David Billington wrote:

I don't know the welder but a friend has a small MIG with 2 switches to
control 4 power levels and it appeared to stop working. After we spent
several hours checking the internals I realised that the power switches
effectively had a centre off, whether intentional in the design or not,
one had got knocked to the centre position and that did it. Put it back
to an appropriate setting and all was OK.

Thanks for the input. I had a good old fiddle about with it checking for
loose connections and playing with all the switches but didn't come up
with anything like that. I suspect a faulty thermal cutout as SIP's
website says it has one fitted - especially as the cooling fan still
runs, which would be logical if the machine thought it was too hot.

Interestingly, the Clarke 120E MIG I had before never once cut out,
despite not having a fan fitted.