Re: Ballast resistor

[Darrel Kline <darrelk@domain.elided>]

Steve S. wrote:
>Tom,
>
>I was playing with my points when my MSD failed.  First I tried to wire 
>it without the condenser.  Nothing! Put in the condenser, Perfect! Then I 
>began to think about why I needed the condenser.  
>
>When the points break the current flow to the coil in order to cause a
>field collapse and generate the spark, the condenser serves as the ground
>portion of the circut for the secondary side.  The coil isn't grounded
>throught the case like I thought it was.  As the field is collapsing, the
>current behaves as alternating current, not the DC we are all thinking 
>about.. Thus the condenser serves as a path to ground. 
>
>Look at the circut sometime.  Check where thepossible ground paths are.
>
>Steve

Some coils do have one side of the secondary grounded to the case, depends
on that particular ignition system.

If you apply DC volts to a transformer (coil) you won't get a output on the
Secondary. You need a expanding/collapsing field, which AC current
provides. In an automobile application we used *pulsed* DC, which isn't
really AC because the current doesn't change direction. 

Darrel Kline
Colorado Springs
1980 Scout II