http://en.wikipedia.org/wiki/Latchup
Ideally Pin 16
should be 75ohm - however it (75 ohm impedance) can be achieved in different ways (for example dynamic impedance - current source) - with 12V on rail it can be problem - better is to reduce voltage provided to pin 16 (for example Zener diode, LED can be used also as a voltage limiter - additionally it will show power on ).
510ohm resistor with 75ohm impedance will create
correct voltage but impedance must be "ohmic" type and should be constant.
IMHO fully relaying on Pin 16 as a pure resistive 75 ohm impedance is not safe assumption - it can works on 1000+1 TV but on 1002 will fail...
side comment
SCART is good example how to not design customer interfaces - bulky, low quality, with odd voltages when compared to signal levels... but it was designed in first half of the 80's and if you see schematics for TV's equipped with SCART from 80's you will see why those strange voltages was used... SCART - revenge of Frenchmen
