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5-2

Samsung Electronics

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 voltage or the power trans AC 18V-21V secondary

side(CN11) normal?

Is the output voltage of REG1 and REG2 normal?

(REG1=12V, REG2=5V)

Is the output wave at the MICOM(IC1) pin (No. 33~40) a

square wave?

Is the output wave at IC4 pin No. 13~18 a square wave?

Is the harness between the main PCB and panel PCB well

connected?

LED display or panel PCB defective.

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.

Then it is normal operation.

Check and replace the power trans.

Remove the shorted parts of the

power terminal.

Replace the defective parts.

(D101-104, REG1, REG2)

Check and replace the MICOM(IC1).

Check and replace the IC4.

Reassemble or replace the harness

after checking it.

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