Resistors - not quite ten a penny!

[Nick]

That said, I can't really think of  many, if any, situations in which 0.25 Watt resistors such as these are likely to have very high voltage across them. and presumably it's the potential difference across the resistor that determines is ability to survive. Hence, if a resistor is required say to drop voltage at a point in a circuit from 250V to 150V, it needs to tolerate 100V - not 250V, or am I missing something?

So, I wonder if Nick was alluding to that particular failure mode? It might not be a safety thing as such - although arcing is possible - but it might be that projects working from more than a few 10s of volts might not have the long-term reliability you'd ordinarily expect.

I was referring to that - oddly, I also raised this point in the previous thread that you referenced: http://golbornevintageradio.co.uk/forum/...9#pid46479

Its the "rated continuous working voltage" (RCWV) that needs to be looked at...