[Lorenfb]

"Show me the regulator circuit/component that prevents "the" capacitor from being overcharged as the battery voltage rises if you would, please. Insofar as I can see the DC to DC upconverter runs open loop."

Actually, that's again incorrect. One needs to review closely the Bosch CDI circuit diagram!!!!!!

1. The circuit is NOT the typical DC to DC converter. It is a fly-back circuit where the
output voltage over time is a function of the energy stored in the primary before the 'switch'
turns off, i.e. like the H.V. in the old CRTs. The energy is transferred to secondary which
pump charges the output storage capacitor thru the coil over time and is applied to the SCR.

The output voltage is NOT directly a function of the battery voltage which is the reason
Bosch used a fly-back circuit, i.e. It's better for cold weather low battery voltage starting
not like the typical D.C. to D.C. converter of the MSD CDI unit where the output is DIRECTLY
proportional to the input battery voltage. With the Bosch CDI, the SCR voltage over time is directly
a function of the transformer core saturation current, where I * I * L = V * V * C and V is the
pump charge capacitor voltage, I is core saturation current, L is the inductance of the primary,
and C is the output capacitor. The final pump voltage of the capacitor & SCR is limited by zener
or the RPM, i.e. as the RPM increases the maximum pump voltage is reduced.

The input zener (82V) (check the diagram) limits the peak primary & secondary fly-back
voltage with the primary collector capacitor. The voltage rating of the SCR is >600 volts
and never goes higher than about 475 no matter what the battery voltage is because of
this limit. Early CDIs had zener failures resulting in higher that normal output voltages
at low RPMs, but not the later 3 pin nor the 6 pin.

"CDI's SCR failed due to being run too long in over-voltage state."

2. Never really occurs!!! The SCR rarely fails, and if so, usually the result of shorting
the CDI output. Other CDI components cause the CDI to 'lock-up' when the
temp is high but again it functions again when the CDI cools.

"supply above ~15 volts and the SCR begins to "self-fire" (tach jumping, etc.)"

Totally erroneous! Do a bench test! If it does, there's a circuitry problem other that the SCR.

3. Some 3 pin CDIs trigger the tach from the points, so the points have to bounce
for the tach to have problems. The 6 pin CDI (911SC) triggers the tach from a Schmitt
Trigger (low voltage). Only some 3 pin CDIs trigger the tach from the coil and internal
CDI component failures, other than the SCR being over-voltaged, can cause tach problems.

A. "CDI's SCR failed due to being run too long in over-voltage state."

B. "During the drive from Seattle to ID the tach would start jumping and shortly thereafter the engine would quit. Limped the last 100 miles by alternately running with the voltage regulator connector unplugged, until battery got too low, plug in the regulator until the battery voltage got too high, etc, etc."

A & B contradict one another, i.e. So the SCR didn't fail, but only locked-up and then recovered.
That's because another CDI circuit component/components were not functioning.

Bottom line: Time to do a Pelican search to analyze (if you can) the Bosch CDI
circuit design posted many times on Pelican before making erroneous statements
and mis-leading others, please! Remember, many of the original Bosch CDIs
are still operating after 40 years which speaks to the comprehensive and robust
Bosch design given a wide range of operating conditions, e.g. voltages, & temps.