Power Supply Section - Panasonic KX-F900 Service Manual

KX-F900
3-9. POWER SUPPLY SECTION
(1) Key components for troubleshooting
The following components have been known to break frequently :
F101, D101, Q101, IC101, D201, D202
This comes from our experience of experimental test. For example : power supply,
lighting 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 the fuse.)
If you do the fuse will melt again. It has not been repaired. The cause exists same where else.
Because of circuit compostion :
If 24V is not output, don't output.
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.
POWER SUPPLY BLOCK DIAGRAM
•, primary secondary .
AC INP_ Rectifier
circuit
Over
current
circuit
C°cnrveuir_ing
Q101
t
T101[
24v17
output
circuit
DC-DC
converter
circuit
Voltage feed
back circuit
OUTPUT
+24V
GND
-- +5V
DUMMY LOAD to check voltage
CN302
i
5V
1
25£2 <4 5V _+ 5%
2W :!
1200Q.
l W 24.5V + 4%
GND
24V
CN301
24V
24.5V + 4°/o (_
GND
5V+5% (
5V
(_ :VoltageMeter
-72-