Previous owner said it simply "stopped" and needed a new "card."
This is the burned component that fell off the card.
I used a Jewellers eyepiece to read the rating (3.3ohms and 7watts)and was ecstatic to find that the component was locally available for AUD1.80. A nice little saving.
I actually got a 10watt as it takes more heat. The repaired card (below) was whacked into the mig and now sweeps through its range and at all power settings.
A little note, even the higher wattage resister is getting too hot to touch while welding, it obviously is heavily loaded so I can see why the original would burn with prolonged welding. Allowing it to cool between short welds would be prudent.
Most of the smaller "hobby" migs are very similar inside. The resister is a different rating from make to make but the principals are the same.
Hope this helps somebody, in all I've got about an hours repair time in it and a couple of hours search time. Thanks to Lilly, my assistant