[TR] Ballast resistors and Electronic ignition

[Randall]

> ballast resisters were used with points ignitions in the 60's
> 
> when everyone went to electronic ignitions in the 70's... 
> they lost the 
> ballast resistor and the 2nd hot wire from the solenoid...

Your dates are rather off, at least with regards to Triumph cars.  60's
Triumphs did not have external ballast resistors, but instead used coils
with internal ballasts.   The external ballast and "2nd hot wire" were
introduced in the early 70's, to make starting easier with the added burden
of smog equipment.

> I mean what is the amperage draw through a Pertronix Ignition 
> Modual?.... 
> 100 milli amps max? Over heat the coil?

The current through the coil (and Pertronix module) is several amps, not
just milliamps.  Since the Pertronix in effect shorts the coil terminal to
ground, the ultimate current (after the coil inductor saturates) is limited
only by the DC resistance of the coil, and the ballast resistance.  A
typical "external ballast required" coil has a DC resistance around 1.5
ohms, so we're talking current of nearly 10 amps.

> This is a 76 TR6.. it allready had electronic ignition... there's no 
> "hidden" ballast ressistor...

The factory documentation does not agree with you.  Nor does Dan Masters or
any other source I'm aware of (including my personal experience).  The TR6
was never fitted with electronic ignition by the factory (hence the
popularity of conversions like the Pertronix), and all TR6 from 1973 onwards
had a ballast resistance incorporated in the wiring harness.

> the ones I've replaced are as big as my thumb 
> and usually mounted to the firewall next to the coil..

Some Triumphs did have discrete ballast resistors (like my 71 Stag, although
the Stag had it mounted to the coil on the engine).
http://tinyurl.com/ywem3h
But not the TR6.

> I do agree that the coils probably should be matched to the 
> system,

Converting to a coil that does not require an external ballast is a viable
option for most electronic ignition conversions (though not all of them).
OTOH it doesn't solve the problem of finding a switched 12v source for the
Pertronix, and just adds cost to the conversion.

Randall