And what about other HDMI ports , do they also drop out? If its not a port issue , than do what they say above , and also try different cable...

Its common knowledge to disconnect power before you try disconnecting the cable of main board , but that shouldnt have damaged it , if you are getting nothing now , maybe go and inspect the solder contacts on the power board , because when you removed the connector you might have flexed the board exposing the issue further... try to inspect the whole board for cracked solders and reflow accordingly... Also clean the dust off the high voltage side , its not helping anything...

Also in Service menu it says it has 600k im assuming minutes on time , i think this tv was on its whole life, 10000 hours is crazy , maybe not i dont know... ehh , this is going in the parts bin... It even has a energy sticker on the back from the stre , looks brand new too... I got this TV out of a business so it was probably in the store front or lounge...

VGL - (-6v)
AVDD - 15,8v
HAVDD-7.5v
VCC3v3 -3.3v
VCC1v8 - 1.8v
VCC1,2v - 1.2v
VCOM_L / VCOM_R - 7volts

Tried freeze spray when screen goes to crap , no change , tried freeze spray on tcon aswell , no change.
when i plug in only one side , either i get nothing on screen or just same crap as before , tried the tape trick on all pins , both lvds didnt do much either.... At this point im really sure its just trash screen...

I'm gonna dump the firmware and upload it to the Russian remont website if anyone ever needs it

I changed all three flat cables , and that's ruled out , at this point I'm pretty certain it's the screen fault...

Here are the pictures...

I got this 50 inch tv the screen starts off with almost nothing visible but the top part of it , and it would slowly kick in and the picture would be visible , but then over time it would go greyish with the top of it mostly intact. I did have instance where the screen would be fucked like that and i would touch the cpu and memory to see if it would react and a couple times it would screech on the speakers and restart. After that it would show a better picture somewhat but afterwards i touch the cpu and not much is achieved. Im wondering is this a screen fault or should i pursue this with a donor...