Message text written by INTERNET:erl@unix.mail.virginia.edu
>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?
Than,s
James A. Ruffner
<
If you took your ohm meter (a pretty good one as a cheap one will not be
reliable at these measurements) and measured the resistance between the two
low voltage terminals the coil requiring a ballast will measure about 1.3
ohms whereas the coil that does not require a ballast will measure about
3.3 ohms. The 1.3 ohm coil will draw too much current and will burn up the
distributor points prematurely. Therefore an external resistor (ballast)
is added to keep the current in the necessary range. The higher reading
coil will not require the resistor.
Why did they use the low resistance coil and the resistor instead of using
the higher reisstance coil and be done with it? Using the lower resistance
coil and the ballast resisitor in conjunction with a special terminal on
the starter solenoid allows the designers to put full battery voltage on
the coil during cranking (when battery voltage is lower) and boost the
spark voltage when it is needed most.
It is a little more complicated but it improves starting (short answer)
I hope this clears up another little mystery
Dave Massey
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