See if shows in 'lxrandr' settings>monitor (If I remember).
I have a laptop like that also (it shows) turn on output and disable other monitor, will still run laggy (remember also the resolutions will be lower(800x600 if old style TV in USA))
also had one TV would be in Black & white only unless actually installed with other output disabled/not connected).
P.S. I like to put various "Linux's on old computers then give charity.
found "Peppermint' best for making (playing movies, flash ect) media type box on old style TVs.