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If the set used the transformer to power the heaters (they'll be parallel wired if that's the case) one thing you can do as a diagnostic check is use a clip lead to connect the grid of the vertical output tube to the heater. The 60Hz 6.3v sine wave of the heater will be amplified by the output tube if it is good and make some sloppy unsynchronized vertical deflection. That test confirms the output tube, output transformer and yoke are OK... If you don't get some deflection focus troubleshooting on the output tube, transformer, yoke and the B+ feed for them. If you do get deflection with the grid to heater jumper then remove the jumper and focus on the oscillator.
There were a variety of oscillator circuits some create the whole drive signal in the osc tube and feed it to an output that's just an audio amp, and others (multivibrators)use feedback from the output (usually plate) to make the oscillator oscillate.
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