[Radioroslyn]

There's two reasons I can think of to ground one side of the heater winding. One cost reduction as there is a bit less copper wiring to do with it grounded And the other hum reduction. THere's a few different ways to go. One is the float both ends and ground the center tap. Another is to ground one end and float the other. And a third is to float both end and twist both ends throughout the set. Perhaps the designers @ Philco determined that grounding one end was cheaper and less noisy than the other methods.

On the 84 it's not particularly it's not critical till you get over to the 2nd 77 tube (detector). It's a hi gain and hi impedance circuit and is prone hum pick up from ac fields hence the tube shield.

Philco sets for the most part use an odd voice coil impedance (abt 1 ohm) as compared to most sets (abt 3-8 ohm). It's not much of a big deal but though I'd mention it. Would recommend use dynamic spkr rather that a pm style for better filter of the hv.

GL