Jim,
There is scarcely a project I undertake that, had I known how much work it
was going to be, I would have started. Ah, well; without ignorance where
would I be? What you really need, of course, is to have Theo come over with
his scope and diagnose this problem for you. Since that would involve a
little more of road trip than Theo would likely undertake on short notice,
and seeing as there has been very little first hand advice offered you, I
will do my best to help.
First off, just so I'm clear on what MoMa did, is this still basically a
stock tach, at least so far as using an inductive pickup; that is, the wire
between the distributor and the coil is not physically connected to the
tach. The stock setup has, I believe, has only one loop around the tach
pickup. If this is essentially correct, then you might try wrapping three or
four loops around the inductive pickup loop on the back of the tach. A diode
in series with the distributor-to-coil wire makes some kind of sense all
right; it would keep the current flowing in only one direction. But it seems
the open points already do the same thing. The diodes might also reduce the
current significantly, which wouldn't be good for your tach or the power
output of the coil. Why they had you put two diodes in the circuit I'm not
sure, maybe just one didn't have enough voltage capacity (or current if in
parallel).
So, basically all I can really suggest is you try another couple of loops
around the pickup and call me in the morning.
Hope this helps, otherwise, you can get a Cobra Smiths tach for about $150.
Just paint the needle red and you're good to go. (Not really!! It took me
about three hours of fiddling with inductors and capacitors to get it to
work well.)
Bob
-----Original Message-----
From: owner-tigers@autox.team.net [mailto:owner-tigers@autox.team.net]On
Behalf Of James Pickard
Sent: Sunday, August 12, 2001 8:51 PM
To: Tigers Mailing List
Subject: I give up
I've got a tach rebuilt by MoMa and I'm running a Pertronics ignition. The
Pertronics is great, but the tach only functions properly to 3000 rpm.
Above
that it falls back to zero. I know I'm not the only one on this list with
this problem. I sent the tach back to MoMa, who checked it out, pronounced
it
fine, then forwarded it to Pertronics. Pertronics returned the tach with
two
diodes to add in series to the wire between the tach and the coil. Without
the diodes, the tach works as before (only works to 3000 rpm). With the
diodes, the tach doesn't work at all.
So I give up. I'm tired of screwing with this. Give me some options here.
I
won't go back to points, but I'll change from the Pertronics to something
else. Or I'll change tachs as long as it looks stock. Money isn't an
issue.
What combinations work well?
Jim Pickard
B9473298
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