[mikethedruid]

Looking at the schematic for similar models, PT2, PT6, and PT12, I would carefully trace all the filament wiring which is a series circuit. I would also look at both sections of the candohm resistor, or, better yet, just go ahead and replace it using a terminal strip and two resistors, an 80 ohm of at least 5 watts, preferably more, and a 40 ohm of 3 watts or more. You could buy 3 40 ohm (or 39 ohm) 3 watt or more resistors and use 2 in series for the 80 ohm section.  Several places carry them, here's a link  to get you started, https://www.justradios.com/
[url=https://www.justradios.com/][/url]