Sony Bravia 55" Double image / Image Flickering ( CKV - Clock Vertical Signal ) LED Panel Repairing

Double Image fault solution through CKV, CKVB and STVP Signal Cutting.

What is Ckv CKVB STVP in LCD TV?

Pulse-pulse CKV, CKVB, STVP used as pulse “Row driver” or also called “Gate – driver”. …

What is CKV in LED TV?

The CKV signal detection circuit comprises a first LED, a second LED, a first light sensor, a second light sensor and a judging module. A node between the first LED and the second LED is used for receiving CKV signals output by the control panel.

What is pair a signal ?

Pair signals mean after the level shifter section we will get the separate output like CKV 1 , CKVB 1 and STV 1. before entering to Gate Driver IC [ COF ] these three signals are synchronizing each other its called signal paring. depending on COF ic this pair will be increase or decrease. example single COF IC is available in scalar board single pair signal only available (ckv 1,ckvb 1, stv 1)

ckv is a positive pulse and ckvb is a generally negative pulse.

CKV SIGNAL Other Names

COG, Gate driver and Panel Explanation

Panel screens, that use gate circuits embodied in glass screen cell (chip on glass - COG). The procedure has a rate of success of 0-100%, depending on your screen panel. You have to accept that sometimes, even the screen panel will work, a thin line may appear aleatory on screen. Also, sometimes, the screen will not respond to any procedure described here.

A display device includes multiple pairs of field generating electrodes and an electrooptical active layer interposed there between. Generally, one of the pair of field generating electrodes is connected to a switching element to receive an electric signal and the electro-optical active layer converts electric signal into an optical signal to display images. The display device typically includes a gate driver and a data driver. The gate driver applies to a gate line a gate signal that turns a pixel on and off, and the data driver converts image data into a data voltages and then applies the converted data voltage to a data line. The gate signals are are processed by the scan driver circuits and amplified by the level shifter to analog signals, which are outputted as the gate pulses for scanning the display panel.

Gate driving circuits can be mounted - (TCP) tape carrier package or printed on glass - (COG) chip on glass. On Samsung panels, gate driving circuits were replaced since 2008-2009 with gate drivers on glass mounted transistors, using ASG technology (Amorphous Silicon Gate).

Each gate line has a block circuit glass mounted transistors called SR, made using ASG technology. The gate driver receives clock signals CKV and CKVB and the start signal STVP, and sequentially apply on voltages to gate lines.

The display area 300 is represented by the resistor Rp and the capacitor Cp. As show below, the gate lines G1-Gn, and the liquid crystal capacitor CIc and storage capacitor Cst , respectively have the resistance and capacitance, and the sum thereof is represented by one resistor Rp and one capacitor Cp.

The gate voltage output from each line block SR1-SRn is analog transmitted through the gate line corresponding.

The SR blocks are connected between, with glass printed connections, and when a component of one SR block faults, owing to the fact that is on glass, the repair is impossible.

However, with some trickery made on command signals of gate drivers blocks, you can partially or totally repair the faults. CKV and phase opposition CKVB signal, and start STVP signal, are synchronizing the gate outputs to screen lines.

For a small screen, we will have only one set of signals: CKV, CKVB and STVP For a bigger screen, we will have 2 gate drivers blocks and 2 sets of signals, CKV1, CKVB1, STVP1 and CKV2, CKVB2, STVP2, each of this signals sets will command a gate driver on down or upper side of the screen.

The fault can be visible on all screen, half of screen, so we need to cut in both signals sets, or one by one, depending on each situation. On large screen panels, starting with 32 inch, there are gate drivers on both sides of the screen, and we can have 2,3 or 4 sets of signals.

In this case, the command of 4 blocks gate drivers (CKV1.....CKV4, etc) are made in various ways, one way it is as below: -first gate signal will command upper side of screen odd lines, second gate signal - lower side of screen odd lines, third gate signal will command upper side of screen even lines, fourth gate signal lower side of screen even lines.

A fault screen will display in many ways: -

Doubled image on all screen, on vertical, or image stop.
Half of screen, upper or lower, doubled or static image, the other half will be correct displayed
On whole screen are horizontal lines where image is reversed or static.
a part of the screen is darker, with lines
vertical flickering image on all screen or upper or lower half of the screen
in an area of the screen, the image have lines on it.
on area where image is not right, can also to have a certain color or fail of color.

REPAIRING SCREENS BY DISCONNECTING GATE DRIVERS SIGNALS.

The generating circuit for gate drivers, called LEVEL SHIFTER or SCAN DRIVER, can be mounted on T-CON drivers, on PWB (printed wire board) connected to screen, or in glass screen.

When level shifter is in glass cell, you cannot disconnect it, but you can try to disconnect the input signal – CPV, STV and OE.

This signals will go on both sides of the screen, thru left and right PWB, you can disconnect one side first, check if any improvement, and if not,

disconnect other side and re-connect first one. First of all you have to check where is the LEVER SHIFTER IC, by finding check points CKV CKVB and STVP.

Usually the LEVER SHIFTER is on TCON board or on T-CON PWB attached to the screen glass cell.

How To Cut LCD/LED Panel CKV and CKVB Lines

I will show you all the steps in detail with Full HD Images. So please do this work at your own risk. I will not be responsible for any damage during the operation. So do that everything at your responsibility.

If you have not the advance knowledge about LCD/LED Panels then it is not recommended for you to do. All the information that is provided here is the educational purpose.

Now you must be aware of this type of fault. This fault comes when rows-driver circuits damaged that exists within the panel. This fault can be solved by cutting some lines called CKV and CKVB and more.

First, you should know what problem will face when you have this fault in your Screen Panel. These are some problems.

You will see the colour of the image will change to magenta or other.
Image may be shown double and vertical or image rolling vertically

Please keep in mind before cutting the lines.

First, you have to understand what line should be cut.
Use a new blade or knife to cut You should take a photograph before cutting
You should use a magnifying glass and full white lighting
Cut in the way that can be reversed, so that you can easily reconnect lines
Which line should be terminated? We must try to play first chancy

Line Cutting Steps

You have to find the exact location of the first left line and right line to cut it, that Line 2 STVP, VSS, CKV1, CKV2 CKVB1, CKVB2 and then each given a sign.

Use the meter to locate each track, because of test point generally only one lane only.
The tip of the probe is a connection piece of a point to facilitate the measurement due to line 2 to be measured sized soft.
If you have found the Line 2, then scraped before the track is cut out so that it’s copper look.
This is useful if it later turns out one piece, so it is an easy path connected by means of solder given the track.

ByPass

Cut the Line that is located near the track entrance panel The direction of the blade should not be perpendicular to the path of the cut but made a slight angle.
Please Remember, Use a new blade, in order to track pieces as small as possible.
It is useful to make it easier if you have to connect the line again Cut the lines CKV 1 and 2 first and then CKVB1 and 2

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