>
>Jim, you might be referring to this site which includes some good tach
Check out this link:
http://www.zaks.com/mgb/
(what follows is something I recently to the MGB V-8 list)
This is the right place, follow the "better tach circuit" link.
>From what I understand this information was originally generated
by a TR7-V8 person who did some reverse engineering of the TR7 and
TR8 tachs, which are the same and/or similar circuit as the 'B.
The electronic Smith's tach uses a custom frequency-to-voltage IC,
a rather simple gizmo. This chip is soldered to a "thick film" ceramic
board, which has a resistor (thick black "ink") that has been trimmed to
calibrate the system for a 4 cylinder. By soldering a 100k pot
between pins 4 & 7, you are adding a parallel resistance to the
thick film resistor, and can recalibrate the instrument. Actual
application is not as dreadfully nerdy as my engineer-speak sounds.
I'm sure there are a few places that'll tell you this will destroy
the tach, but then those places want $50 to $75 to solder on a $1
part.
I'm pretty sure *somewhere* I've got a schematic of the Smith's
electronic tach...
-Keith Wheeler
Team Sanctuary http://www.TeamSanctuary.com/
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