In article , N_Cook
writes

This 300W amp blows correct T3.15A fuses every now and then at sw on. The
owner left in the last one so I can see it is just "tired" , neat break and
2 constituent parts of fuse wire remaining.

We have a similar problem at work with cryogenic coolers, which are more
or less like a fridge - a compressor and heat exchanger. Like you say,
the fuse doesn't blow, just parts cleanly due to inrush surge at switch
on.

Any issues concerning putting in an ex pc SMPS 450W, 250V land mains inrush
thermistor, unknown specs, other than 14mm diameter, 4mm wide , 1mm diam
leads, 8R cold , 1R after 20 seconds touched by soldering iron barrel.

Don't see why not. Or a 1 ohm wirewound resistor which will dissipate
3.15W at peak, so use a 5W one. Mount it in free air, of course.

will mount on small high temp board and wire into the neutral
side of the wiring,

Why the neutral? Just curious.

Are polyswitches used in these circumstances , ie not purely "fuse"
action or generic name for devices specific for this purpose?

I would say they are unsafe for use on mains, simply because they
reconnect the current when they heal. If there is an actual fault in
the equipment rather than the inrush current blowing the fuse and
disabling the supply permanently, it could lead to a fire.

--
Mike Tomlinson