[RodB]

Try checking voltage at pin 5 of the 12SA7 with a DMM. You should measure -2 to -4 volts if the oscillator is running. If it's zero there's the problem. Start by re-checking the oscillator solder connections, coil continuity, clean tube socket pins, pin 4 should measure B+. The capacitor connected to pin 5 is usually a mica and sometimes it can fail. There's usually a 22K resistor connected to pin 5. If it's more than 24K, replace it.