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IC Block Diagrams
IC001 < Audio AMP. > LA4285
+
INT
1 F
+
EXT
1 F
IC501 < Vertical Output > LA7840
Protection Circuit
This TV set has a built-in power supply protection circuit.
It is provided to protect the TV set in case of a power supply circuit malfunctions. When something abnormality
occurs during TV reception, the TV set goes to the stand-by mode.
When an abnormality occurs during TV reception, it causes pin 27 of the CPU to go continually Low(less than
0.75V) for about one second. The CPU detects that this has occurred and outputs the signal from pin 31 to
switch off the power supply lines.
Releasing the protective circuit and restoring power supply
To release the protective circuit and restore power supply, turn the power to the TV set OFF and then ON again
via either the main power switch or the ON-OFF button on the remote control. This will work only if the power
supply trouble was temporary. If there is permanent trouble such as a damaged circuit, power cannot be
restored and the circuit will have to be repaired.
A
B
1
2
3
4
INT/EXT
PRE GND
SW
DC VOL
THERMAL
PROTECTION
LA7840
LA7841
2
1
3
VCC
+
10
DC VOL
AMP
6
5
7
8
+5V
0.1 F
+
+
10 F
47 F
1.0
D. C
NF
POWER GND
PUMP
UP
-
AMP
+
7
6
4
5
-6-
1000 F
9
POWER OUT
+
100 F
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