At first, I was a bit confused because the schematic he provides in the first link there (the argentine one) shows one 75ohm resistor on each line off from the video encoder, but in his photos there are two resistors on each wire. But apparently, two 150ohm resistors in parallel is the same as one 75ohm resistor. I learned something new today. I have no idea, however, whether there is some advantage to doing it this way, or if he just had a bunch of 150ohm resistors laying around and no 75's. In the youtube vids and the sega-16 page, the mod is done with a single 75 on each line.
There are three reasons why someone might use 2 (or more) resistors in parallel/series, instead of a single resistance value.
- one, to construct a non-standard value.
**this is probably the most likely reason for the installation you saw. 75 ohms is only available for resistors with a tolerance of <=5%, while resistors with a tolerance of 10% or higher are cheaper in cost. F.Y.I., If a resistor has four bands, with the fourth band being the color silver, it's a 10% resistor. If a resistor has five bands, it's a 10% resistor when the fifth band is the color silver.
- two, to spread heat (a.k.a. Watts) over multiple components, instead of torching

one.
- three, the circuit designer is making a voltage divider.