[Arran]

I would try working on the 38-620 first, it's a six tube set rather then nine so less complex in that way, less wires will need to be changed, and provided that nothing catastrophic has happened the power and output transformers will not need to be replaced. While the RF sub chassis in the 38-620 will have some burried parts the 41-256 also has parts burried under the push button assembly, so six of one and half a dozen of the other, but at least the wires connecting the sub chassis in the 38-620 won't start crumbling insulation as soon as they are disturbed. I must say one thing about the 1939-42 Philcos though, compared to a 1932-33 RCA set they are much easier to work on.
Regards
Arran