rectifier(GZ 34, 5AR4, or 5U4) is right in front(looking from the back) of the power transformer. KT88's or 6550's are your power tubes(2 big sockets in the midle) 6AN8 is the phase inverter(Ithink) little socket in the middle, and 12AX7 or variant is the preamp tube behind the output transformer looking from the back. I know this because mine (200s - same as sonaro) is in pieces right now waiting for a new power transformer, just got my tubes though, getting closer!