28-07-2020, 01:08 PM
(27-07-2020, 08:47 AM)Murphyv310 Wrote: Hi.
The transistor was a 2N2955. In fact I made a couple with 2N3055 later on for negative earth and ballasted coils with no failures. My 1986 Skoda 120 LSE was the last car I had with this fitted and it used the 2N3055, previously to that I used line output transistors.
The key is of course CX if its missing or low in value then there is a greater chance of the transistor failing.
Hello Trevor,
Thanks for the the info on the transistor. I will get the stuff together and build the circuit. I will have to get the flywheel off to get at the ignition coil primary. There is a small aperture on the face plate of the flywheel but it's only big enough to adjust the points if that. I've already had the flywheel off. I was very pleased to find the puller for this amongst my tools. My father made it about 50 years ago. It's not one of the three fingered ones but instead is a barrel, threaded on the outside to fit the tread in the recess of the flywheel and threaded down the centre for a bolt which pushes against the crank shaft. It' a bit of a one of. I only mention this as at the moment I can't find it. I have noticed this since I started on the scooter. I don't really have enough room to have it both stripped, store all the tools and work on it as well as having other stuff in the garage and so things get lost. They usually turn up when I'm looking for something else. On the issue of a battery I assume I could test this circuit using 4x1.5V AA Alkaline cells as long as they were not connected in any way to the charging circuit. My initial thoughts on testing was not to try starting the engine but to kick start it with the plug out and look for a spark. I know I would get one from the magneto if the circuit didn't work but if it did I would presumably see less/no sparking at the points .
@Cleggy
Quote:Back in the 1970's, there were lots of magazine articles and various kits to add electronic ignition to cars.Yes I remember those and also kits one of which I built and fitted to a VW Beetle. As I remember It was a bit more complex than just doing the switching. I seem to remember it was supposed to supply more than 12V to the ignition coil primary which in turn was supposed to provide a better spark. I think it also lengthened the dwell. I think it retained the original ignition capacitor and you could switch the whole thing out and go back to just points. As I remember it was an improvement.
@BusyBee
Quote:Simple engines used to use the battery for regulation which was Ok but obviously there was no charge regulation.That's exactly how this scooter is set up. I have wondered about how changing the failed metal rectifier to silicone, which I think will give a higher output voltage, will affect the charging of the lead acid battery (when I get one) not to mention the affect on 6V bulbs which I think will also be harder to get now.
I am still finding it hard to get my head around what's happening here. The Magneto is generating an AC current as the points switch the ignition primary coil on and off. With Trevor's circuit in place DC current is used to switch the ignition primary coil on and on and off. Will AC current still be generated in the coil? If so will it affect the DC circuit in any way?
Regards,
Ken.