31
CIRCUIT EXPLANATION
1. Principle Integrated Circuits
A1. BH2004D color TV set composed of the following sections
(1) Small signal processing: super monolithic integrated circuits N204
(LA76814A), and memory N901 (AT24C08).
(2) Sound power amplifying: integrated circuits N701 (LA4225).
(3) Horizontal and Vertical scan output circuits: Vertical output integrated
circuits N402 (LA78040), Horizontal output transistor V411 (TT2140),
Horizontal flying back transformer T402 (JF0501-19810).
(4) Switch power supply: switch transformer T501 (BCK-01-90I), power
transistor V503 (2SD4460).
A2.
Main integrated circuits:
(1) LA76814A
Microprocessor
Picture IF/sound IF/video processing/H and V
Scan/color decoding
(2) LA78040
Vertical output integrated circuits
(3) LA4225
Sound power amplifying integrated circuits
A3.
Electrical circuit analysis
1. Microprocessor and Small signal processing: super monolithic integrated
circuits, LA76814A.
LA76814A 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
2
C bus control.
Information introducing the functions and testing data for maintenance is listed in
Table 1.
1.
N701 LC863424B
PIN Leads
Function Voltage
(V)
PIN Leads
Function Voltage
(V)
1
Auto adjust Enable
Pin
5.1
19
OSD red signal output
0.09
2
Blank
20
OSD greem signal output
0.09
3
IIC data
4.6
21
OSD blue signal output
0.09
4
IIC clock
4.5
22
OSD blank signal output
0.01
