In detail, When we say watch TV, we usually refer to we watch the videos, images played by the machine, or you can say TV set, not the machine itself. However, in daily life, when we want to express the machine itself, we also say 电视，too. So 电视 includes 电视 and 电视机。 Have you got it?

电视机更强调了固体【solid】的感觉，电视【program】则有了虚拟的节目的意思，所以一般是看频道而不是看机器

电视=电视机=节目，电视机=硬件

电视机= Tv set 电视=Tv set;Tv;Tv programm...

电视 = TV 电视机 = TV set. And there is a big difference in meaning of the two as in English. You watch TV but you don't watch the set.