Picture defects and causes of LCD TVs. Main board fault – T Con board fault.
The reference T’Con here is for LG 32 inch LCD TV. But, the picture defects can be taken as a reference to LCD TVs of all brands, irrespective of its screen size.
Assy
board plate Defects
Horizontal
block
Vertical
line block
Bright
and Dark Spot
Back-light
defects
Dark
Spot Model The ones of LED
Cause:
LED does not light in.
Horizontal Stain Lamp Models (LCD)
Cause: Burning Lamp mead
Impurity
PCB / T-CON Defects
Abnormal image
NO
IMAGE
Backlight
lights up more does not generate image
T-Con
measurement points
Before
changing a module, check that the voltages of the T-Con board are correct.
If
one of them is changed, check to be sure that the flat cable that goes to the
panel is released.
Check
if it is normal if this does not occur and a defect.
Mounting
the connector (A) 30 Pins in the Arrow Pin (1)
1-12V
enters the Fuse pins 1 to 4 of the Connector (A).
2-
The same is done with the GND, Pins 5 to 8 of connector (A) that are connected in
short.
3-
Only Pin 30, connector (A) enters the voltage of 3.3V
Mounting the connector (B) - 51 pins on the Pin arrow (1)
1- See that 12V power supply is connected directly to the Fuse pins 48 to 51 of connector (B) that are shorted.
2. The same is done with the GND, connected in the pins 45 to 46 of the connector (B) Which are short-circuited.
3- Only Pin 44, of connector (B) enters the voltage of 3.3V
4- You can put a switch to turn the source on and off
Click on the pictures to magnify
LCD monitors can suffer from stuck pixels, broken pixels, and residual image problems that can be irritating to have on your screen. Here are some approaches to fixing these problems if they occur.Unlike older cathode ray tube (CRT) displays that scan an electron beam over a phosphor screen to create light, LCD displays are composed of a fixed grid of tricolor pixels that change transparency based on a range of voltage levels provided by the monitor's controller. Without a voltage the pixel is opaque and blocks the screen's backlight from transferring through it, and when a full voltage is applied then the pixel allows full transmittance of the backlight. When this is done over the entire pixel grid in patterns, then you see those patterns on the screen.
At a very basic level, the way pixels work is a voltage change alters the pixel to allow more or less light through. When there is no voltage, no light is let through (darker), and when the voltage is at its maximum level then 100 percent of the light is allowed to pass through (brighter). By supplying intermediate voltages the computer adjusts the pixel's transmittance levels for its three color components, to display various combined colors and intensities.
This pixel-based setup for LCD monitors provides many advantages over CRT displays, but does have potential drawbacks arising from the fact that the image is dependent on millions of independent electrical components as opposed to a single scanning beam, so if faults occur in these components then the display output can be affected. The resulting problems include stuck or dead pixels, as well as a residual image effect.
Fixing stuck pixels
One of the more common problems with LCD displays is the potential for stuck or broken pixels, where the pixel either does not receive a voltage and remains black, or does not respond to voltage changes and stays at a set luminance level. Sometimes this can happen for individual pixels, suggesting a problem with the pixel itself, or it can happen to groups of pixels, suggesting the possibility of problems with the display's controller or a defect in a portion of the pixel grid.
At a very basic level, the way pixels work is a voltage change alters the pixel to allow more or less light through. When there is no voltage, no light is let through (darker), and when the voltage is at its maximum level then 100 percent of the light is allowed to pass through (brighter). By supplying intermediate voltages the computer adjusts the pixel's transmittance levels for its three color components, to display various combined colors and intensities.
This pixel-based setup for LCD monitors provides many advantages over CRT displays, but does have potential drawbacks arising from the fact that the image is dependent on millions of independent electrical components as opposed to a single scanning beam, so if faults occur in these components then the display output can be affected. The resulting problems include stuck or dead pixels, as well as a residual image effect.
Fixing stuck pixels
One of the more common problems with LCD displays is the potential for stuck or broken pixels, where the pixel either does not receive a voltage and remains black, or does not respond to voltage changes and stays at a set luminance level. Sometimes this can happen for individual pixels, suggesting a problem with the pixel itself, or it can happen to groups of pixels, suggesting the possibility of problems with the display's controller or a defect in a portion of the pixel grid.
Fixing LCD residual images
LCD monitors can also be affected by another problem called "transient persistence" that is reminiscent of CRT burn-in. Classic burn-in would happen because the phosphor coating on the screen would get depleted by the persistent bombardment of electrons from the CRT, resulting in the inability of those sections of the display to convert the electron beam to visible light. This meant that if you kept a specific pattern showing on the screen then over time it could become a permanent residual image on the display that would show even when the display was turned off. This was a reason why screensavers were developed--to keep the wear on the screen's phosphor coating as even as possible.
The physical burn-in of displays is no longer an issue now that LCD displays have taken over, but while transient image persistence is not a physical burn of the device, it is an alteration of the pixel response to voltage changes (usually temporary) that prevents pixels from getting as bright as others on the screen.
Similar to CRT burn-in, LCD image persistence generally happens after you have displayed a pattern of intense colors on screen; however, unlike CRT burn-in, LCD persistence can sometimes set in after only a few hours of displaying the image, as opposed to the weeks or even months that it can take for burn to set in on a CRT monitor. Additionally, unlike CRT burn-in, image persistence can often be reversed.
What happens with LCD monitors is the affected pixels have lost their ability to respond to the full range of voltages that the display gives them, resulting in a limited range of colors that can be output. This can happen if the pixel is acting like a capacitor and is retaining a residual charge, or if it is not able to reach the level of luminance that is desired when given a specific voltage. Either way, the pixel is not able to reach its full range of possible intensities.
Unlike stuck or dead pixels that may benefit from having the monitor turned on and off rapidly to produce rapid voltage changes, image persistence will benefit from a lengthy stretching of the pixel's range. Therefore, instead of using tools like JScreenFix to run random patterns over the affected screen area, you might instead place a pure white window (such as an empty TextEdit window, or what you get using the "White" option in the LCD Repair tool listed above) over the affected area for a few hours or even a few days if necessary. Doing this will force those pixels to be fully on, and over time their intensities may increase to be the same as the surrounding pixels.
Likewise, try turning off the pixels fully by shutting down the display for a long period of time or placing a pure black texture over the affected area (see the LCD Repair tool listed above for this option as well). This will turn the pixels completely off and allow residual voltage in them to drain slowly over time.
Beyond pixels
So far we have discussed pixel-based problems with LCD displays, but the system's backlight can also suffer some common problems that include the backlight randomly blinking off, not turning on, or only illuminating part of the screen.
The defective LCD TV may have the following common symptoms:
Symptom: No picture on screen but LCD TV still has sound.
Solutions: The problem is cause by defective inverter. Replacing ivnerter will solve hte problem.
Symptom: Screen flash on and off between 1/2 to a few seconds, but power indicate light stays on and TV still has sound.
Solutions: The problem is cause by defective inverter.
Symptom: Blue Screen but no picture
Solutions: The problem is cause by defective Main Board(AD Board). In some cases, this problem may cause by the defective Screen Controller board. Thsi board is mounting on teh back of LCD TV Screen.
Symptom: Power light stays on but no display and sound
Solutions: The problem is cause by defective Main Board(AD Board) or Power supply board.
Symptom: No Power or Power indicate light does not lits
Solutions: The problem could cause either by defective Power supply board or defective Main Board(AD Board).
Symptom: Screen is half dim and half bright
Solutions: The problem is cause by defective LCD Panel.It needs to be replace.
Symptom: No picture on screen but LCD TV still has sound.
Solutions: The problem is cause by defective inverter. Replacing ivnerter will solve hte problem.
Symptom: Screen flash on and off between 1/2 to a few seconds, but power indicate light stays on and TV still has sound.
Solutions: The problem is cause by defective inverter.
Symptom: Blue Screen but no picture
Solutions: The problem is cause by defective Main Board(AD Board). In some cases, this problem may cause by the defective Screen Controller board. Thsi board is mounting on teh back of LCD TV Screen.
Symptom: Power light stays on but no display and sound
Solutions: The problem is cause by defective Main Board(AD Board) or Power supply board.
Symptom: No Power or Power indicate light does not lits
Solutions: The problem could cause either by defective Power supply board or defective Main Board(AD Board).
Symptom: Screen is half dim and half bright
Solutions: The problem is cause by defective LCD Panel.It needs to be replace.
