works with scart but not rf!

I recently sold one of my saturns to a friend and when we tried to play it on his tv we realised that the saturn would not work with the rf cable however my other saturn did! I just wanted to know if this is a known problem or not? Now I need to buy a new scart cable from Lan-kwei
Maybe the +5v from the A/V out is dead? This is needed to power the RF modulator, but as far as I know SCART and composite A/V would still work fine without it.
my dreamcast even when it was brand new didnt output composite (rgb and rf work fine)

this didnt cause a problem till i brought another tv

which doesnt accept rgb through the scart socket

so its certainly possible