My first partner wound the toroid coils, took 2 to 3 hours....Then we bought some, $12.50 each...Then I found some for $6.50..Easier to buy a circuit from C&H...
That wimpy little coil in the picture won't last as long as a real one...Weak insulation....They were/are made for about 3 volts, the CD circuits put about 300 into the primary, put out 20,000+, enough to spark over 1/2 inch in dry air, depends on the current draw, somewhere from 150 to over 300 MA.....At some point the spark jumps from the output wire about 1 inch along the coil, looking for a ground....I have seen a bakelite carb insulator with a 1/8 inch deep track burned into it when the owner of the engine grounded the coil to the carb bolt..It's insulated, so the spark just followed the path of least resistance, the bakelite block...Usually the sensor goes out first, but this one didn't..Wish I could find some sensors like that..