Sony 50" TV KDL-50W800B LED display issue

[Shock]

Taking a look at this LED TV.

Fault:
Responds to power on from standby.
Remote and audio seems to work.
When turning on with remote a thick horizontal white bar appears.
After a few seconds this bar seems to compress and then blue vertical lines are seen.

Troubleshooting:
Cleaned and reseated the connectors and boards.
Inspected the connectors on cables, they look in good condition.

No change, wondering where to start on this one.

Repair and service manuals.
https://www.manualslib.com/download/1087617/Sony-Kdl-50w800b.html
https://www.manualslib.com/download/1258726/Sony-Kdl-32w700b.html

[HecticZA]

Not the same, but I wonder if this process might be of use for you?

https://youtu.be/u1aA2TIKs4M

Sent from my SM-N950F using Tapatalk

[Shock]

Yeah it sort of looks like there may be an image there messed up.
I'll have to pull it apart again and position it better to get at the Tcon, it's currently buried under the BAX board (main/graphics).

[Shock]

Well it's half working.

[Shock]

I swapped the Tcon cables over as well and checked they were both functional and the fault follows the left side of the Tcon (which is the right panel side). I'm taking bets, hints and predictions at this stage.

[Shock]

Going to take some measurements tomorrow and compare the two sides.
Want to deduce if it's somewhere on the Tcon causing the issue or on the buffer boards (painful).

Has anyone got any service experience or info on what measurements I should be seeing on this specific Tcon? Sonys number of this board is 5550T20C01.

Many test points but nothing very descriptive.

[Shock]

Checked the two identical sets of 9 HC/LC/ST test points on the left and right Tcon cables and the larger 14 VGA test points. When the panel is running with the working side only connected or no cables connected measurements are shown as below which looks pretty sane.

When the non working side is connected by itself or with the both cables connected, most of the test points voltages are all over the place.

So I'll go out on a limb here and say at this point it feels like it's not a problem on the Tcon board and feeling like one side of the vertical buffer board on the panel.

(readings approximated)

HC6 2.1v
HC5 2.1v
HC4 2.1v
HC3 2.1V
HC2 2.1v
HC1 2.1v
LC2 29v and -9v (alternating)
LC1 29v and -9v (alternating)
ST1 -9v

VGA1  14v
VGA2  14v
VGA3  12v
VGA4  12v
VGA5  10v
VGA6   9v
VGA7   9v
VGA8   6.5v
VGA9   6.2v
VGA10  5.1v
VGA11  4v
VGA12  2.5v
VGA12  0.5v
VGA14  0.3v