Circuit Explanation - Haier HT-3718 Service Manual

12.

Circuit Explanation

A1.HT-3718 color TV set composed of the following sections
(1) Small signal processing: super monolithic integrated circuits N201(TDA9361). and
memory N901 (AT24C08).
(2) Sound power amplifying: integrated circuits N301,N302 ( LA4285).
(3) Horizontal and Vertical scan output circuits: Vertical output integrated circuits
N801(TDA8357), Horizontal output transistor V902 (2SD1651), Horizontal flying back
transformer T902 (JF0501-19930).
Switch power supply: switch transformer T501 (BCK-08A5), power transistor N501
(4)
(5Q0765).
AV switch integrated circuits N401(HEF4053).
(5)
A2. Main integrated circuits:
(1) TDA9361
(2) LA4285
(3) TDA8357
A3. Electrical circuit analysis
1) Microprocessor and Small signal processing: super monolithic integrated circuits
TDA9361
TDA9361 is super large integrated circuit decoder, containing intermediate image
amplifying, teletext processing, intermediate sound amplifying, horizontal and vertical scan,
small signal processing, color decoding, hi-pressure tracing and over-load protection, I
bus control.
Information introducing functions and testing data for maintenance is listed in Table 1.
Table 1
Step
1. STANDBY
2. SCL
3. SDA
4. Tuning
5. SYSTEM
6. KEY
7. VOL1
8. VOL2
9. VSS C/P
Microprocessor
Picture IF/sound IF/video processing/H and V
Scan/color decoding
Vertical output integrated circuits
Sound power amplifying integrated circuits
Function
22
Working Ground Resistance(R)
Voltage
Positive
V
0.1 12.58K
3.5 12.62K
3.2 12.62K
0.4 0.5M
3.2 11.7K
3.1 33K
4.42 10.6K
4.42 10.6K
0 0
Circuit Explanation
2
Negative
12.87K
12.9K
12.9K
257K
11.9K
30K
10.9K
10.9K
0
C