[Chas]

I would suggest doing resistance checks of the power cord up to the switch and transformer input. If all seem well no shorts or opens. Look to see how the ballast tube is wired to the power cord as well it should be in series that is if it is correct.

If the 81 is incorrect, that ballast may well be too and were put there as "hole fillers"

Then, power the radio with the ballast in and the rectifier tube the 80 removed there will be no B+ but the tubes should light, there should b no noises or other heating of the power transformer, the ballast should be warm but not HOT. That test should take some 30 minutes to do. If all is well that confirms the power transformer is good..

Now do resistance checks of the B+ locate the filter pack and what needs to be done to replace the filter condensers. You must also determine if there is a speaker with a field coil that is missing. The field coil is often part of the B+ filter network. There may be a tube socket associated with the speaker and it will be for just the speaker. Often it is a special configuration socket so a tube cannot be plugged in. The radio may use a magnetic speaker, so some tracing and note taking can determine that.

There are other "gotchas", if an RF coil is open it will have to be re-wound, checking them should be relatively simple, most often they are not more than 20 or so ohms. There are also AF transformers, these can go open too. resistance checks of them should be done with an analog meter looking for no more than 8K often they can read 250 ohms on a primary but no less. More than 10K will likely mean an open winding.

Steep learning curve on this radio, made all the worse as there is no schematic as yet...

GL

Chas