Josh, is this the version with the built-in power supply? It has an EZ40 rectifier. If the HT is slightly low, it could be stopping the oscillator. The LT for the valves is derived from the HT via a dropping resistor and various ballasts. Typically these little battery valves are rather critical on their supplies and it may be that the filaments are glowing just sufficient to keep the audio active but not the mixer/oscillator. Measure the HT on the output transformer. If it's much below 80 volts then probably a new reccy is required. All the filaments are in series and add up to 7 volts (the DL94 is a double filament with the sections in series so it's 2.8 volts rather than 1.4 like the others). So if you measure across the filament chain you should read somewhere near 7 volts if everything is OK. Be careful when measuring. The valve pins are rather close and it's easy for the meter prod to slip...popped filaments.....
!
SB