Fault Diagnosis By Symptom; No Power - Samsung AQ12?5(6)MB Service Manual

5-2 Fault Diagnosis by Symptom

5-2-1 No Power (completely dead)-Initial diagnosis
1) Checklist :
(1) Is input voltage normal?
(2) Is AC power linked correctly?
(3) Is output voltage of DC regulator IC KA78L05 (IC02) normal? (4.5VDC-5.5VDC)
2) Troubleshooting procedure
YES
Is DC voltage of PCB
display normal?
Is rating voltage ±10% range
Replace PCB
applied to the primary side(~,~)
display
of the "BD71"
•Check linkage between
power cord and
terminal tap
•Check fuse
Is 325VDC appear in the
secondary side (+, -)
of "BD71"
NO
Replace
SMPS PARTS
Replace resonator (X301)
Is operation normal?
OK
5-2
Remove power cord and plug in
again in approx. 5 seconds
Is operation lamp blinking?
NO
Does operation start when
ON/OFF button on the remote
NO
Is transmission display of the
remote controller unit blinking?
Is "beep"sound heard from the main
NO
NO
Is DC voltage of the PCB module
Are voltages of #33 (compressor),
#36(4 way valve) and #34 (outdoor fan)
of the micom normal? 5VDC
Is voltage of #32 (indoor fan) of the
DC5V
YES
Is voltage at #10 terminal of the Micom normal?
Is voltage at #9 terminal of the Micom normal?
Is voltage at #3 terminal of the micom
Are voltage at #11 and #12 of the
NO
NO
YES
YES
controller unit pushed?
NO
YES
unit?
YES
normal?
YES
micom normal?
NO
0VDC
5VDC
YES NO
normal?
10ms
YES
NO
micom normal?
250ns
YES
Replace
micom
YES
Normal
NO
Refer to remote control
unit fault diagnosis
Replace PCB
NO
module.
Are voltages at RY71(Compressor)
YES and RY72(Outdoor FAN) normal?
DC12V Is voltage at SS71(indoor fan)
YES
Check connections
compressor and
outdoor FAN
and indoor fan.
Is output voltage of ICO2 normal?
YES
Check PCB pattern.
Replace main PCB.
Is voltage output terminal of
PC814(PC02) normal?
YES
Replace PC814(pc02)
OK
Samsung Electronics
NO
Replace
RY71 and RY72
and SS71
NO
Replace ICO2
NO