Samsung PS42B451B2WXXU Service Manual page 38

Troubleshooting
■ ■ No Picture (When audio is normal)_42"
Symptom - Audio is normal but no picture is displayed on the screen.
- This may happen when the Main Board is functioning but the X, Y Main Board, Logic Board, or Y Buffer
Boards are not.
Major Checklist
- The output voltage of the Main SMPS.
- This may happen when the LVDS cable connecting the Main Board and the Logic Board is disconnected.
Troubleshooting
Procedures
When separating and connecting the cables such as CN810, CN809, CN807 of the Main SMPS, CN4701 of the
Caution X Main Board, and CN5707 of the Y Main Board, a spark may be generated by the electric charge of the high
capacity capacitor. Therefore, wait some time after disconnecting the power cord from the unit.
4-6
Check the LED operation of Logic Board
Is it normally operating?
Yes
Check the output of LVDS
Is it normally operating?
Yes
Check the each output of the SMPS
Is it normally operating?
Yes
Check the each output of the SMPS after
disconnecting the power
cable from SMPS.
And replace X-main, Y-main Board,
Y-scan Board.
No
Replace the Logic Board
No
Replace the Main Board
No
Replace the SMPS
No
Replace the Y Scan Board
Samsung Electronics