of TFT-LCD. If the gate pulse is not applied to the gate electrodes,
the transistors do not operate even when the potential difference is given between the common electrodes
and source electrodes, and no effect is given to the liquid crystal. If the gate pulse is applied to Y1, the
transistorT1 is in operation during a priod of t1, and voltage of source electrode of Va is applied to the LCD
layer of picture element A, then electric charges are stored in the picture element of A. After the period of
t1, T1 is turned off, and voltage in the LCD layer of A is held until next gate pulse comes, but it drops little
by little through off leak resistance of TFT and leak resistance of LCD itself.
BACK LIGHT
The camera unit is equipped with a fluorescent light source to provide the back lighting for its LCD. The
normal service life of the backlight is approximately six years, when the camera is used for about two hours
a day.
The backlight is consumption items, so even under guarantee replace it under charge basis.