[Richardgr]

A simple example of an improvement is the substitution of difficult to source valves with equivalent, later alternatives, that were invariably rated a bit higher then their forbears. Or using X and Y rated caps as replacements, or any replacement of a out-of-spec passive component with a modern alternative.

What would an extreme example be? I suppose gutting an old device, and just using the housing, with a modern device 'under the skin'. That would not be acceptable, IMO.

I think it is dangerous to be over zealous about 'originality', otherwise these old record players and radios will not be repaired, and will end up being dust collectors, and safety organisations will have us declare them on our insurance policies and put cages round them.

At the end of the day it is how 'inclusive' we see our hobby, as time progresses and the ability to 'keeping it original' becomes ever harder.