SamyGO

Sad, I wish you enabled debug mode before. I don't know if uboot working on your TV or not. But worth to try.
If that USB to Stereo jack cable is real ExLink cable, will work on your TV modal. But if it doesn't write anything on it that cable, it's probably USB soundcard, not work for your TV...
You can also make that cable by yourself, schematics in wiki page.

Jusiz, do you have any hope for this user?
bricked++;

I think, you have wrong cable. I did`t hear about usb to jack 3.5 cable is being used as exlink. You can`t get TV access using such cable.
1. You need serial to stereo cable where wires are joined directly as it is shown in schematic. You can easy make such cable by your self.
2. Yes, you are right, we connect to TV over telnet, but you need com port for that (so called serial conection with exact connection settings).
3. If you did not set anything in service menu before (rs232-jack set to debug is needed), here is one more chance to enter debug mode. Open back panel of TV and here should be "debug button" directly on mainboard. Or if not, here are contacts to join (do short connection) and get debug on I need good resolution photo of your mainboard.

So, at first you need to have working serial cable. You can check if it works properly by joining tx and rx wires and open terminal window, choosing right serial port (com1, com2 or other, depends on with port is cable connected). If you get characters you`ve entered on screen, then cable is ok, you can try connect to TV. I suggest you use puttyas terminal client.

Yes, you are right!
If you get success, you should get log from TV in putty window and after you enter "debug" and press Ctrl+c, it should drop you to shell. That`s the idea

hmmm...
curently i`m out of ideas
must think... but if you do not get signal over exlink, nothing to do. Debug button resets micom and tv reboots. And after this you still cant enter "debug" with success?
You could try reset eeprom like bad settings in service menu have been set, but it is not your case...