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by Slavic Marian ([email protected])

The procedure described in this file, will help you repair a Samsung 2008-2013
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. In this file, I will refer only on repairing gate problems of
fault Samsung cell screen panels.

A display device includes multiple pairs of field generating electrodes and an electro-
optical 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.
We are interested only in gate signal circuit, this is the one that faults and need
to be fixed.

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 G1-Gn.
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

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

However, with some trickery made on command signals of
gate drivers blocks, you can partially or totally repair the
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
-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 a 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

2.1) 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.
2.2) When level shifter is in glass cell, you cannot disconnect it, but you can try
to disconnect the input signal