SAMSUNG D74A CHASSIS
Manual de Servicio

Troubleshooting

6-2-3 No Picture (When audio is normal)
Symptom - Audio is normal but no picture is displayed on the screen. - This may happen when the Main Board is normal but the X, Y Main Board, Logic Board, or Y Buffer Board is out of order. Major Checklist - The output voltage of the Main SMPS or the DC-DC SMPS is out of order. - This may happen when the LVDS cable connecting the Main Board and the Logic Board is disconnected.

Troubleshooting Procedures

Are the Vs and Va voltages No normal after removing the CN809 cable from the Main SMPS? Yes

Replace the Main SMPS

Is the output voltage of the DC-DC SMPS normal when reconnecting the CN809 cable and removing the CN1, CN2, CN4 and CN6 cables from the DC-DC SMPS? Yes Replace the Y Main Board

No

Replace the DC-DC SMPS

Replace the X Main Board

Replace the Logic Board

Replace the Y Scan Board

Caution

When separating and connecting the cables such as CN809 of the Main SMPS, CN1, CN2, CN3, CN4 and CN5 of the DC-DC SMPS, CN of the X Main Board, and CN of the Y Main Board, a spark may be generated by the electric charge of the high capacity capacitor. Therefore, wait some time after separ ating the power cord from the unit.

6-4

Samsung Electronics