Tech Troubleshooting – LED LCD TCON and panel Troubleshooting

Model: LCD, LED

Symptom: There are vertical lines in the top right part of the screen.

Solution: The LVDS cable can cause this symptom if it is not seated correctly. Check the position of the LVDS cable and the contacts. If it is seated correctly and you still see vertical lines, replace the LVDS cable.

Model: LCD, LED
Symptom: There are two RED vertical bars and RED smears around objects.

Solution: The LVDS cable can cause this if it is not seated correctly. Check the position of the LVDS cable and the contacts. If it is seated correctly and you still see red bars and smears, replace the LVDS cable.

Model: LCD,LED
Symptom: There are horizontal black and white bars across the screen in RF ONLY

Solution: As you can see, the OSD is not affected. That tells you that the panel is OK. Replace the main board.

Model: UN55C8000XFXZA
Symptom: The right side of the screen is darker than the left.

Solution: Bring up the Test Picture. If the symptom affects the Test Picture, replace the panel.

Model: LCD, LED
Symptom: There are vertical lines in the picture.

Solution: The LVDS cable can cause this symptom if it is not seated correctly. Check the position of the LVDS cable and the contacts. If it is seated correctly and you still see vertical lines, replace the LVDS cable.

Model: PN42C430A1DXZA
Symptom: The picture has blemishes.

Solution: If the symptom affects the Test Picture, replace the panel.

Model: LNT5271
Symptom: The right side of the screen has horizontal lines.

Solution: In the example above, the line distortion is affecting the menu. Bring up the OSD menu. If the symptom affects the menu, replace the T-Con board.

Model: UN46D6500VFXZA
Symptom: Ghosting image (Double Image)

Solution: Replace the T-Con and LVDS.

Model: LN55C650
Symptom: Colored Vertical lines

Solution: Bring up the “Picture Test”. If the lines appear in the Picture Test, the cause is a bad panel. If the lines do not appear, disconnect all signal sources and check again. If the lines are still in the Picture Test, change the main board. If the lines are gone, then a signal 
source is causing the problem.

Tech troubleshooting – TCON board – Backlight Dimming through TCON board – Deference between TCON and 3D TCON board - Purpose of LED in TCON board

T-CONs Deliver P-DIM (Dimming Signals) to the Inverter
P-DIM (Called PWM-DIM which stands for Pulse Width Modulation Dimming) is a signal from the Main board that is generated by monitoring the Video content’s average brightness level. It is then sent to theBacklight driver IC to control the brightness of the backlights accordingly. The maximum brightness level isestablished by the customer through the Customer’s Menu in the Video selection under Backlights. Thissetting has a bar graph that can be set from 100% down to 0%.
The P-DIM signal will follow the percentile setting proportionately. The range of P-DIM is 3.3V to 0V. Sowhen the bar graph is set for 100% the P-DIM line will be 3.3V and the backlight brightness will be maximum.
Most often the P-DIM line is routed directly from the Main board to the Power Supply, it is routed through thePower Supply directly to the Inverter and then to the Backlight driver IC.
(If the Power Supply has an on-board Inverter, the Driver IC is on the Power Supply itself). However,on some sets, the P-DIM line is routed to the T-CON board.The T-CON then generates a control signal that is then routed to the Inverter and then to the Driver IC.

Here is the T-CON from a 42SL80. The connector in the bottom left goes to the Inverter and carries the P-DIM Control Signals. The P-DIM signal from the Main board is brought in on pin 8 of the left LVDS and is then routed to the large MCM IC. Then it is output through the 8 pin IC on the bottom left to the connector.

Troubleshooting the P-DIM Line when Routed Through the T-CON

When troubleshooting this type of P-DIM routing, you will still use the same procedure. Enter the Customer’s Menu and go to Video, then select Backlights. Place a DC voltage meter on the output from the T-CON CN3or the input to the Inverter CN2. You can check either of the two pins. While adjusting the Backlights from 100% down to 0% the P-DIM lines will vary accordingly from 2.4V at 100% down to 0.67V at 0%.

Pin	Label	Run	Diode Test
1	n/c	n/c	n/c
2	SCAN 1	0.67V>2.4V	Open
3	SCAN 2	0.67V>2.4V	Open
4	Gnd	Gnd	Gnd

Function of the Blue LED on Some T-CON Boards

On some of the LCD T-CONs there is a bright Blue LED that turns on for a brief moment during turn on and then it shuts off. These are only used in set with Florescent Bulbs as the Backlights. As in the example below (from 42LG60), it shows the Blue LED is on the lower right hand side.
The purpose of LD1 is to help excite the Selenium gas in one of the backlight bulbs. This helps the bulb to light when there’s little room light by pre-exciting the gas. With little room light, the gas in the florescent Bulbs tends to lie dormant, (Little movement). This LED help to get the Electrons moving just before the point of firing (turning on).  There is a small hole under LD1. This is how the light goes through the board to get to the Bulbs. (There is a hole in the back metal cover of the panel as well).

Differences between a T-CON and a 3D FRC T-CON

The typical T-CON’s basic responsibilities are to drive the TFT panel and to generate panel voltages.The video input through the LVDS cables is already formatted for usage by the T-CON board.

Typical T-CON

The 3D FRC T-CON basic responsible to; generate panel voltages. When not in 3D it generates the Tru-Motion, Motion Estimated Motion Compensated (MEMC) frames. When in 3D it unpacks 3D frame content. It generates 3D sync which is used by the 3D Shutter glasses. It formats the video for usage by the panel driver circuit and it drives the panel. The video input through the LVDS cables is 24 bit LVDS video.

3D FRC T-CON

Since the 3D FRC T-CON does so much more work than a standard T-CON, it has an additional 12V input via a two wire connector. The voltage is from the same source as a typical TCON board. It comes from the  power supply and switched on/off by the Main board.

SYLVANIA LC220SS2 - EMERSON LC220EM2 - MAGNAVOX 22ME601B - Service mode – Vcom adjustment – Initialization – firmware update

Service mode:
1. Turn the power on.
2. Press [MENU] button to display Setup menu.
3. Select “Features”.
4. Select “Current Software Info”.
5. Press [0], [4], [2], [5], [7], [4] and [INFO] buttons on the remote control unit in this order. The following screen appears.

1. Purity Check Mode
This mode cycles through full-screen displays of red, green, blue, and white to check for non-active pixels.
1. Enter the Service mode.
2. Each time the [7] button on the remote control unit is pressed , the display changes.

3. To cancel or to exit from the Purity Check Mode, press [CH RETURN] or [PREV CH] button.

VCOM Adjustment

1. Operate the unit for more than 60 minutes.
2. Set the color analyzer at the zero point calibration and bring the optical receptor pointing at the center of the LCD-Panel.
Note: The optical receptor must be set perpendicularly to the LCD Panel surface.
3. Enter the Service mode.
4. Press [3] button on the remote control unit.
5. Press [CHANNEL UP/DOWN] buttons on the remote control unit so that the color analyzer value becomes minimum.
6. To cancel or to exit from the VCOM Adjustment, press [CH RETURN] or [PREV CH] button.

The White Balance Adjustment should be performed when replacing the LCD Panel
or Digital Main CBA.
3. White Balance Adjustment
Purpose: To mix red and blue beams correctly for pure white.
Symptom of Misadjustment: White becomes bluish or reddish.

ITEM	SPECIFICATION
Color temperature	x= 0.272 +/-0.002 y= 0.278 +/- 0.002
Input Signal	Internal pattern (40/70% raster)
Measurement point	Screen center
M. EQ.	CA-310 (KONICA MINOLTA Luminance meter) or measuring instrument as good as CA-310.
Aging time	60min. (Retail MODE/100IRE Raster HDMI 1080i@60)
MODE setting of TV	Shipment setting/ Retail MODE
Ambient temperature	25 degreeC ± 5 degreeC

1. Operate the unit for more than 60 minutes.
2. Enter the Service mode.
3. Press [VOLUME DOWN] button three times on the remote control unit to select “Drive setting” mode. “Drive” appears on the screen.
4. Set the color analyzer at the CHROMA mode and zero point calibration. Bring the optical receptor pointing at the center of the LCD-Panel.

Note: The optical receptor must be set perpendicularly to the LCD Panel surface.
5. Press [3] button to select the “HDB” for High Drive Blue adjustment. (“HDB” appears on the screen.)

6. Press [MENU] button. The internal Raster signal appears on the screen. (“Internal (Single)” appears on the upper right of the screen as shown below.)

7. Press [CHANNEL UP/DOWN] buttons to adjust the color temperature becomes 12000 degree K (x= 0.272 / y= 0.278 ±0.002).
8. Press [1] button to select the “HDR” for High Drive Red adjustment (“HDR” appears on the screen.) and press [CHANNEL UP/DOWN] buttons to adjust the color temperature.
9. If necessary, adjust the “HDB” or “HDR” again.
10. Press [6] button to select the “LDB” for Low Drive Blue adjustment (“LDB” appears on the screen.) and press [CHANNEL UP/DOWN] buttons to adjust the color temperature.

11. Press [4] button to select the “LDR” for Low Drive Red adjustment (“LDR” appears on the screen.) and press [CHANNEL UP/DOWN] buttons to adjust the color temperature.
12. If necessary, adjust the “LDB” or “LDR” again.
13. Press [VOLUME DOWN] button to shift to the “Debugging Message” mode.
If there is no message under “[WB]” section, this adjustment completes. If “Drive settings are NG. Retry.” is displayed, repeat above steps from 5. to 12. Then check
“Debugging Message” again. If “Drive settings are NG. Retry.” is displayed, replace the LCD Panel or Digital Main CBA.
14. To cancel or to exit from the White Balance Adjustment, press [CH RETURN] or [PREV CH] button.

INITIALIZE THE LCD TV
The purpose of initialization is to place the set in a new out of box condition. The customer will be prompted to select a language and program channels after the set has been initialized.
To put the program back at the factory-default, initialize the LCD TV using the following procedure.
1. Turn the power on.
2. Enter the service mode.
- To cancel the service mode, press [POWER] button on the remote control unit.
3. Press [FREEZE] button on the remote control unit to initialize the LCD television.
4. "INITIALIZED" will appear in the upper right of the screen. "INITIALIZED" color will change to green from red when initializing is completed.

Firmware Update Procedure

1. Turn the power off and unplug the AC Cord.
2. Insert the USB storage device to the USB port

3. Plug the AC cord in the wall outlet and turn the power on.
4. The update will start and appear on the screen.

5. When the firmware update is completed, Remove the USB storage device from the USB port. Turn the power off and turn the power on again will appear on the screen.

Note:
When the Factory Upgrade is used, after restarting TV, shift to initial screen menu in service mode. "INITIALIZED" will appear on the upper right of the screen. "INITIALIZED" color will change to green from red when initializing is completed.

TCON Board – What is TCON board – What is the Function of TCON board – TCON board Voltages – LVDS Cable Configuration

FUNCTION OF TCON BOARD
The T-CON (TFT Controller) is responsible for;
1. Driving the TFT panel. This is usually accomplished by two LVDS type cables between the T-CON and the panel. The panel cell structure as into Vertical columns and Horizontal rows.
# Horizontal Resolution: On a panel with a resolution of 1920 X 1080 we must have 1920 X 3 columns, because a pixel is comprised on a Red, Green and Blue cell. So there will be 5760 individual cells in rows across the screen. To turn these cells on and off, the panel will use verticaladdress lines or electrodes driven by a small board located inside the panel. In this way we can turnthe colors on and off accordingly to recreate the correct colors required to recreate the image.
# Vertical Resolution: On a panel with a resolution of 1920 X 1080 there will be 1080 horizontal rows of cells running across the panel. These rows are being driven by a small board inside the panel. Byaddressing a particular cell via the vertical columns and turning on a row of cells, only the cells being address by the vertical electrodes will be activated. The number of horizontal rows determine the panels Vertical resolution.
2. TFT: Each cell has is driven by a thin film transistor called (TFT) and a capacitor. When that cells is addressed (turned on) the capacitor will charge and will remain charged until the next refresh cycle.Generally speaking, when the cell has no power applied, it blocks the light from passing through, when it turns on, dependent upon how long it is on, allows more or less light to pass. In this way we can control the brightness level being output by that cell.
3.Panel Voltages: The T-CON is responsible for developing panel voltages. These voltage will vary dependent upon the type of panel utilized. Generally state there will be 4 voltages that are always being delivered to the panel, -5V, 3.3V, 16V and 26V. However, there may be more according to the type of panelbeing used.

Backlights: Since the Liquid crystal panel does not generate any light of its own, there must be a light source behind the panel. This light source is called the “Backlights” called B\L here after. The B\L can be either florescent (EEFL or CCFL) or they can be LED. 

Voltage Source for the T-CON

The T-CON Voltage Source will always be provided from the Main board. However, the Main board does not actually generate the T-CON source voltage. All the Main board does is switch on and off the voltage coming from the Power Supply. The Power Supply generates a 12V supply that is sent to the Main board. When it is time to turn on the T-CON, the Microprocessor will send out a command that turns on the T-CON 12V and this voltage is routed through LVDS cable to the T-CON.

Voltages that the T-CON Generates.

When the T-CON receives the 12V from the Main board, it turns on DC-to-DC converters on the T-CON board to generate several voltages. Some are used on the T-CON board itself (3.3V and 1.0V) and some are sent to the panel’s internal horizontal and vertical driving board. Generally speaking, there are 4 primary voltages sent to the panel. They are -5V, 3.3V, 16V and 26V. It is important to always check for these voltages if you having problems with the T-CON board. But always remember there may be more voltages generated and sent to the panel on different types of panels.

LVDS Cable (Low Voltage Differential Signal)

The picture below shows the LVDS cables routed from the Main board to the T-CON.

About LVDS Cable.

The LVDS (Low Voltage Differential Signal) Cable in a LCD TV is responsible for two primary jobs.
1. VIDEO and TIMING SIGNALS: To deliver video signals that have been processed into a positive and a negative going pair of signals. These pair of signals are sent is groups which equal the resolution characteristics of the panel. As an example if the panel is a HD panel, the differential pair will be 10 lines carrying positive and negative video data. And there will be two line carrying positive and negative clock signals. If the panel is a full HD panel, it will have double the amount of lines.
The positive signals will be designated on the schematic with the suffix of (P or +) and the negative lines will be designated as (N or -). If you take one pair of video signals and look at them on a Oscilloscope, they will be and exact mirror of each other. By using a differential pair, the circuitry can isolate and remove the noise on the line by addition and it can extract the actual signal by subtraction which will double the signal level.
2. T-CON VOLTAGE: The T-CON board needs voltage to operate, the LVDS cable will deliver the T-CON’s operational voltage form Mother board.
If the LVDS cable is suspected of having a problem, most often it can be seen visually. Look for the cable being bent which cause the internal paths to be broken. The cable can be cut, or cracked or physically damaged in some way. The other problem that the LVDS cable can have is the continuity of contacts that are on the side that goes into the connector. This can only be seen by unlocking the cable connector and removing the cable. Then flipping the cable so the contacts points can be seen. See if they are separated from the cable. They could be curled up or even bent over and pressed onto another line causing a short. One other thing to look for is the cable being incorrectly inserted into the connector, (improperly seated).

When the LVDS cable is causing a problem, the symptom can be many. Lines in the picture, portions blocked out, every other line missing, noise pattern on the screen. Missing 12v to the TCON board causing a black or no picture symptom, etc… It can even shut the TV down if the 12V is shorted.

LVDS Cable Connectors

The LVDS cable can use different types of connections to the Main board and to the T-CON.
Below shows some of the types of LVDS cable connections being used in LCD TVs.

CLICK ON THE IMAGE TO ZOOM IN 

LVDS Connector Contents

Pin	Label	Run	Check Diode
1	Gnd	Gnd	Gnd
2	3D_Sync_Out	0.03V	2.34V
3	*V_SYNC	3.33V	1V
4	SDA3_3.3V	3.34V	1.73V
5	SCL3_3.3V	3.34V	1.73V
6	FRC_RESET	3.32V	Open
7	n/c	n/c	n/c
8	3DTV	0V	Open
9	3D DIM	0V	Open
10	3D_DIM_2	0.05V	Open
11	n/c	n/c	n/c
12	RRXA0-	1.17V	1.67V
13	RRXA0+	1.19V	1.67V
14	RRXA1-	1.19V	1.67V
15	RRXA1+	1.17V	1.67V
16	RRXA2-	1.22V	1.67V
17	RRXA2+	1.14V	1.67V
18	Gnd	Gnd	Gnd
19	RRXACK-	1.16V	1.67V
20	RRXACK+	1.20V	1.67V
21	Gnd	Gnd	Gnd
22	RRXA3-	1.20V	1.67V
23	RRXA3+	1.14V	1.67V

Pin	Label	Run	Check  Diode
24	RRXA4-	1.26V	1.67V
25	RRXA4+	1.08V	1.67V
26	Gnd	Gnd	Gnd
27	n/c	n/c	n/c
28	RRXB0-	1.19V	1.67V
29	RRXB0+	1.19V	1.67V
30	RRXB1-	1.19V	1.67V
31	RRXB1+	1.16V	1.67V
32	RRXB2-	1.2V	1.67V
33	RRXB2+	1.14V	1.67V
34	Gnd	Gnd	Gnd
35	RRXBCK-	1.16V	1.67V
36	RRXBCK+	1.2V	1.67V
37	Gnd	Gnd	Gnd
38	RRXB3-	1.22V	1.67V
39	RRXB3+	1.14V	1.67V
40	RRXB4-	1.26V	1.67V
41	RRXB4+	1.09V	1.67V
42-46	Gnd	Gnd	Gnd
47	n/c	n/c	n/c
48-51	PANEL_VCC	11.59V	Open