[Arran]

I don't know what tube tester you happen to be using but on most of mine there is a separate test button for rectifier tubes, mind you you would know if you hit the wrong button pretty fast as the needle in the meter goes crazy and the fuse flashes. It is entirely possible that the 5U4 could be shot if the set had shorted filter caps, that's usually the first thing that dies. I thought these 116 sets used a 5X4 not a 5U4, but that never stopped Philco from swapping tubes during the production run.
Regards
Arran