LG LST-4200A Service Manual - Page 43

ATSC Front-End part

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6. ATSC Front-End part Start YES NO Is power charging normal(IC500)? YES Is RF input signal normal? NO (using spectrum analyzer) YES NO Check error signal (IC500(22)). (Oscilloscope is used) High : Normal, Low : Abnormal YES Check output data of tuner(IC500). NO (Fig. 01) (pin 28,29,30,31,32,33,34,35), packet clock ( Fig.02)(pin 27) and byte clock(pin 36) (Fig.03). YES END Check the power line, referring to circuit diagram. (+5V_Alive, +5V, +30V, +1.8, +3.3V) Check antenna connection condition. Check voltage between R511 and earth. 5V : Normal, 0~4V : Q501, Q502 should be replaced. Check connection between tuner and PCB. 3-34

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3-34
6. ATSC Front-End part
Is power charging normal(IC500)?
Is RF input signal normal?
(using spectrum analyzer)
Check error signal (IC500(22)).
(Oscilloscope is used) High : Normal,
Low : Abnormal
Check output data of tuner(IC500).
(Fig. 01)
(pin 28,29,30,31,32,33,34,35),
packet clock ( Fig.02)(pin 27) and
byte clock(pin 36) (Fig.03).
Check connection between tuner and
PCB.
END
Start
Check the power line, referring to
circuit diagram. (+5V_Alive, +5V,
+30V, +1.8, +3.3V)
Check antenna connection
condition.
Check voltage between R511 and
earth. 5V : Normal, 0~4V : Q501,
Q502 should be replaced.
NO
NO
NO
NO
YES
YES
YES
YES
YES