[Arran]

In terms of servicing, DO NOT power it up with the speaker unplugged, unlike most sets the B+ is not completely disconnected from everything with the speaker removed. As a result you will end up with an elevated B+ voltage going through several parts and potentially burning them up.
Also there is a 15 - 20 watt resistor that goes between part of the B+ circuitry and ground, this is what used to be called a bleeder resistor, it's very common for this resistor to fail. I've never had my Canadian 3118B working as yet but from what I have heard the 18/118 series chassis are a very efficient design and a good performer. However the 118 is an updated version of a model 18, so I think that's why is has some archaic things like that bleeder resistor and a rather unsafe B+ supply.
The Philco service diagram also has some errors in it in the power output stage, I think it relates to how the #42 driver tube is connected, refer to the diagrams with this same power output stage for reference.
Regards
Arran