snip


I must be missing something here , what is the point of the spring off
disconnect?



It opens the resistor, and removes power from the overload condition that
it's there to protect against ...

Arfa



But not if you "weld" it shut with high melting point solder

What are you saying exactly ? That 'high melting point' solder was not what
was originally used to hold it shut by the manufacturers ? Are you
suggesting that a company the size of Rediffusion, who designed their own TV
sets making use of these devices, then went on to encourage their (extremely
well trained and well thought of in the trade) engineers, to execute some
kind of bodge repair on ones that had opened ?

No, of course they didn't. If that material is what central stores supplied
to the branches for remaking the spring connection, then I think you can be
pretty sure that it was appropriate for the job. Presumably, as you found it
necessary to ask what one of these resistors was in the first place, you
have no experience of them, contemporary with the time that they were
commonly in use ?

Arfa