I've noticed it mostly on late 40s knobs. It's not really a strong smell. I first noticed it when I opened a small box of knobs that had been sealed for many years.
I've been studying that 505 schematic and it does seem pretty close to my sets other than the 6SH7 tubes. Weird design. Especially the power supply and HV portions.
Here are links to a schematic I scanned from Most Often Needed Television Servicing Information 1948 edition.
http://www.bobandersen.com/images/ha...5%20sch-01.jpg
http://www.bobandersen.com/images/ha...5%20sch-02.jpg
Phil - any concern about the series wired 7JP4 filament?