LG LF-U850D Service Manual page 10

AUX FUNCTION
YES
JK601 CONTACT STATUS CHECK
YES
IC601 (BU4052)4,11PIN INPUT WAVEFORM CHECK
YES
IC601 (BU4052)3,13PIN OUTPUT WAVEFORM
CHECK
YES
IC602 (MC4580) 2,6PIN INPUT WAVEFORM CHECK
YES
NORMAL OPERATION
U-COM (IC301)83PIN,84PIN COMMUNICATION CHECK.
NO
MAIN PCB PATTERN DISCONNECTION CHECK
IC601 (BU4052)16PINVDD,8PIN VSS POWER
NO
CHECK
REPLACE APPROPRIATE PARTS
NORMAL
IC602 (MC4580) 4PIN VSS,8PIN VDD POWER
NO
CHECK.
REPLACE APPROPRIATE PARTS
NORMAL
NO
- 2-4 -
YES
YES
YES
YES
FRONT CN304 MAIN PCB PN302 FFC
WIRE contact and assembly
YES
NORMAL
REFER TO SMPS
TROUBLESHOOTING
REPLACE FAULTY PARTS