James :
In simplest terms, the ballast resistance is needed to limit the current
through the coil to what the points can handle, once the magnetic field has
built to it's maximum value. Otherwise the points (or point amplifier like
the Crane XR700) will overheat.
Randall
erl@unix.mail.virginia.edu wrote :
>
> Can someone tell me the function of the ballast in the circuit? Some
> coils come with them installed, some, such as the TR-6's,
> have a ballast
> wire or similar device. I know that it will drop the voltage
> across the
> coil, by why is this necessary?
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