Panasonic KX-FT21BX, Service Manual

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KX-FT21LA
- 74 -
Input
Circuit
AC
Input
Surge
absorber
circuit
G
H
8V
24V
Kick-on
Voltage
Circuit
E
F
GND
Control
Circuit
Over
Current
Circuit
R102
R103
R104
Converter
Circuit
C
D
8V
Output
Circuit 5V
3 Terminals
Regulator
24V
Output
Circuit
+
-
Rectifier
Circuit
A
B
C106
Error Detecting
Circuit
POWER SUPPLY BLOCK DIAGRAM
DUMMY LOAD to check voltage
V : Voltage Meter
If there is no dummy load,
connect the main P.C.B.
with the analog P.C.B.
Surge
absorber
circuit
( )
1
2
3
4
5
6
7
8
V
V
GND
5V
24V
CN301
24.5V–0.4V
5V–0.25V
1.2k
2W
33
2W
Over
Voltage
Circuit
3-9. POWER SUPPLY SECTION
(1) Key components for troubleshooting
The following components have been known to break frequently :
F101, D101-D104, C109, Q101, PC101, ZD203, R302.
This comes from our experience with experimental tests. For example : power supply,
lightning surge voltage test, withstanding voltage test, intentional short circuit test, etc.
Caution:
If you find a melted fuse in the unit, don't turn the power on without repairing the unit first. (Except for the fuse.)
If you do, the fuse will melt again and the unit has not been repaired. The problem exists somewhere else.
In most cases, (our experience) the symptom is that nothing is output.
There is a high possibility in the primary side more than the secondary side.