Chassis, Euro-5VP - Panasonic TV Other Service Manuals (repair manual). Page 5

Read Panasonic Chassis / Euro-5VP Other Service Manuals online

5
2.  Single ABL
Purpose :
In a normal TV the ABL operation detects the current
following to the secondary coil of the flyback transformer
and controls the contrast. In a video projection TV,
however, the current for the secondary coil of the flyback
transfomer is measured as the total current for the three
projection tube. Therefore the current can not be controlled
even if most of the electron beams are sent though one
projection tube. For this reason the monochrome ABL
circuit detects the maximum current for each projection
tube and controls the same. We have added a circuit which
accelerates the ABL operation time, and lowers the
contrast.
Operation :
In normal ABL operation detects the current flowing to FBT
which supplies the high voltage to the three projection
tubes, as with a standard TV. This is alike EURO5 chassis.
The current flowing to each projection tube is detected in
the colour output transistor emitter, and the maximum
current to each projection tube is then input to the Q7735
through D3352,D3362 and D3372.
Then output value of Q7735 is input to pin No. 5,7,9 and 11
of IC7705, these are compared with pin No. 4,6,8 and 10 of
IC7705.
Compared result is output from pin No..1,2,13 and 14 as
P0, P1, P2 and P3. P0-P3 data are input to IC7702, then
CRT current following is separated to 5 levels/ Ranks in the
IC7702 as follows.
P0
P1
P2
P3
RANK
LEVEL
H
H
H
H
A
Danger
H
H
H
L
B
I
H
H
L
L
C
I
H
L
L
L
D
I
L
L
L
L
E
Safety
Detection data is input to MPU through IIC bus line and
MPU controls the contrast to keep detection level safety.
R,G,B  OUT
Q7735
D3352,D3362,D3372
CRT-Anode
FBT
Q9601
4
5
7
6
8
9
11
10
2
1
13
14
+5v
IC7705
M5234P
IC7702
CX1315P
10
9
2
1
14
15
69
70
IC1101
MPU
IC9601
VCJ
43
11
10
BCL
SDA
SCL
+
-
+
-
+
-
+
-
E10 A10
16
1
P3
P2
P1
P0
LG1 W3
8
IIC bus
Q3351
Q3361
Q3371
Page of 13
Display

Click on the first or last page to see other Chassis / Euro-5VP service manuals if exist.