What is the ruling on the landlord taking the television and receiver belonging to the tenant who has not paid the rent, and is it permissible to sell them to cover the arrears?

This issue is "the issue of al-Zafar (gaining possession)" and it permits the oppressed to take their right from the oppressor's wealth without exceeding it, if they gain possession of something from it, provided that the right is established without doubt or dispute.

Along with the permissibility, it is not permissible for the one who gains possession to benefit from the obtained item in a forbidden manner, such as using it in disobedience to Allah or selling it to someone who is most likely to use it in forbidden ways. This is because anything that is used in a forbidden manner, or is most likely to be so used, is forbidden to manufacture, import, sell, and promote.