A transistor basically consists of three layers
of a semi-conductor material (a material
that will only conduct current flow under
certain conditions).
In this diagram, current can not flow from the negative terminal
of the battery,
through the coil, and back to the positive side of the battery until
the transistor is
"switched on". To turn the transistor on, a small current flow is
applied to the Base.
Once this occurs, the Collector-Emitter junction is completed, and
current can now
flow through the transistor. If the Base current is turned
off, the transistor is also
immediately turned off, breaking the circuit.
Applying this to the ignition system:
In this diagram, note that the ignition points are placed so that
the only current flowing
through them is the small current required to switch on the transistor
junction. Because
of this, point arcing is eliminated - resulting in rapid field collapse
and longer point life.
The points are still controlled by vacuum and centrifugal advance
mechanisms to control
spark timing.
Problems?
The points are still opened by a cam, and as a result will wear causing
point gap and
ignition timing to change. This results in poor performance, poor
fuel mileage, and
increased emissions. So what was done to help eliminate these problems?
