Leslie Speaker Pre-amp Schematic

[Joe Hart]

I have a Leslie 147 speaker cab, and to run a guitar through it, you need something called a Leslie Combo Pre-amp Connector Kit #7875. They have been discontinued, but original units pop up occasionally for about $150, but they are noisy and somewhat unreliable (I've been told). A new company makes a unit that will work, but it's around $350.

I have a schematic for the original ones here:
www.joestump.com/eBay/LesliePreAmpSchematic.JPG

This may be interesting even for non-Leslie applications (or maybe not).

My question is: how hard does this look to build? I have done some house wiring (light switches, dishwasher, etc..) and have built some 9v pedals. Is this way out of my league, or not too bad? I just don't want to build it, plug it in and toast my Leslie or burn the house down or get electrocuted.

I have been told that some Japanese company makes a DIY kit for this item, but I can't find it.

So, any help would be VERY much appreciated. Thanks.
-Joe Hart

[Dan N]

You might not want to get lost in "Leslie Preamp World". The amp in there is just a power amp.

Does your guitar amp have a preamp out or effects loop? Plug it into your leslie and see what happens. Plug in an LPB-1. Plug in the out from a mixer.

Worth a try?

[Joe Hart]

The problem is that the Leslie has a crazy 6-pin jack. This is how it gets current as well as the signal - sort of all with one cord. I would love to find a way to just run any old preamp into it, but there is no plain old input jack (like a 1/4" or RCA's). Then I could use my actual "sound" instead of just whatever the preamp produces.

Anyone?

-Joe Hart

[petemoore]

If your not familiar with working with high voltages, read of the dangers and precautions first...how to 'empty' caps etc.
 Then...First thing I;d do is figure out where the power supply and ground are with the DMM, checking for Voltage. These will show the highest voltages...
 Probly high voltage dangers in there...watch out for those...
 Unplug the multi-connector, start with the no power side, see if you can figure out which wire goes to a source, and trace that to the pin/socket lug. Make a map. Same with output. Use process of elimination and study the map.
 Without seeing the unit, all I can recommend besides be careful is this^...
 actually I can't recommend it, but it worked for me before I thought I knew what I was doing. With the thing all hooked up...and at your own risk...
 Take an insulated screwdriver, with your hand touching only the *insulated part, and touch some of the the NON Power Supply wires with it, carefully>one at a time...you might be able to hear a click or better at the outputs and a little stronger input buzz at the input.
 If you get this far, sorting out Left and right should be N/P.
 If this doesn't work, hook up an 'audio injector' for a source of inputm and to ground to use to isolate the wiring order. Use the output from a  kiddie keyboard with a note taped down through an *insulated probe.

[Lonestarjohnny]

Joe, first off you need the preamp and a foot controller, all that will do is run the motor's or motor, i did not look at the schematic, i have several leslie cab's and they all wire differently, but the hammond site has all that info and the proper wire'ing schematic for which ever cable your useing, some of mine are 11 pin, 9 pin, a trickey one to wire out, because they used 3 or 4 different wireing schematic's on that 1, and 6 pin, you get your foot controller and amp wired where you can control the speed of the leslie with your foot controller and then you can feed any amp speaker out put jack straight to the speaker's, just make sure the amp is compatible with whatever ohmage your speaker cab is designed for, 8 ohm, is normal on the smaller cab's.
just go check through the Hammond site, it has all the info you need to wire it where it's useble for guitar, also check out the Fender Vibratone cab, you'll get some idea's from reading about it also.
JD

[Lonestarjohnny]

http://theatreorgans.com/hammond/faq/hammond-faq.html#SEC27

This will help you out a bunch, and if you do decide to use the Hammond amp it's only rated at 40 watt's.

Johnny

[Joe Hart]

Thanks for all the help! But I don't want to put the horse before the cart. Is the schematic buildable by a novice? Are the transistors still avaliable? Or are there suitable subs that anyone knows of? What about the price of the parts? Will this run me too much? How about the transformer (I think that's what it is) on the schematic? Is this a standard type one or will I have to have it specially made (and therefore probably too much money as compared to already built units)? Thanks!!
-Joe Hart
P.S. I did find the previously offered info very helpful!!

[Lonestarjohnny]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=64430&item=3739367327&rd=1&ssPageName=WDVW
Check this out Joe
Johnny

[Lonestarjohnny]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=64430&item=3739605873&rd=1&ssPageName=WDVW
and another,
Johnny