Cap discharge

[tom cloud]

>Hi Mark
>
>Not too much help but from memory heathkit used to make a CD box.
>Also check Radio electronics mag many years ago. Cd boxes have gone
>a bit into history. 

*** how do you figger??  Seems t' me little has changed.  Someone pleez
tell I'm wrong, but we still use auto-transformers (coils) to generate
high voltages, and that voltage comes from the 12 volt supply.  Points
closed, built up mag field (dwell) and opened causing high spark volt.
Then, along came "transistor" in which a transistor replaced the points.
Better, but still crummy.  Then came CDI.  No 'dwell' current in coil.
No points to burn or transistor to carry coil current.  Just a little
oscillator to charge a cap to about 300 volts and an SCR to pulse
it into the coil.  A redesigned coil worked better, but the old ones
worked okay.

Now, seems mfgrs still sell transistor ignition (what's in the Ford
DuraSpark ???).  Then, they sell 'upgrades' that are still CDI.  MSD
is a CDI (note, all coils will 'ring' and produce multi-sparks --
I guess (or hope) they just tune for an optimum system).


Tom Cloud <cloud at peaches.ph.utexas>