[Radioroslyn]

here's a couple of simple things to check. Connect your ohm meter to the stator of the tuning cap (osc section) and the chassis. With the cap completely open note the resistance. Slowly close the cap and watch the meter for any fluctuation in resistance (lower rather than higher). This would be indicative of a short between the stator and rotor plates. From what I can see there isn't any coils connected across the tuning cap so I think w/the cap open your going to see a pretty high resistance to start with.

Is the band switch cln??

Use your tube extender and measure the pin voltages on the 6A8 to see if they are close. Just for grins check the osc w/the 6N7 removed.

If you want a fun toy I have a spare programmable frequency counter. This can be easily connected to the osc output and can tell you it's exact frequency. It also can be set  up to display the exact frequency that the set is receiving (digital dial) which can be handy for doing the osc alignment. You can order from China but in takes abt 3 weeks to get here. If interested pm me.