Your PAS could be upgraded with the AVA board for the B+ and heater supply. It would replace the old quad cap and axial heater caps and diodes with modern parts. This PCB makes for a neater internal layout. You have the old selector switch which could be a problem, it is now very old. Your PC 5 and PC 6 look good to go provided the poly caps are still OK. A few more mods and you could go another 20 years. AVA has a jack kit too. This is one outstanding preamp. Has that fat tube sound with liquidity but oh my goodness! Deep low end and nice high end.