All those inquiring about the Germanium Transistors used in the Smiths
electronic tach, please see the tech tips by Tom & Mark for more
information.
http://www.corpdemo.com/tiger/techtips/tbtach.html
http://www.corpdemo.com/tiger/techtips/motach.html
According to the tech tips, these transistors can cause erratic readings due
to their age. I was able to repair and calibrate all my tachs but one, I'm
guessing that one of the transistors is bad causing the tach to jump around
and not give a steady reading. I was able to fix my other spare tachs by
replacing the .25uF caps the 6V Zener diode. I used parts from my local
Radio Shack, they did not have the exact part but I used the next best
thing. In place of the .25uF cap I used a .22uF (close enough according to
Mark) and instead of a 6V Zener diode I used a 6.2V Zener. I was able to
calibrate them using a signal generator and a scope. I tried to get in touch
with Mark to find out about his computer based calibrator but have not been
able to get a response from him. Since I plan to keep my car for a little
while longer, I'd like to have a few extra parts for repairs just in case
these parts become extinct.
Sergio
1967 Sunbeam Alpine
Series V 'AJNT 86'
still working on it but getting closer!
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 10:44:16 CDT