Decoupler test tool

[Murphyv310]

Being fair there in no reason why the heater chain shouldn't be broken for this test. The proviso is to reduce the HT with a variac and in the case of a PY33 or other valve rectifier adding a temporary 1N4007 or external HT supply. Keep the HT at the sets nominal voltage to reduce any stress on capacitors.
It really is a bit of faffing around TBH as so many 60 year old caps are well past their use by date anyway, and should be replaced.