[morzh]

Eric

Using scope is really a simple thing. You pretty much connect two grounds together (the scope lead's GND and the Chassis) and then put the probe to the point of interest.

Of course in case of tube radios you have to observe the basic safety, like not touching the two grounds with both hands etc, using an isolation transformer if the integrity of the isolation is in question (or even if it is not) etc.
Use proper V/div setting to not overload your scope input, in your case at least 10V/div and use AC coupling and not DC in this case as you do not want to adjust hundreds of volts every time you move the probe and you are only interested in the signal itself.

This is as much as there's to it.

Again, be safe.


This said,

1) connect the two chassis together (probe's GND to chassis). Better even do it when both scope and radio are unplugged from the Mains.
2) Set your scope to AC coupling (a mech. switch on old scopes).
3) Set to 10V/Div
4) touch the probe to whatever the output of your oscillator is. If it is the plate load (the transformer etc) - touch the plate. Proceed from there.


Have you put the sch link here yet?