Are you getting the continuous sparking and the transistor heating at the same time?

Have you tried reflashing? If you're using the spreadsheet hex, try compiling the code and see if it makes any difference.

And just to make sure, the reason the transistor is heating is because the PIC is holding the output low for too long? So pin 6 is low for too long, which is turning Q2 off, which is causing the SCR to stay on, which is allowing the capacitor to drain, which is allowing power to flow through the transformer, which makes Q3 draw too much power and over heat. Do I have that right?

If that is the case then it must be that the GPIO for pin 6 is out of sync and I guess it must be reversed from what it should be doing. It must be staying off all the time and only turning on when it should be firing the spark. If that's the case then something must be disrupting it so that it misses a change and is running opposite what it should be. I'm not sure how that could happen, I'm setting the bit rather than flipping it, so it should be fine the next time it triggers.

I'll keep looking into it. Everything always seems to run fine for me, except for that one time. I'll keep trying things and I'm sure it will happen again at some point, then I can study it further to try and get a better idea of what's happening.


-Jake