heres the circuit
as spec'd it should push 0.9V to 1.1V of luma into a 75ohm load.
now i suspect his tv is not providing a 75ohm load.
if he had a meter we could find out.
if his tv is 100ohm he will need another 25-30 ohms added to the luma line. (most likely)
it could also not like DC coupled luma (unlikely as most DVD players use DC coupling)