[codefox1]

Well, I power the set up slowly, and if I get a howl, I know I have made a mistake. Incidently the polarity of the secondary sometimes matches the norm (black ground, green 4, purple 8 if multiple secondaries) and the primary (Red-B+, blue-plate1 and if PP, brown plate2.) But not always. Some single ended sets had a reverse winding on primary to obviate a larger filter capacitor, and that can be confusing as well. Don't think Philco used them but maybe they did.

Anyway, best to leave well enough alone when fixing up an old set, and take it easy if doing a restoration. Schematic may give you a rough idea of whether you have replacement hooked up correctly.