This wiring diagram is taken from my 1983 Rainbow II, it should also work with the Prestige 150 and 250 as they have the same controls (3 way switch, 2 volume and 2 PEQ tone controls). The volume pots are 500K log/audio, capacitors C1 and C2 are 0.022 microfarad Mylar. The PEQ tone pots were specially made for, and patented by, Matsumoku. They are not a standard part and there is no commercially available equivalent today.