Topica Loopframe_Guzzi Archive
 

Subject: RE: Diodes and loop Tachs

Author: Christopher Mitchell

Date: Jul 9, 2002, 6:46 PM

Post ID: 1710575084

Yeah the joke was in reference to a certain person who has scoffed at
upgrading old bikes. If I didn't love the old stuff I wouldn't be on this
list (last loop was made right around the time I was born), but I am all for
adding modern comforts to old bikes.

As for vaccum tubes, I run 2 in my guitar preamp. Not everything gets better
when it is modernized.

Learning the difference between reply and reply all,
Chris M.
'71 ambo


 From: Jesse Open <Beaver-@comcast.net>
Reply-To: Loopfram-@topica.com
To: Loopfram-@topica.com
Subject: RE: Diodes and loop Tachs
Date: Wed, 10 Jul 2002 01:32:25 +0000

The original diodes WERE vacuum tubes ! THEN came the TRIODES
,TETRODES, PENTODES etc.
Here in Meechagin we still use vac tubes too ! :))
Christopher Mitchell wrote:
 

Diodes? (cue old kansas biker voice) back in my dad we didn't use
diodes.
Hollow vacum tubes were all the rage....

Example o' cool tach:
http://home.att.net/~ejboehm/tach/tach.htm

example o' super cool paint - no stripes (sorry mom)
http://cgi.ebay.com/ebaymotors/ws/ebayISAPI.dll?ViewItem&item=1842190498&indexURL=1&photoDisplayType=2#ebaylargephotohosting
 

polish wheels? we ain't polishing no stinking wheels...

lates,
Chris


 From: David Washburn <guzzi-@aol.com>
Reply-To: Loopfram-@topica.com
To: Loopfram-@topica.com
Subject: Diodes and loop Tachs
Date: Mon, 8 Jul 2002 21:35:50 +0000

Those of you who are on the MGCL will note that I am still trying to
get
 
 my Tach to work with dual coils and a Dyna.

Here is a synopsis:

My Eldorado/SP has been running cheerfully along as I attack its few
remaining gremlins. I got a working Tach from Mark at Moto Guzzi
classics and closely followed the instructions of Mr. Wayne Orwig. When
attached to one coil it reads half the correct RPM. I made a clever
little "Y" harness with two diodes and attached it to both coils but
the
 
 resistance in the diodes seems to defeat the signal. I do not wish to
fry my Dyna, should I try diodes with less resistance or perhaps
someone
 
 has another idea?


Oh ho! I think I get it now. The negative pole of the coil is always
grounded until that contact is broken via points or Dyna box. Power is
not going from the coil to the tach to make a signal it is the other
way
 
 around. The tach must produce a low voltage which is sent to the coil
(ground). When this is interrupted by the points or dyna that is the
signal read by the tach.


Carl Allison suggested that the signal from one coil might be "masking"
the signal from the other.

Any suggestions?

David




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