The SG-1000 II was only released in Japan, 1984. It was followed by the Mark III and then Master System. Unlike the Mark III, the SG-1000 only has Japanese RF, and not even my TV can get picture. (My TV gets picture from the famicom and pc engine)
My colleague did an AV mod, I think it is unusual and I am very happy with it.
There isn't any good schematics so he had to figure out a lot on his own.
The black contact should have been white but we only had those three colors at the moment...
The console can also be RGB modded, but the customer requested the RCA mod.