No Bnc Video - Samsung 400UX-2 Service Manual

4. Troubleshooting

4-5. No BNC Video

-
Symptom The LED power turns on but the screen is blank when the BNC cable is connected.
-
Check the BNC cable connections.
Major
-
Check whether the LVDS cable is connected correctly to the panel.
checkpoints
-
Check whether the lamp connector of the panel is connected correctly to the SMPS board.
Diagnostics
Caution Make sure to disconnect the power before working on the SMPS board.
4-8
Does 5V appear at Pin 1 of CN302?
Yes
Is the cable connection correct?
Yes
Does the waveform as shown in the
image appear at Pin 6 (H-sync) 8 and
Pin 8 (V-sync) 9 of C304?
Yes
Does the TX** signal appear at
Pins 3 and 4 of FT604 and FT609
respectively?
Yes
Check the cable between the main
board and panel
and replace the LCD panel.
FT604 FT609
CN302
IC304
Check the circuits surrounding
No
Check the cable connecting
No
the BNC Sub board and the
No
Check the IC304.
The Scaler (IC303) is
No
abnormal. Replace the main
CN801.
Main board.a
board.