KDL-46EX400 – Sony LCD TV – T Con board faults – Main digital board faults – Troubleshooting

KDL-32EX301 KDL-32EX500 KDL-46EX400 KDL-32EX400 KDL-40EX500 KDL-46EX500 KDL-40EX400 KDL-40EX501 KDL-46EX501 KDL-40EX401 - Sony LCD TV - Troubleshooting

Video Symptoms and Troubleshooting

All video processing is performed by IC400 (MT5388) on the A-Board.  The RF input is first processed by the RF Tuner and is then applied to IC400. Both the ATSC and NTSC signal are processed by IC400. All four HDMI inputs are first applied to a HDMI switch circuit (IC6601). The switch circuit applies the selected input to IC400. IC6601 also contains the EDID (Extended Display Identification Data), which is part of the HDMI handshake process.
All other inputs (Composite, Component, PC, and USB) are connected directly to IC400 inputs.
The USER, White Balance, and Gamma data is stored in IC4302.  Both the USER Menu and Service Mode screen are generated by, and output from IC400.

1) Confirm the TV has the most recent Software Version installed.  Go to the User Menu for the present TV software revision and the ASC web site for the most recent software version.

2) Before proceeding with the following video troubleshooting procedures it is assumed that the TV is turning on with the Green Power-LED illuminated, Backlight is illuminated (brightened raster), and the Audio is present.

When a video problem occurs you will experience one of the two following symptoms.

Input Status

• Missing or Distorted Video (Individual Inputs)

• Missing or Distorted Video (All Inputs)

Video Anomaly:

• Poor Detail

• Moving Video Distortion (e.g. Bars)

• Static H/V Lines (Any Color)

• Static Missing Pixels (Any Color)

• Static Bars (Solid Black or White, Transparent Color)

• White Balance

• Gamma

The main objective when troubleshooting one of the previously listed symptoms is to determine if the defect exists in the following sections of the TV system.

• LCD Panel Assembly

• TCON/HFR Board

• A-Board

Missing or Distorted Video (Individual Inputs)
The primary objective is to locate the defective component through activating each individual video input and checking for any abnormal symptoms on the screen. If the video distortion appears only in one or two video inputs then the next step is to eliminate the possibility of a defective or improperly connected external device such as, a STB, DVR or DVD player. The quickest way to troubleshooting the external devices is to swap the suspect device with a known good device at the input in question.  If the external device or connections are defective then the TV is okay and the external device and connections need to be serviced. If the external devices and their connections are okay, then the next step is to troubleshoot the problem by accessing and displaying each video input.  The rationale behind this troubleshooting method is that each of these video inputs takes an altogether or somewhat different path through the video processing system. This fact enables you to determine the defect, in some cases, down to the component level, and in almost all cases, down to at least the board level. For example, if the distortion appears in
a HDMI input but not in any other inputs (e.g. composite or component) then most likely the HDMI Switcher (IC6601) is causing the distortion.  The reason for this conclusion is because the HDMI signals are the only signals to pass through IC6601 before being applied to IC400. All other input signals bypass IC6601. The composite and component signals go directly to the video processor IC400.  Although all the individual input circuits are located on a single board (ABoard), the previously described troubleshooting procedure can still serve as a reliable confirmation of a defective component on the A-Board before replacing the board.
The same deductive reasoning can be applied when troubleshooting  video defects using the other video inputs. This method simply involves knowing the path the input signal must take through the video processing system to reach the display. With this knowledge you can effectively divide the video system into distinct areas, and therefore, isolate the defect.

Missing Video (All Inputs)
If the video is completely missing you will first use the User Menu (OnScreen-Display - OSD) in an attempt to isolate the defect to the A-Board or the TCON/HFR Board.
If the OSD can be displayed then the TCON/HFR Board is okay, and you can safely assume the defect exists on the A-Board. However, if the OSD cannot be displayed you need to do further troubleshooting because either IC400 on the A-Board is not sending the OSD or the TCON/HFR Board is not able to process the OSD and display it on the LCD Panel.  If the OSD cannot be displayed then the LVDS signal levels must be checked to reliably determine whether the A-Board or the TCON/HFR Board is defective.

1) Check for USER Menu OSD Display
a) USER Menu Displays. Replace A-Board
b) USER Menu Does Not Display. Go to Step 2

2) Check for TCON 12V at CN4152/pins 4 - 10 & CN6151/pin 2
a) No 12V. Check connections between A-Board & Panel
b) 12V Present. Go to Step 3
3) Check LVDS Cable Video Signal Levels at CN4152
a) LVDS Video Signal(s) Low or Missing. Replace A-Board
b) LVDS Video Signal(s) Okay. Replace TCON/HFR Board
Skewing LVDS Connector Troubleshooting Method
It may be difficult or impossible to check the LVDS signal while in the field.  Therefore, a quick and somewhat reliable method of checking the TCON/HFR operation is to skew the LVDS connector out of the its mount at the TCON/HFR Board. When performing this method it is important to keep the 12V end of the connector connected while dislodging the LVDS video connections. Therefore, find the 12V using a voltmeter. The 12V is usually
on one end of the connector (usually left-side on bottom mount or top on side mount connect).  When skewing the connector if color flashing occurs on the screen then the TCON/HFR Board is most likely okay and the A-Board is defective. If the is no video reaction on the screen while skewing the connector then the TCON/HFR Board is defective.

Unique TCON/HFR Board Effects

• 2” Vertical Transparent Colored Bar- The bar will be approximately 2" because this is the area that is controlled by a single drive IC that is located across the top of the LCD Panel assembly.

• Video Timing - The Video Timing distortion may appear as a double image or ghosting type distortion.

• Loss of Half Screen Video - Half the screen will have live video and the other half will be a white raster.

• Half or Full Screen Video Distortion - In this case, the key distinguishing factor is the presence of undistorted video behind the color distortion. The distortion is basically an overlay (transparent color half-screen or bar) in front of the good video coming from the A-Board.

• White or Colored Blooming - The bloomings may come down from the top of the screen and vary in size.

• GAMMA Irregularity - A GAMMA distortion will appear as a overall brightness problem or a localized area color distortion.

Distortions and anomalies where fixed by replacing the TCON/HFR Board.

Distorted Video (All Inputs)

The following paragraphs describe the unique and common effects the LCD Panel Assembly, TCON/HFR Board, and A-Board have on the displayed video concerning possible distortions. Knowing how each component affects the displayed video can be very helpful in troubleshooting a distorted video condition.

NOTES: Reference Appendix for picture examples of unique distortions for the LCD Panel, TCON/HFR Board, and the A-Board

WIDE Mode Button (Aspect Ratio) Troubleshooting Method

A quick test tThe aspect ratio can be easily changed using the “WIDE” key on the remote controller. If the distortion follows the video then the A-Board is causing the distortion. If the distortion remains stationary after changing the aspect ratio then the LCD Panel assembly is causing the distortion.o determine if the A-Board, TCON/HFR, or LCD Panel is causing the distortion is to change the panel aspect ratio (or picture size).

Unique Main Video Board (A-Board) or LVDS Cable Effects

A video distortion that has soft edges and/or is moving through the video is most likely caused by a defect in the video processing circuitry. All video processing circuitry is located on the A-Board. Therefore, replace the ABoard if the video distortion has soft edges and/or is moving through the video on the screen. Macro-Blocking (digital picture breakup) is a good example of this type of distortion. Be careful though, macro-blocking can also be caused by a weak RF signal when the TV is in the tuner mode.

• Poor Picture Detail - Loss of overall picture detail. A loss of information on the LVDS lines from IC400 will cause poor overall picture detail.

• Abnormal Picture Size or Geometry- The video signal scaler circuit is located on the main video board A-Board. Therefore, if either the picture size or geometry is abnormal the A-Board is defective. Only the A-Board can cause such a distortion.

• Color Distortion - A color distortion can be caused by a defective IC400 or LVDS cable. The individual color signals are spread out over the LVDS twist pair wires. For example, the Red signal may be broken up into three components and sent over three different LVDS twisted pairs. Therefore, this distortion will display as a poor reproduction of a particular color not an overall loss of one color. Use a Red, Green, and Blue raster generator to confirm a poor reproduction of a single color.

• Loss of a Single Color - A loss of a single color can only be caused by a defective MT5388 (IC400). Use a Red, Green, and Blue raster generator to confirm a complete loss of a single color.

• RF Signal Distortion - A weak video signal from the antenna or cable connection can cause RF video distortions. The signal strength of the Digital Signals can be checked in the USER menu. Go to the Product Support and Signal Diagnostic item to check signal strength and errors. NOTE: This is only for digital channels. No information will display for analog channels. The SNR should be in the range of 25db to 30db and there should be zero Errors.

Distortions and anomalies where fixed by replacing the Video Board.

LCD  Display Panel defects

Unique LCD Panel Assembly Effects
• Line(s) of Pixels (Fixed Position) - Poor physical connection (or bonding) between the LCD Panel and the flex cables will cause a loss of line(s) of pixels. The pixel drive lines can be open (no drive) or shorted (drive all the time). Depending on the type of failure the line(s) or pixel(s) will be black, white, or colored (red, green, or blue). These lines and pixels will also be very sharp in detail.
• Random Line(s) of Pixels (Random Movement) – The TCON board controls the charging and timing of the pixels.  If the TCON Board is partially defective random lines and/or pixels will be seen flashing across the screen. These lines and pixels will be very sharp in detail, like a specific line of pixels are randomly turned off and on.

• 2” Vertical Solid White or Black Bar- The bar will be approximately 2" because this is the area that is controlled by a single drive IC that is located across the top of the LCD Panel assembly.
• Horizontal Bar- Any horizontal bar of any color will be caused by a defective LCD Panel assembly
Common Main Video Board (A-Board) and LCD Panel Assembly Effects
• White Balance (WB) Irregularity - A WB irregularity will show up as an overall poor reproduction of white. A white raster can be used to determine if a WB or gamma irregularity has occurred. WB will cover the complete picture, where as, gamma will be in specific zones or specific color areas in the picture. WB adjustment data is stored in the EEPROM IC4302 on the A-Board. The WB data stored in IC4302 is set to the middle value of the data span. The TCON/HFR Board also contains WB data, which is specifically set for the associated LCD Panel.
• GAMMA Irregularity - Gamma Correction affects the overall picture brightness level and individual color (RGB) brightness levels. Gamma adjustment data is stored in the EEPROM IC4702 The TCON/HFR Board also contains GAMMA data, which is specifically set for the associated LCD Panel.  The data may become corrupted causing irregular gamma adjustment. Therefore, a gamma distortion can show up as a color brightness irregularity in specific zones or specific color areas in the picture, as well as an irregularity in overall picture brightness