Samsung AP500PF Service Manual page 23

5-3 Fault Analysis by Symptom
5-3-1 No Power (No display)
1) Checkpoints
(1) Is the voltage of the power source normal?(AC 187V - AC 253V)
(2) Is the power line in good contact?
(3) Check the power fuse(F701, F702) and PCB fuse(F101) for open.
(4) A re the primary and secondary sides of the power-trans in good contact with the connector?
(5) Is the output voltage of REG1(KA7812) normal?(DC 11.5V - DC 12.5V)
(6) Is the output voltage of REG2(KA 7805) normal?(DC 4.5V - DC 5.5V)
2) Checking pro c e d u res(after checking the checkpoints of clause 1)
Turn off the power, and then turn it on in 5 seconds.
Is the room temperature displayed on the temperaturre
indicator, the display lamp turned on, and the panel
shutter down when pressing the on/off button.
Is the voltage or the power trans AC 18V-21V secondary
Is the output voltage of REG1 and REG2 normal?
Is the output wave at the MICOM(IC1) pin (No. 33~40) a
Is the output wave at IC4 pin No. 13~18 a square wave?
Is the harness between the main PCB and panel PCB well
LED display or panel PCB defective.
5-2
N
side(CN11) normal?
Y
(REG1=12V, REG2=5V)
Y
square wave?
Y
Y
connected?
Y
Y
Then it is normal operation.
N
Check and replace the power trans.
Remove the shorted parts of the
N
power terminal.
Replace the defective parts.
(D101-104, REG1, REG2)
N
Check and replace the MICOM(IC1).
N
Check and replace the IC4.
N
Reassemble or replace the harness
after checking it.
Samsung Electronics