> Date: Tue, 13 Oct 1998 13:01:00 -0700
> From: "Jarrid Gross (Yorba Linda, CA)" <GROSS(at)UNIT.COM>
> Subject: RE: Electrical matters
>
>
> ----------
> From: Kristian Jonsson
>
> >The other day I was going to test two electrical rev. counters. One was
> from
> >an Avanger and the other from a Hunter. On the back they where similar:a
> >flat connection and a pin connection. Now if you look at the electrical
> >diagram, (take the Alpine, it is similat in that area), It looks like the
> >rev counter is supposed to be in series after the ign.lock and before the
> >coil (and the whole item to earth) But it is not working that way. I made
> a
> >paralell connection, + from the ign.lock (or battery) to the flat one and
> >connecting the round (signal?) pin to the - side (distr. side). . Now it
> >worked.
> >This is NOT according to the electrical diagram. Something is wrong.
> >Tell me electrical Wizard !
> >What is the principle of this rev. counters??
>
> Smiths tachs use a built in current transformer to trigger the internal
> electrics. This is why the rev counter is shown in series with the coil
> + feed , bewteen the ignition sw and the coil. The wire induces a current
> into the transformer when the points close, then and internal amplifier
> kicks a small voltage on the transformer output, into a larger voltage,
> which in turn drives another pulse timing circuit.
>
> If you have put the tach in parallell across the ignition to coil feed
> wire,
> and it works, then you probably have an electronic ignition on your
> car instead of points huh?
>
> When the tack doesnt work right with electronic ignition, most people
> double wind the wire around the cuurent transformer, to keep the
> transformer from saturating due to the much higher dwell.
>
> If my guess is right, the reason your setup works, is becuase
> putting the tach across the tach feed wire, has reduced the current
> going through the tachs transformer by about a factor of 2, which
> will have the same effect as doubling the tansformers turns.
>
>
> Hope this helps.
>
>
> Jarrid Gross
>
>
It is not that easy
I have no electronic ignition (I wish I had), just the old fashion way.
But there are no way I can connect the rev. counter in series because no
voltage is going through the rev. counter. (from the flat connector to the
round pin connector). The engine donīt start because there are no voltage
to the coil.
Some other electrical rev counters have the wire going one turn around (a
transformer) outside (or inside) on the back of the rev counter. But looking
inside this rev counters, there are only tiny wires, clearly only made to
take very weak current.
Are we talking about different electrical rev counters??.
To me it it looks like the rev counter need current to make it work and
signals from the coil to the rev counter brain so it knows where to point
the needle.
If I do like that, it works.
Kristian Jonsson
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