Sony KDL22EX308, KDL32EX308 manual Tcon Troubleshooting Introduction, LCD Panel Basics

Chapter 4 – Appendix

TCON Troubleshooting

Introduction

Beginning in the fall of 2008, Sony announced the availability of limited TCON replacement boards to service LCD panels beginning with certain models going back to 2006. For many years technicians have been asking about the availability of these components. In the relatively small percentage of units that experienced a failure of the TCON board, replacement of the entire LCD panel was mandatory. This is not only costly from a warranty standpoint but it also makes it near impossible to justify an out-of-warranty repair since the replacement LCD panel can easily cost 2/3 or more of the price of the entire television.

The reason why TCON assemblies have not been available in the past was due to the large amount of correction data stored within NVM data points located on the board. Tolerance issues during the manufacture of the LCD panels required white balance, gamma, and uniformity corrections to compensate for these inherent production issues. There are other items for correct panel operation but the above mentioned items are the most critical.

Over the years, panel tolerances have improved dramatically and variances in uniformity have been reduced to the point where a TCON loaded with average data results in a satisfactory picture when installed as a replacement on a panel. Most Sony television models also have white balance data located on the video process board. Although the TCON is loaded with data to properly white balance the panel, the ability to adjust white balance from the B boards is present to compensate for shifts in white balancing due to panel aging and this mainly involves color balance shifting of the fluorescent backlight lamps which tend to shift towards the magenta spectrum as they age.

The main issue with previous LCD panel designs was the uniformity

adjustment data. Due to variances across the LCD panel it was impossible to achieve even white balance across the screen. For this reason, small zones across and down the LCD panel required individual white balance compensation. Without this correction the picture would have “blotches” of different color in sections of the screen. Better tolerances during manufacturing have reduced the reliance on this uniformity data and allows for the replacement of TCON boards with satisfactory results.

As mentioned in the beginning, not all LCD panels will have a TCON board available. This will mainly be determined by availability of components from the LCD panel vendor along with decisions by Sony based on sales quantity and failure history of the TCON assemblies. Most technicians have experienced the use of the LCD panel replacement manual. This manual was created to properly identify the type of LCD panel installed in a unit based on its serial number since some units changed to a different type of LCD panel during the manufacturing production. The plan is to use this document to also provide TCON information and whether one is available and, if available, which TCON is the proper replacement part for that particular panel.

LCD Panel Basics

LCD panels have steadily evolved over the last several years. New designs of the physical structure of the LCD crystals have greatly improved the contrast ratio and viewing angle. Quicker response times and increased refresh rates have helped to reduce the motion “smear” associated with LCD displays. Backlighting design has also aided in producing a picture with color temperatures to make the images as true as possible. With all these design improvements, one aspect of the LCD panel remains relatively the same: Processing of the video signal.

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