Yes, the LED lights fine and when it didn't light at first I turned it around. The 10k variable resistor doesn't seem to adjust the frequency very much but I think it will be fine. I'm glad I picked up three coils since I just smoked one. I'd be happier if I had taken all six. I left the power on and sparking for about a minute or so when it quit.The coil's heat sink was very hot. We'll see if it recovers after it cools down. Somehow I doubt it.
Thanks for the circuit, Rotarymaker. I'll give it a try.
Not a problem DustyB, hope it works for you.... if not get back to us.
Another thought on your coil burning up.... make sure you have a sparkplug in the coil with a max gap of about 1.2mm.
If you are just arcing it over a longer distance to earth/ground, that'll surely cause coil failure, as the high voltage will always take the path of least resistance and arc and carbon track its way thru the internal coil windings.
Also make sure that your max frequency output of the 555 is within the range of the coils design
ie normal car, say max rpm = 7000,
at firing once every 2 revolutions (4 stroke) ..... = max 3500 sparks per minute
.....divided by 60....
= approx 58 hertz or 17millisecs period
.....hope I've got the sums right!
Nevertheless, too high a frequency will cause failure of the COP internal driver circuit.
Rotarymaker