I seem to remember Panasonic technical recommended changing both items even if just one was faulty but could often get away with changing the Magnetron if it was just cracked magnets.
if you can see the mag heater working when you turn down the lights and disconnect internal lamp chances are inverter is ok
if its blown a fuse chances are inverter is knackered although I always try a 6.3A fuse with just inverter in circuit to see if it blows. 99{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} of the time it has
Thanks electrofix,
Mag heater on’t work as it blows the fuse immediately. I will try just the inverter with the lower rated fuse.
With regards to the mag, I notice connect do a variety of 2M236-M42 at varying prices, cheapest being 5045175191141 at £44.52. Am I right i thinking any 2M236-M42 will work with an inverter board?