Samsung UE55KS7000 and UE49KS7090 main board protection mechanism

[kevinallein]

I have two Samsung KS series TVs (UE55KS7000 and UE49KS7090). Both have some panel issues. I would like to diagnose those for panel repair.
Those main boards have the TCON integrated.
In many Internet posts and Youtube videos those people show, that they separate the left or right cable from the TCON / main board to the Panel to diagnose, whether the problem is on the right or left side of the panel.
However on that KS series, as soon as I disconnect one side or even just disconnect one of the driver boards of the panel itself (left and right side have two driver boards each), the TV will not turn on.
I assume this is some internal diagnostics to protect the TV. Does anyone know, what is measured here and whether that protection can by bypassed ?

[Diah]

Originally Posted by kevinallein

I have two Samsung KS series TVs (UE55KS7000 and UE49KS7090). Both have some panel issues. I would like to diagnose those for panel repair.
Those main boards have the TCON integrated.
In many Internet posts and Youtube videos those people show, that they separate the left or right cable from the TCON / main board to the Panel to diagnose, whether the problem is on the right or left side of the panel.
However on that KS series, as soon as I disconnect one side or even just disconnect one of the driver boards of the panel itself (left and right side have two driver boards each), the TV will not turn on.
I assume this is some internal diagnostics to protect the TV. Does anyone know, what is measured here and whether that protection can by bypassed ?

any tv with out external T-CON this LVDS disconect one side will not work.

if you remove the U ribbon on one side of the panel boards TV should remain On with 3/4 screen view.

it would be better if you show us photos of the issue and panel boards over here.

[neilc6]

I had a Samsung with no separate tcon that didn't turn on. Owner then indicated the screen had been hit on the edge of the screen. I cut off the flex to the outer section and the TV turned on so it does appear there is some sort of protection mode in these models.

[Diah]

well i cant call it protection. its just ask and answer ( i am ready ) command from the panel to the CPU .. if we hide the damaged area on the panel will trick the panel to send (i am ready) to CPU so the next start step script will be in place.

[kevinallein]

Here is a picture of the UE49KS7090.
- With all cables connected it starts with bad picture.
- If I disconnect any of the Flex cables, either the ones from the main board to left or right or the connecting cables between the two subassemblies in left or right the TV will not start. I am missing the negative voltages VOFF, so I wanted to check, whether the problem is on the left or right side.

Funny enough, on the UE55KS7000, which uses the same main board, the leftmost subassembly is disconnected and the TV works with 3/4 of the screen fine.

I am trying to find out the pinning, however I struggle to associate the signal labels with the test points. Please see pics attached.
In the Net I have found a service manual for the KU series, but it seems the pinning between main board and panel is different from the KS series.

Any hints ?

[Diah]

same issue on this threat

show us the 8pin chips on the panel left side ( when you looking from the back side with out cover.. write it lable

[kevinallein]

By the way, just saw this Youtube Video with a different older model, where one Samsung board with integrated TCON allows to disconnect a cable and still starts:

https://www.youtube.com/watch?v=E6gkuTP7Lt0&t=900s

[kevinallein]

The only chip on that panel assembly is a 3V 64M-BIT SERIAL FLASH MEMORY WITH
DUAL/QUAD SPI & QPI

[Diah]

the threat i linked to you was it boot complete when he disconnected both as he said.

[Diah]

Originally Posted by kevinallein

The only chip on that panel assembly is a 3V 64M-BIT SERIAL FLASH MEMORY WITH
DUAL/QUAD SPI & QPI

the lable of it ?... this one which SPI and I/O which comunicated with CPU

[kevinallein]

Here is the picture of the SPI Flash

[kevinallein]

Originally Posted by Diah

the threat i linked to you was it boot complete when he disconnected both as he said.

I just double checked, with both Flexcables between main board and Panel disconnected, my TV is in the reboot loop.
So I guess KS series and NU series behave differently here.

[Diah]

Originally Posted by kevinallein

I just double checked, with both Flexcables between main board and Panel disconnected, my TV is in the reboot loop.
So I guess KS series and NU series behave differently here.

your issue need to narrow it. take out the cable between PCB and MB then turn on see if the backlight come one and messure vcc on the socket if all group are same level of V. or if one go up and then down even the light come on. if this done and all correct then i would consider to put the 55 MB on 49 to see if it boots as u did on 55 3/4 screen view

[MixyourMind]

Hello,
Typical panel problem, drivers or smd short. 90% the right side. Measure VDD and VGL on T Con.

[kevinallein]

Originally Posted by MixyourMind

Hello,
Typical panel problem, drivers or smd short. 90% the right side. Measure VDD and VGL on T Con.

The negative voltages of -7.5 V and -11 V are missing, the positive ones of 8.5 and 17 V are good.
When you write "right side", is that from the perspective of the TV open and looked from behind or from the front of the TV (as you would normally watch it) ?
The driver boards are actually labeled "left" and "right" and they are as seen from the back.

[kevinallein]

Can someone please help ? On the scalar board of the panel I see those two labels "VOFFE_-11V" and "VSS_-7.6V" and I thought, those could be observed on the two test points I marked with a white arrow.
However I found out, that those two test point connect to "VCOM2_CELL" and "VCOM3_CELL".
So where can I see the negative voltages ?

[lotas]

Control points are usually marked with round heels, like this:

[kevinallein]

But where would those test points in this pic be then ?

[lotas]

They can be disguised as here:

[kevinallein]

Originally Posted by lotas

They can be disguised as here:

So I need to scratch off the protection paint before ?