it accepts vhf/uhf? it must have antenna somewhere, maybe on the inside, careful opening it up!
idk if this would work, but if you get an old vcr/dvd/cablebox that has output on ch 03 and tape the center pin (only)from output to the antenna you may get picture ....
... dont really know if it will work or if there is additional modulation encoding involved when it comes to radio waves
... maybe if the cable signal is strong enough or you have cable amplifier, you may get away with just holding the cable up next to tv , but again just shot in the dark, since i'm really not to sure about how much signal a tv receiver needs or how far cable signal bleeds out in to the air,... i do know though the boss pays alot of money to the FCC due to excess RF leakages