07-30-2013, 11:24 AM
Be careful with that because both #45s and 71As are four pin tubes, and in 1929 Philco used both depending on what chassis you had. I remember that there was a Philco 20 in a local antique shop where someone had fitted a pair of #45s in place of the 71As, they were both burned out needless to say since a 71A has a 5 volt filament.
Regards
Arran
Regards
Arran