[Arran]

I will add one more thing. Could not having the speaker output plugged into the chassis be causing my issues by overloading the rest of the circuitry? I could try plugging it in and powering up later, just thought I would throw it out there.

Now that I look at the schematic, yes it could, if you look at part #61 and part #62 you will notice that with the field coil disconnected they form a path to ground for the B+ supply. As with anything electrical the electrons follow the path of least resistance normally this is the field coil, with the field coil removed it's now that pair of resistors. It's a weird design compared to most sets, normally the output of the first filter cap goes straight to the field coil and the output transformer but these guys added a resistor network on that side of the field coil as well.
Regards
Arran