Help detecting display malfunction. LCD Cable or Graphic card?

I have an Acer Aspire 5810T. Lately the lcd sreen stopped working. I've tried connecting the laptop to an external screen and it worked fine with this external display.

Then I tried my laptop screen on another laptop and it worked fine on the other laptop.

Then I tried the other laptop screen on my own laptop and it didn't work.

So, because my Acer Aspire 5810T screen works on other laptops and my laptop works fine using an external display I think that the LCD
cable could be the problem.

Before I buy a cable, could you give me a piece of advice from your experience?

Many thanks in advance.

PS: I do not send it to the manufacturer because it's out of guarantee and it would cost a lot more than it's value...