Rider 6-18, without a scope, in this non working radio can one check for a short on the two gang variable condenser??

With an ohm meter, tuner fully open, one lead on the frame, the other lead on the antenna lug connection. Turn the tuner, if it shorts the meter will show that. Do the same thing on the oscillator side lug. Normally a visual inspection with a magnifier glass you can see any gangs touching.