Screen splits after any stress on gpu

[scaanasaki]

Hy
I just bought a used GPU an AMD HD 6850 (sapphire (its a OC version which comes with 2 6 pin)) so after installing it and all the drivers i want to test it so i downloaded furburn (a benchmark tester) so acter i started the test the GPU didnt show any problem till it goes to 60-80% of the test and boom the screen become full of lines like in the pic and after i swiched to the VGA from the integrated GPU i got a blue screen on windows 10 i reinstalled all the drivers and same problem and when i restart the PC it becomes normal again and when going on a game the screen splits and the left quarter go to the right or the lines apear (vertical and on the hole screen)
I added a new windows 7 hopping that the win 10 is the problem and after all the drivers r installed same problem ;-;
Any solution or did i just got a dead card ?

These are the Pics: https://imgur.com/a/lePIm

 

[RememberThe5th]

What is your power supply?
Did you clean the GPU and repasted and changed thermal pads?
How did you connect 2 6pins to GPU with single cable or 2 seperate 6pin cables?(Yes this affects stability)
Any previous cards that you might have?

 

[scaanasaki]

What is your power supply?
Did you clean the GPU and repasted and changed thermal pads?
How did you connect 2 6pins to GPU with single cable or 2 seperate 6pin cables?(Yes this affects stability)
Any previous cards that you might have?

A thermaltake 650w psu and i connected both of the 6 pins and did not clean it or opned it cuz am afraid that the seller ll tell me that i Brock it after oppening it so i dont really want to do that and about the 6 pin 1 of the 6 pins is out of the other one

 

[scaanasaki]

https://imgur.com/a/Yzr7p
This is how it is connected and my psu

 

[scaanasaki]

And when i play an old game like GTA sa on on vert high i get 90 FPS and no problem soo ??