[morzh]

Thinking of it, what could've potentially happen was that a larger than necessary capacitance, when connected to a high voltage, created inrush current through that pot that exceeded what was acceptable. This would not happen if it was connected to a, say, a grid voltage via bias resistors that are high in value, but if you accidentally connected it to a B+ plate supply that would be able to do it. This is where a lower capacitance might've saved the schematic due to a lower inrush.

Anyways, if you point us to a sch of your gen, we'd be able to try to point you in the right direction.

As for the value of that cap, in the future try to use the smallest possible value that still give you acceptable impedance at the lowest RF frequency: this way you both can provide an adequate input for your RF amps and avoid a destructive inrush no matter where you decided to touch your receiver.