I found the surprisingly in-depth manual online which even includes a schematic. The V1 is the preamp for the rhythm and lead channels. The V2 is used on the lead channel only. The V3 is the phase inverter. The reverb is op-amp driven. I could tell from futzing with the tone stack that they are active cut/boost with 5 being flat. From the sounds of it the "Hi Lead" mode (when you pull the master volume) seems to be another version of a bright switch.