Hi: I too am wowking on a RCA 128. The best place for a set a schematics for the 128 is www.justradios.com. They will supply SHARP factory schematic which are more detailed than Riders and the price is about $5.00.
Note that the 128 had several production changes where capacitors where added or completely removed. Before ordering schematics find out what set series you have.. Good luck!