$29 Oscilloscope, always wanted to see a spark Options

[worn]

I have had squirrelly ignition problems with the rebuilt 911 and the 2056 teener. In both cases a key problem was that a new part was assumed to be a functioning part. This is electrics, so I should have known better. Having taken LC circuits in physics 40 years ago I figure I know how to push electrons. Again not necessarily so.

At any rate I found an Amazon deal on a oscilloscope kit for $29 shipped. Except the price includes an extra $4 to have it shipped already assembled. I am too old for surface mount soldering (IMG:style_emoticons/default/blink.gif) .

And here is the spark trace from the 914:


To get this I made a 1000-1 capacitance probe with a piece of copper pipe and a couple caps and resistors I had lying around. I followed the basic ideas here.
https://www.princeton.edu/ssp/tiger_cub/lib...n_waveforms.pdf

The basic idea is to put a slit piece of copper tubing around the plug wire with a clothespin and link that to a 1 microfarad capacitor assuming that the tubing is around a picofarad. I used what I had in the bins.

At any rate I always wanted to see what the spark was like and hope to be able to use this for better tuning. Someday. I already know that the waveforms aren't even. Haven't spent enough effort to determine how consistent this is - may be a limitation of the number of places available on the screen and thus limited resolution.