Quadibloc
2012-08-01 20:00:23 UTC
Recently, I heard about the tone generator which was used to provide
the Hammond BC with a chorus function.
I was able to get more information about it than some sites present
from the service manual, but as noted on many sites, it doesn't give
the number of teeth on the gear.
This page:
http://www.dairiki.org/HammondWiki/ChorusGenerator
gives information on the detailed description in the patent for the
chorus generator, but it seems to be incompatible with what could have
been used in the production unit, given the description in the service
manual.
Thus, on my web page, at
http://www.quadibloc.com/other/mus03.htm
on the bottom of the page I present a set of possible gear ratios that
would make the chorus unit perform as described.
I make the unusual assumption that the tone wheels in it must have had
(nominally) 192, 96, and 48 teeth, rather than, say, 128, 64, and 32
teeth for two reasons:
to avoid having the driveshafts turning 50% faster than in the regular
tone generator, but instead at about the same speed, and
so that adding or subtracting four teeth from a 96-tooth tonewheel,
for example, allows shifting the frequency about 0.4% either way, this
not being achievable as easily with a 64-tooth tonewheel.
No doubt, though, those who have had the opportunity to examine actual
units would be able to improve on my hypothetical reconstruction.
John Savard
the Hammond BC with a chorus function.
I was able to get more information about it than some sites present
from the service manual, but as noted on many sites, it doesn't give
the number of teeth on the gear.
This page:
http://www.dairiki.org/HammondWiki/ChorusGenerator
gives information on the detailed description in the patent for the
chorus generator, but it seems to be incompatible with what could have
been used in the production unit, given the description in the service
manual.
Thus, on my web page, at
http://www.quadibloc.com/other/mus03.htm
on the bottom of the page I present a set of possible gear ratios that
would make the chorus unit perform as described.
I make the unusual assumption that the tone wheels in it must have had
(nominally) 192, 96, and 48 teeth, rather than, say, 128, 64, and 32
teeth for two reasons:
to avoid having the driveshafts turning 50% faster than in the regular
tone generator, but instead at about the same speed, and
so that adding or subtracting four teeth from a 96-tooth tonewheel,
for example, allows shifting the frequency about 0.4% either way, this
not being achievable as easily with a 64-tooth tonewheel.
No doubt, though, those who have had the opportunity to examine actual
units would be able to improve on my hypothetical reconstruction.
John Savard