LCD TV Description - Help with DIY LCD TV Repair Diagnosis - Common Symtoms Problems
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While no two LCD TVs look the exact same both inside and out. There are some fundamental pieces needed to make an LCD TV. Lets remove the back cover and bezel and take a look inside of a few. With the cover removed you can see that an LCD TV is basically a lightbox with LCD Display on the front and printed circuit boards on the back. The metal lightbox and screen make up the LCD display assembly or panel. And the area where the circuit boards are arranged on the backside of the display assembly is typically called the chassis. Searchable part numbers and serial numbers for the LCD display assembly can be found on the labels on the chassis side.
The LCD display screen is a thin sheet of thin film transistor or TFT glass. Small driver boards are connected to the screen via copper and gold ribbon cables. Unlike most other ribbon cables found in LCD TVS these are permanently adhered to the screen and driver boards with an industrial adhesive. Which makes replacing the screen, driver boards or ribbon cables impossible without changing the entire assembly.
Behind the LCD screen are several layers of plastic polarizers and diffusers. These help focus and balance the light across the screen. Replacement of these items are not commonly needed and are typically not available from vendors.
LCD TVs utilize Cold Cathode Fluorescent Lamps or CCFLs for a light source. The number of CCFLs arranged inside of the display assembly vary by size and manufacturer. And sometimes require soldering tools and experience in order to replace. ShopJimmy doesn't typically stock CCFLs but if you are ever in need of any give us a call and we will see if we can help you out.
The final item found inside of the display assembly is a reflective surface to intensify the amount of light hitting the polarizer and diffusers. This is typically a sheet of metal foil or white plastic.
Let's flip over the LCD assembly and take a look at the chassis. This is where the fundamental circuit boards are mounted.
While LCD TV circuit boards vary in appearance and location. An LCD TV needs the following items in order to function.
The power supply takes in and distributes power throughout the TV. This board is either directly connected to your AC power cord or is connected to the AC adapter.
The main board typically manages your accessory inputs and outputs and houses the TV tuner.
The backlight inverter or set of inverters drive the CCFLs inside of the display assembly. The backlight inverter is typically located on the left hand side of the chassis. If there are multiple backlight inverters in the chassis, the master will typically be the inverter on the left and the slave will be the inverter on the right.
The timing control or T-Con board is connected to the main board via the LVDS cable, and connects to the LCD display via ribbon cables that protrude through the top or bottom edge of the chassis.
Backlight inverters and T-Con boards are typically included with the LCD assembly, and may be covered by a vented piece metal or plastic.
The LVDS cable connects the main board to the T-Con board. The flat 12-25 pin connector on the T-Con side of the LVDS cable can break while handling and is difficult to repair. Replacement LVDS cables can be found by using your TVs model and chassis information as search terms on shopjimmy.com.
Sometimes the power supply and backlight inverter are combined onto a single circuit board. These are called LCD Integrated Power Supplies or LIPS boards. And in some cases typically with Emerson and Sylvania, the components of the power supply, main board, and backlight inverter are split between two circuit boards. These are sometimes called MPS and MUT boards.
Top Common LCD TV Problems:
• No Backlight
• Lines on TV Screen
• Solarization, Inverted LCD Display, Negative Picture
• No Power, No Standby Light, Bad Power Supply Unit
• Power Cycles Off, Red Standby Light Blinks
• Bad Capacitors (Blown Caps)
• Vertical Lines, Vertical Bars
• Bad Main Board
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