[Arran]

Some sets used a shield over the grid lead wire on the 1st audio/detector tube, primarily in sets that used Goat shields, or spray shield tubes, and obviously sets with double ended metal tubes, none of which made it into a Philco. I think maybe some Philco battery sets used a shielded cable on the 1H5 tubes, but I can't remember. Another weak spot, especially with double ended glass tubes, is the grid cap itself, the solder joint can go bad, even if the cap isn't loose.
Regards
Arran