Electrical Troubleshooting Guide; Power(Smps) Circuit - LG LST-3100A Service Manual

ELECTRICAL TROUBLESHOOTING GUIDE

1. Power(SMPS) CIRCUIT

(1) No 5.0VA
No 5.0VA
YES
NO
Is the F101 normal?
YES
NO
Is the BD101
normal?
YES
NO
Is the R105
Normal?
YES
NO
Is Vcc (13V - 16V) sup-
plied to IC101 Pin7?
YES
NO
Are the D106
normal?
YES
NO
Is there about 2.5V
at the IC103 Pin1?
YES
NO
Is the D105
normal?
YES
NO
Is the D109
normal?
YES
NO
Is the D110
normal?
YES
NO
Is the D108
Normal?
YES
Replace the F101.
(Use the same Fuse)
Replace the
BD101.
Replace the R105.
Is the D103
normal?
NO
Check or Replace
the D106.
Replace the
D106.
Replace the IC103.
Replace the
D105.
Replace the
D109.
Replace the
D110.
Replace the
D108.
YES
Is the D107
Normal?
YES
Power Line of Main
PCB is short
(2) No 5.0V
NO 5.0V
YES
Is there about 5.4V
at the IC152 pin1?
YES
Is there about 3.3V~5V
at the IC152 pin4?
YES
Check the IC152
and Replace
(3) No 3.3V
No 3.3V
YES
Is there about 3.8V
at the IC153 pin1?
YES
Is there about 3.3V~
5V at the IC153 pin4?
YES
Check the IC153
and Replace
3-5
NO
Replace the
D107.
NO
Check or Replace
the D106
NO
Check the 'PWR CTL
"H"' signal from µ-com
NO
Check or Replace
the D105
NO
Check the 'PWR CTL
"H"' signal from µ-com