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This writeup was graciously provided by HarveyOlsen:

Electro Music (and later CBS) did not provide factory kits to connect so-called "universal" or general-purpose Leslies to Hammond console organs without internal speaker systems. This was done to protect Hammond dealers who, at the time were responsible for most of Leslie's sales. Any music dealer could sell 147s and other general-purpose Leslies, but only Hammond dealers sold Hammond-type Leslies like the 21H, 22H, and 122. However, the 147 hookup is relatively simple and re­quires only minimal technical expertise.

This hook-up is intended for Hammond tonewheel consoles with

  1. Balanced (a.k.a. push-pull or G-G) outputs
  2. A self-powered preamp (with a power transformer and 6X5 or 6X4 rectifier tube)
  3. No built-in power amplifier and speakers

Except for the ?D-100 series (which is essentially a Model ?RT-3 with the components from a PR-40 tone cabinet installed in the organ), Hammond console organs with built-in power amplifiers like the A-100 series can drive 147-type Leslies directly from the speaker outputs. In this case, one of several standard Leslie connector kits can be used and a custom hookup is not required.

Included Hammond models are: B2, B3, C2, C3, D-100 Series, RT-2, and RT-3. Early Hammond models like the A, BC, CV, D, RT, etc. are not self-powered and require DC (B+) from a Hammond tone cabinet or Hammond-type Leslie to power the preamp. "Non-Hammond" Leslies have no provision to supply this power but can be used with early consoles if a separate DC source is provided.

Included Leslie models are: 31W, 44W, 45, 46W, 47, 47R, 145, 145A, 147, 147V, 147RV, 245, 247, 247RV, 147A, and 147A-T. (Models 25, 125, and 225 with power amps are electrically compatible but don't have rotary treble horns and are not recommended for console organs.)

NOTE: Do not rewire the organ's stock 5-pin tone cabinet socket for 147-type Leslies or use a 5-to-6 pin Hammond cable for this purpose! Doing so could result in a serious electrical hazard. Universal-type Leslies require a separate 6-pin socket, which should be labeled "147" or similar. Caution users not to use this socket for Hammond tone cabinets or Hammond-type Leslies. If the organ is also equipped with an 8000 or similar Hammond-type connector kit, be sure that the signal feed is kept separate from the 147 hookup. 147-type Leslie models have no provision to isolate the DC control voltage used in Hammond-type hookups.

For temporary use, it's possible to remove the six-pin plug from a six conductor Leslie cable and make the following connections directly to the organ's preamp. However, this type of hook-up should not be used for portable or permanent use. The installation will be neater and safer if the six-pin socket is installed in the organ's outlet box.

 1   Black   Signal Ground   Connect to the preamp chassis or preamp ground terminal. (This is the brown wire next to the two "G-G" terminals on later preamps.) 
 2   Yellow   Tremolo Relay Coil   Connect a SPST switch between pins 2 & 3 to control the rotor motors. (This sends mains voltage to the AC relay coil.) 
 3   Blue   120 VAC.   Connect pin 3 to the blue AC input terminal on the organ preamp chassis. 
 4   Gray   120 VAC.   Connect pin 4 to the gray AC input terminal on the organ preamp chassis. 
 5   Brown   Tremolo Relay Coil   Connect pin 5 to pin 4. (This completes the circuit to the relay coil.) 
 6   Red   Signal Input   Connect pin 6 to either the red or black "G" terminal (but not both!). 

Set the LoadSwitch in the Leslie power amp to the "open" position. This completes the hook-up. If a 122-type "half-moon" switch is used, it will work backwards with 147-type Leslies. To fix the problem, simply rewire the switch using the previously unused set of terminals. (The same switches were used for both 122 and 147 type kits and have two sets of contacts.)

If a Hammond tone cabinet or second Leslie is part of the installation, they must be "in phase." Two organ speakers close together will have a noticeably uneven pedal response if the bass speakers are out of phase. Should this happen, move the signal connection from pin 6 to the other "G" terminal.

147-type Leslies are easily added to existing Hammond-Leslie installation with a few precautions. There is plenty of signal available but the console's AC wiring can supply power for only two tone cabinets. If a third speaker is used, a power relay should be used to reduce the electrical load on the organ. Also, the life of the organ's "run" switch is extended if the current load is reduced.

Universal-type Leslies should be connected directly the organ preamp. If the organ has echo or other signal switching, these should be bypassed. Hammond consoles were usually used only with external cabinets with balanced inputs. It's possible to devise a switching system for both balanced and unbalanced in­puts but the circuit is more complex and beyond the scope of this project.


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