LG LF-U850D Service Manual page 8

U-COM 5V VOLTAGE CHECK
SMPS ASSY CN943 -> 3PIN 5V OPERATION CHECK
YES
MAIN PCB PN101 3PIN 5VCHECK
YES
MAIN PCB PN304 5PIN 5.6VCHECK
YES
FRONT CN304 29PIN 5.6V CHECK
YES
U-COM 17,46,72,90PIN 4.7V~5V CHECK
MUTING CIRCUIT TROUBLESHOOTING (ON MUTE CONDITION)
HEAD PHONE MUTE CHECK
Q303 (A103S) BASE "HIGH" CHECK
YES
Q301, Q302,Q502,Q503(D1304S) BASE "HIGH" CHECK
YES
MUTE
NO
REFER TO SMPS TROUBLESHOOTING
NO
PN101 CONTACT STATUS CHECK
MAIN PCB PATTERN DISCONNECTION CHECK
NO
FFC WIRE ASSEMBLY STATUS CHECK
NO
FRONT PCB PATTERN DISCONNECTION CHECK
NO
-COM 10PIN (HIGH) OPERATION STATUS CHECK
C
Q303(A103S)OPERATION STATUS CHECK
REPLACE Q303(A103S) IF FAULTY
NO
REPLACE EACH APPROPRIATE TR
- 2-2 -
YES
YES
NO
C-COM 10PIN LINE CHECK AND U-COM
REPLACEMENT
YES
IC603(CS5340) 10PIN,12PIN INPUT CHECK
IC603(CS5340) 2PIN (MCLK), 4PIN (SDOUT), 7PIN
(SCLK), 8PIN (LRCK) OUTPUT WAVEFORM CHECK
YES