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2. Decoding integrated circuits TDA8844
TDA8844 is super large integrated circuit decoder, containing intermediate image
amplifying, intermediate sound amplifying, line and field scan, small signal processing,
color decoding, color brightness segregation, hipressure tracing and overload protection,
2
I C bus control, EW correction and automatic darkness adjustment.
Information introducing functions and testing data for TDA8844 maintenance is listed in
Table 2. Test information is listed beneath VHFL, if a cylindrical color card is installed
then a FLUKE 79 III meter is used.
33 Clearing recovery, low-level effective
4.3
3.7M
2.5M
34 +5V power supply
5
29K
21.8K
35 Neutral point
0
3.8M
2.4M
36 Remote control signal input
5
62K
38M
37 Grounding
0
0
0
38
Production control
5
33K
27K
39 Brightness and color segregation
control
0
24K
23.9K
40 AV1, AV2 and SVHS switching
control input
0
24K
23.8K
41 I
2
C serial bus clock line
3.9
31K
24K
42 I
2
C serial bus datum line
4.0
31K
24K
Table 2
Ground Resistance (R)
Step
Function
Working
Voltage
(V)
Positive
(
¦¸
)
Negative
(
¦¸
)
1
Secondary sound IF input
0
1.4
1
2
External sound frequency signal
input
3.7
6.2M
4.7M
3
Image IF PLL, not applied
0
~
~
4
Image IF PLL, not applied
0
~
~
5
RC filter connected for PLL circular
wave
2.5
6.2M
4.2M
6
Video frequency output
3
4.3M
4.7M
7
I
2
C serial bus clock line
3.9
31K
24.3K
8
I
2
C serial bus datum line
4
31K
24.3K
9
Trap decoupling
6.7
6.0M
4.1M
10
S-VHS C signal input
1.1
88.1K
87.7K
11
S-VHS Y signal input, front AV
video input
3.4
6.1M
4.5M
12
+8V power input
8
2.8K
2.8K
15