![LG CM7420 Service Manual Download Page 55](http://html.mh-extra.com/html/lg/cm7420/cm7420_service-manual_220437055.webp)
3-36
ELECTRICAL TROUBLESHOOTING GUIDE
Power on.
FRONT board OK.
Check FFC cable (17P).
Check SMPS board.
Replace IC301.
Check FFC cable.
Check MAIN board.
Check SMPS board.
Replace LED
(LD3V01~LD3V8).
Check MAIN board.
Replace DIG301.
“HELLO”
Display on FLD
OK?
Volume LED
(LD3V01~LD3V8)
Turn on?
When turn
the volume, count is
change?
NO
NO
NO
NO
NO
NO
NO
NO
NO
CN301
cable connection
OK?
CN3V01
pin22 +12 V
OK?
Port P1~G15 of
DIG301 is OK?
CN3V01
pin23, 24 signal
OK?
CN301
Pin8, 9, 10 data signal
OK?
CN301
Pin15, 16, 17 power
OK?
2. SYSTEM PART
YES
YES
YES
YES
YES
YES
YES
YES
YES
Summary of Contents for CM7420
Page 13: ...1 12 MEMO ...
Page 15: ...2 2 MEMO ...
Page 19: ...A60 4 SPEAKER SECTION FRONT SPEAKER CMS7520F ...
Page 82: ...3 79 3 80 PRINTED CIRCUIT BOARD DIAGRAMS 1 SMPS P C BOARD TOP VIEW ...
Page 84: ...3 83 3 84 2 MAIN P C BOARD TOP VIEW ...
Page 85: ...3 85 3 86 MAIN P C BOARD BOTTOM VIEW ...
Page 86: ...3 87 3 88 3 FRONT_VFD P C BOARD TOP VIEW BOTTOM VIEW ...
Page 87: ...3 89 3 90 4 FRONT_MIC PORTABLE P C BOARD TOP VIEW BOTTOM VIEW ...
Page 88: ...3 91 3 92 5 FRONT_VOLUME P C BOARD TOP VIEW ...
Page 89: ...3 93 3 94 FRONT_VOLUME P C BOARD BOTTOM VIEW ...