LG MW-30LZ10 Service Manual - Page 6

TROUBLESHOOTING Symptom 1. No power from all outputs Cause 1) Fuse open 2) Error of rectying circuit/EMI Filter 2. No power from +24V/+12V /+18V 1) Short of output terminal 2) Input error of parts 3) Error of U902 and peripheral circuits. Check Point 1) Check BD801, Q801, Q802, Q804 2) Check BD801, L801, L802, TH800, TH801 1) Check the second side parts and Pattern short 2) Check reverse input of PH801, D916, CR802 3) Check R941~R944 when the Pin Bias power no7. of U902 is abnormal. (normal: 15V~25V) - Replace U902(FAN7554) parts - Check the error of Q804 3. No power from +18V 4) Error of T803 1) Short of output terminal 2) Input error of parts 3) Error of U802 and peripheral circuits. 4) Replace T803 1) Check the peripheral parts of 18V and Pattern short. 2) Check reverse input of D916(SB560) 3) No Input of L812 when both terminal voltage of C830 are low. (normal voltage: +24V) - Replace U802(PQ1CG203) parts when there is no error. 4. No power from +5VS 1) Short of output terminal 2) Input error of parts 3) Error of U903 and peripheral circuits. 1) Check the peripheral parts of 5VS and Pattern short. 2) Check reverse input of D802, CR801 3) Check R937~R939 when the Pin Bias power no7. of U903 is abnormal. (normal: 15V~25V) - Replace U903(FAN7554) parts - Check the error of Q802 4) Error of T802 4) Replace T802 5. No power from +24V/+12V 1) Drop of output power due to the error /+18V in 110VAC Input of PFC circuit. 1) Replace U901(MC33368D) when there is no error in the peripheral parts. - Check the error of Q801 2) Error of T801 2) Replace T801 -6-