Hammond delay thingie (was: mysterious delay lines)

[Robert Schrum]

Interesting theory, but...

Look at http://theatreorgans.com/hammond/faq/hammond-faq.html#SEC6 for a quick
explanation of the vibrato scanner,
http://theatreorgans.com/hammond/faq/files/schematics/b3sch-a.pdf for the
schematic of the whole B3 with particular detail on the scanner.


-----Original Message-----
From: "R.G. Keen" <keen at austin.ibm.com> at hcinternet-server
Sent: Tuesday, August 04, 1998 12:38 PM
To: Hcabnivek at aol.com at HCINTERNET-SERVER
Cc: synth-diy at mailhost.bpa.nl at HCINTERNET-SERVER;
keen at keen.austin.ibm.com at HCINTERNET-SERVER
Subject: RE: Hammond delay thingie (was: mysterious delay lines)


>Speaking of delay like devices  (though I'm not sure this real is one) can
>someone explain how the small motor driven drum inside a Hammond organ that
>has all the wires connected to it works to generate tremolo/varabrato.  I'm
>not talking about a Leslie here, this thing has a wire from each of the draw
>bars connected to it I guess a single output wire, and some rotating part
>inside that's turned by a belt running off the same motor that turns the tone
>wheels.
Sounds like an oil can delay. These work by having an insulating layer
inside the rotating can and a high voltage signal source which deposits
charge on the inside of the insulating surface, somewhat like the
charge depositer in a Van de Graff generator. The charge then rotates
with the can and is picked off some rotational delay later by a (very!)
high impedance input. The oil inside is to keep the charge from
bleeding off into the air inside the can.