Valveholder?
I have often found pins on this series of valves need a good clean. If you pull the valve slightly can you measure 270 ohms to chassis fom the cathode pin of the actual valve?
If you have a good 6V6 knocking around you could always connect one in temporarily on the end of some long wires soldered to the back of the 7C5 socket, just to prove the set.
If you do scrap it, can I bagsi the Mw/LW oscilator coil please?