Update :
Kept glaring at the dead coil,knowing full well that they are a non-servicable item. Looking,turning over,putting down,picking up again. Whats that ? Tiny black spot on the top of the positive terminal stud. Scrape scrape, its a hole ! I reckon that when they are assembled, the 2 ends of the windings come up through the centre of the studs, the ‘bakelite/plastic top, crimped to the tin can and the terminals then soldered. Except that one of mine wasn’t, or barely. Quick resolder job, 2.5 ohms resistance, and normal sparking has been resumed. Hooray !!!! 😀
