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11. Circuit Explanation
1. Principle integrated circuits
A1. HTN20R15 color TV set composed of the following sections
(1) Small signal processing: super monolithic integrated circuits N201(OM8377). and
memory N202 (AT24C08).
(2) Sound power amplifying: integrated circuits N601 ( AN7523).
(3) Horizontal and Vertical scan output circuits: Vertical output integrated circuits
N301 (TDA8357), Horizontal output transistor V401 (TT2140), Horizontal flying
back transformer T444 (BSC25-0283G).
(4) Switch power supply: switch transformer T801 (BCK-05E), power transistor N801
(KA5Q0765RT-YDTU).
A2.
Main integrated circuits:
(1) OM8377
(2) TDA8357
(3) AN7522 / AN7523 Sound power amplifying integrated circuits
A3.
Electrical circuit analysis
1、Microprocessor and Small signal processing: super monolithic integrated circuits ：
OM8377
OM8377 is super large integrated circuit decoder, containing intermediate image
amplifying, intermediate sound amplifying, horizontal and vertical scan, small signal
processing, color decoding, hi-pressure tracing and over-load protection, I
control.
Information introducing functions and testing data for maintenance is listed in Table 1.
2. ICs functional description
UOC OM83XX
SYMBOL
STAND BY output.
SCL
SDA
TUNING
P3.0/NTSC SW
Microprocessor
Picture IF/sound IF/video processing/H and V
Scan/color decoding
Vertical output integrated circuits
PIN
1
In STAND BY mode, high level (Power OFF).
For Power ON this pin will be reduced to low.
2
2
I
C-bus clock line
2
3
I
C-bus data line
4
tuning Voltage (Vt) PWM output
5
Port 3.0 or NTSC output/SCART SW input, Forced NTSC selection, Low-level
output, otherwise High output.
Circuit Explanation
DESCRIPTION
2
C bus
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