There are a few ways you can approach this. One involves an instant fence system which may take care or the problem and another method would be a scat mat. A scat mat and most instant fence systems us a small electrical shock to keep a dog away from a certain object. Now they do make some instant fence system that use a spray of citronella. I always ask an owner to let any shock device shock them first so they see the intensity of the shock is not high and that it is the unexpectedness of the shock that stops the dog's unwanted behavior.
What these devices would do is that every time he got near the tv, he'd go in range of the instant fence or step on the scat mat and get an instant reprimand for attacking the TV. This is immediate and you would not need to be there. Now he may stop sooner than the tv and start barking instead but we wouldn't know that until it started. You might start training now to teach him a quiet command to prevent that from happening. I'll give you instructions on that and another method of training after I give you links to the instant fence systems and scat mats.
Often these products can be found on auctions sites as well.
An alternative method which should work would require him to be leashed and you present. Perhaps you know of a show that has animals on it that would start the unwanted behavior and use that for training purposes. He would be leashed and you would have a fanny pack or other container of special treats like paper thin hot dog slivers.
Each time he goes to attack the TV, you give a short tug on the leash and a firm low toned "NO". After a few "reprimands" he should hesitate or stop for a second. Grab that opportunity to reward him with a hot dog sliver for not attacking the tv. This combines reprimands with rewards for the desired behavior (not attacking the tv). This method takes a lot more time but as the dog realizes that he gets special treats when he doesn't attack the tv, training progresses quite quickly. Spraying him just gave him a reprimand and it was not instant or Consistent, the methods I have suggested either are instant and consistent or involve both reprimand and rewards which show the dog the desired behavior.
I did mention teaching your dog the quiet command in case he starts barking at it instead of attacking. As crazy as this sounds you may wish to teach the pup the speak command and then the quiet command. It seems easier to teach the quiet command after the dog has learned the speak command. The following site explains teaching speak and quiet commands.
Clicker training also provides an interesting technique for stopping excessive barking which you can read about here:
Hopefully this gives you some options to stop the unwanted behavior. I sincerely ***** ***** this information is helpful. If you are satisfied, please remember to rate my service by selecting the 5 stars at the top of the screen. If not, we can continue here until you are satisfied, simply use the reply box and let me know. Thank you!