E3, E3D, Chassis - Panasonic TV Other Service Manuals (repair manual). Page 8

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8
3. 
Shading
Purpose :
To correct variations in the left and right shading due to
differences in the positions of the projection tubes, to
correct gamma and to blank the final sweep interval.
Shading Correction :
Horizontal parabola wave is made by horizontal plus via
Q7741-Q7744 and Q7745-7747.  H.SAW wave and
H.PARA wave is input to Pin No. 2 and 5 of IC7704, then
they are mixed in the IC7704 and then it is output from pin
No. 7 o IC7704.
The correction wave-form output from IC7704 is input to
pins 10 and 8 of IC7703, the R and B gain is adjusted, and
then the left and right brightness are varied to correct any
lack of colour uniformity on the screen.
4. 
Prevention of projection tube burn-out
Purpose :
This feature operates to prevent burn-out from occurring in
the phosphor substance of the projection tube when the
picture is stopped for an extended period.
Operation :
Each time the power is turned off, the channel is changed,
or AV input switching is performed, the screen display
position is moved and rotated horizontally and vertically
approximately 3 mm in a clockwise direction.
The MPU sends a command to move the screen display
position horizontally and vertically, to IC1309, through the
I²C Bus, for an input from the button on the TV, or from the
remote control, to turn the power on or off, or change the
channel, or switch the AV input.
A3
W2
7
IC7704
AN6142
H.SAW
Q7741
|
Q7744
HP-BLK
H.PARA
Q7745
|
Q7747
ADJ.
2
Q7748
7
5
10
8
19
18
20
IC7703
PA0057A
R-gain
B-gain
TPW101
TPW117
6
TPW2
+12V
R-out
G-out
B-out
(H.V)
(H+1.V)
(H.V+1)
(H+1.V+1)
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