In article , G
wrote:

Howdy Nick......by your reply I can see that you know already most of
what I mentioned I don't recall power mosfets back that far but it's
possible. Wouldn't rule out that the device, especially if it's a
TO-220 or similar package isn't an SCR or similar either. I'll draw up
a schematic of an era CD box I unpotted and repaired for a Can-Am
motorcycle which is right at hand and shoot it off to you. The RC
circuit can basically be found in any basic electronics text book with
the formulas for finding instantaneous charged voltage etc....some
experimentation will be needed to find your offset though. There were
quite a few CD ignition kits around at one time and articles in various
electronic mags and project books so some digging there might be real
helpful.

Gord


CD sounds interesting but there are 2 questions; IIRC CD was sold as an
accessory to regular ignition points to take the current so the points
would not burn. The points were used to trigger the CD and the
mechanical spark advance was still used. This is all guessing from old
memories, I never used CD back then. I recall one of the arguments was
that if the electronics failed (as it did too often back then) the CD
system would revert to the regular points to keep the car running.

In addition to the mechanical advance, CD used a big cap to zap the
coil. Apparently I don't need the cap since my present system just
pulses the battery voltage.

If CD did use the mechanical spark advance it won't help me much. I
need to find a simple electronic spark delay, even if it is only a
simple fixed 30 deg delay, to pack for emergency use.

Ironically, I could really use CD for my tractor. It goes thru points
too fast, BUT it is 6-volt and positive ground and I have never seen a
CD for a 6-volt positive ground.

--
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