As I said yesterday on the radio suppression aspect, a negative earth
(ground) has the suppressor lead going to negative on the coil. I wasn't
using a TR4 as the example but my PI saloon which has been negative since
new - they all were.
On the ballast resistor side of things, it appears some people aren't too
sure of their purpose, so at the risk of a little bandwidth I'll explain the
reasons for them being fitted. Firstly, they're the little ceramic cubes
often shipped along with coils. STI fitted them because of starting problems
associated with the early carbon cotton HT leads. There had been major
starting problems in cold climates (cranking related) and it was found the
HT leads were the culprit. Rather than either upgrade the leads to something
far more expensive or go back to copper cored, they lowered the coil voltage
from 12 to 6 volts. All the ballast resistor did was to temporarily allow 12
volts to go through a 6 volt coil to provide extra 'wallop' into the coil
and presumably down the HT leads too. Soon as the engine fired, the resistor
took the voltage back to 6 volts. I expect electricians far more learned
than me might be able to shoot holes in this background story but I remember
it well on a product training session when these BR's first came in on
production. I can't say anyone was too enthusiastic about them and there
were many fears they would fail and quickly destroy the coils they
controlled. To everyones amazement, they didn't - and they worked rather
well. Certainly cleared up cold start problems in Scandinavia and Canada.
Oh, yes - you still got a nice shock if you grabbed the HT leads by accident
but that was assumed to be one of the joys of Triumph motoring - sometimes
known as 'value added.'
John Mac
Book 1: http://www.toolbox.ndirect.co.uk/triumphbook
Book 2: http://www.toolbox.ndirect.co.uk/crocus
Triumph Over Triumph magazine: http://www.cyberware.co.uk/~chips11
|