Sunday, 24 January 2021

Samsung LCD TV Monitor LT20A350-troubleshooting, factory mode and service mode

 

Samsung LT22A350, LT23A350, LT24A350, LT20A350, LT22A550, LT23A550, LT24A550, LT27A550.  Chassis: WDS2, WDS4

  Always respect voltages. While some may not be dangerous in themselves, they can cause unexpected reactions that are best avoided. Before reaching into a powered TV set, it is best to test the high voltage insulation. It is easy to do, and is a good service precaution.

It makes sense to avoid exposure to electrical shock.  While some sources are expected to have a possible dangerous impact, others of quite high potential are of limited current and are sometimes held in less regard.

Leakage Current Test

With the unit completely reassembled, plug the AC line cord directly into a 120V AC outlet. With the unit’s AC switch first in the ON position and then OFF, measure the current between a known earth ground (metal water pipe, conduit, etc.) and all exposed metal parts, including: metal cabinets, screwheads and control shafts.
The current measured should not exceed 0.5 milliamp.
Reverse the power-plug prongs in the AC outlet and repeat the test.

Troubleshooting

No Power

- The LEDs on the front panel do not work when connecting the power cord.
- The SMPS relay does not work when connecting the power cord.
- The units appears to be dead.

The IP relay or the LEDs on the front panel does not work when connecting the power cord if the cables are
improperly connected or the Main Board or SMPS is not functioning. In this case, check the following:
- Check the internal cable connection status inside the unit.
- Check the fuses of each part.
- Check the output voltage of SMPS.
- Replace the Main Board.

No Video (Analog PC signal)

- Check the PC source
- Check the Arsenal, Check the Main Chipset.
- This may happen when the LVDS cable connecting the Main Board and the Panel is disconnected.

No video (HDMI 1, 2, 3, 4 - Digital signal)

Audio is normal but no picture is displayed on the screen.

- Check the HDMI source.
- Check the HDMI switch, Check the Main Chipset.
- This may happen when the LVDS cable connecting the Main Board and the Panel is disconnected.

No Video (Tuner_CVBS)

- Audio is normal but no picture is displayed on the screen.

- Check the Tuner CVBS source.
- Check the Tuner, Check the Main Chipset.
- This may happen when the LVDS cable connecting the Main Board and the Panel is disconnected.

No Video (Tuner DTV)

- Audio is normal but no picture is displayed on the screen.

- Check the DTV source.
- Check the Tuner, Check the Main Chipset.
- This may happen when the LVDS cable connecting the Main Board and the Panel is disconnected.

No Video (Video CVBS)

- Audio is normal but no picture is displayed on the screen.

- Check the Video CVBS source
- Check the Main Chipset.
- This may happen when the LVDS cable connecting the Main Board and the Panel is disconnected.

No Video (Component)

- Audio is normal but no picture is displayed on the screen.

- Check the Component source
- Check the Main Chipset.
- This may happen when the LVDS cable connecting the Main Board and the Panel is disconnected

No Sound

- Video is normal but there is no sound..

- When the speaker connectors are disconnected or damaged.
- When the sound processing part of the Main Board is not functioning.
- Speaker defect.

Entering Factory Mode

To enter ‘Service Mode’ Press the remote -control keys in this sequence :
- If you do not have Factory remote – control.

Power Off > Info > Menu > Mute

How to Access Service Mode

Using the Customer Remote
1. Turn the power off and set to stand-by mode.
2. Press the remote buttons in this order; POWER OFF- INFO - MENU - MUTE to turn the set on.
3. The set turns on and enters service mode. This may take approximately 20 seconds.
4. Press the Power button to exit and store data in memory.
- If you fail to enter service mode, repeat steps 1 and 2 above.
5. Initial SERVICE MODE DISPLAY State.

x How to enter the hidden factory mode.
a. into the factory mode
b. move the tap to Advanced
c. key input : 0 + 0 + 0 + 0
xx hidden menu : Advanced

Buttons operations within Service Mode


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