From jlcason@yahoo.com Sat Jan 25 06:06:09 2014
Subject:Re: Vent vs burn a question for users

I spent 25 years servicing Hammond's (and other brands). The G-G signal is way too hot for direct feeding the Vent (or Burn). The resistor and capacitor network shown in the link seem reversed to me - i.e. the high value should be in series with the G terminal, and the low value shunted across in order to get enough loss through the pad.
The early Hammonds were made with balanced output because it was not uncommon to feed a dozen tone cabinets in large churches, with hundreds of feet of cable going to them. Same principle as modern balanced circuitry - to reduce hum and noise.


The best idea on the page for a person without wiring and soldering skills would be using a passive DI box, with ground lift and 20db pad. The G terminal and ground would go to the input of the DI, then an unbalanced output of the DI box would go to the Vent (or Burn).


Also, IMPORTANT - be very careful in doing the connection - remove all power connection from the B3. Those early 5-pin and 6-pin connections for Hammond ran the 110 volt AC (or 220 volt for non-US units) through the same connector as the signal leads. Either is enough voltage to kill. Later 11-pin Hammond to Leslie connections used a separate AC feed - Electrical code changed to reduce the hazard of power and signal connections in the same cable. Also - if there is a 122 Leslie kit on the Hammond, about 300 volts DC is on one pin of the connector, through the high resistance DC relay used for the Leslie speed.




Connections to the preamp are far enough away from the AC, and the AC (if still original) has a metal cover over it).