Connecting a Leslie to a Hammond H-382

The Hammond H has a built-in connector for an external speaker and includes controls for main/echo/main+echo on the front panel. In Hammond/Leslie lingo these terms are defined as follows:

Main: activates the built-in speakers (this is the default when no external speaker is attached). There is a little switch next to the connector at the back that enables/disables the external connector feature all together…

Echo: activates the external speaker and disables the internal ones

Main+Echo: Well you’ve guest it… It activates both internal and external speakers

As I’ve written about before, my Hammond’s main/echo switches behavior has been hacked. On my Hammond the switches controls the reverb. I’ll eventually look it to that and rewire the switches to the stock behavior. I do not know if this was common or a factory mod at the time. If you do have a H Hammond and could confirm this, let me know.

The picture above shows the connector (7 pin – well 5 if you don’t count the 2 guides) and the switch that activates the connector and front panel switches.

Below are the schematics for the related circuit (click on the images to make them clearer). In the first schematic you will see the connector P304… which is our external speaker connector.

Hammond connector pins detail

Pin# function
1 Channel A output
2 Nothing
3 AC
4 Ground
5 AC
6 Nothing
7 Channel B output

Before you go further you will need to define the type of Leslie you have. Careful if you don’t use the right wiring you will blow things up.

By default, the H series Hammond is meant to be used with a special Leslie that has 2 channels + bass… model 205 or610. If that is what you have you will have to use a 008030A kit. You can find the documentation for the kit on the internet. Just install the kit between the Leslie (9pin) and the Hammond connector at the back of the organ, flip the black switch on the back and the main/echo tabs on the front of the organ. Enjoy. I’ve never tried a 610, so I have no idea how it sound, but given that it is stereo and has a bass speaker and uses 8 X 7189 tubes… It’s probably very loud.

(note: you should look for the excellent Leslie Speaker Description Chart, compiled by Harvey Olsen for details on the various Leslie models)

If you have a 122/142 Leslie (type 6H), which means the Leslie uses a balanced input, you will need to use a  008216 or 008240A or 024216 kit (they seem to be equivalent), you can find one on eBay or on the web. This sums both channels (from stereo to mono) and has a volume and tone control. I have not used this kit (I just used the metal box and plugs from the one I ordered) so I do not know how it sounds. I’ve read on the web that the vibrato/chorus circuit does not sound good when summed to mono.

In my case, I have a 225 Leslie which is in the 125/147/145 family (type 6W), this type of Leslie has an unbalanced output. So I just routed the wires as needed, using the diagram below. I only wired channel A instead of summing both channels, as I read that the vib/chorus sounds better this way.

Leslie 6W pins detail

Pin# function
1 Ground
2 Fast/Slow Switch – Pin1
3 AC + Fast/slow Switch – Pin2
4 AC2
5 AC2
6 Signal – Chan A or Chan B
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Leslie 225 amp rebuild

As posted previously my Leslie amp needed a cap Job.

Because I had some suitable axial caps in stock, I decided to use them instead spending the 30-40$ to get a suitable replacement can cap.

While I was in there, I decided to rewire the whole amp using boards as done in guitar amps, as I find this easier to maintain and troubleshoot than point to point wiring. My Leslie is not collectible, thus no need to be concerned about keeping it original.

I replaced all parts for the amp including the tube sockets, the rectifier diodes, etc… I kept a couple coupling caps that tested in spec, as well, as the parts for the relay (fast/slow control). I removed the 8 Ohms load resistor, because I never plan to  connect my Leslie to a speaker output. I rewired the amps with a star ground.

The voltages where a bit high compared to the schematic , so I increased the first dropping resistor to 100 Ohms. which brought it closer to the expected value. I ended up using 25 watt resistors for the power supply, because the 10 watts ones were getting hot. ( I changed them after I took the photo!)

To reduce noise, I raised the filament heaters above ground using 2 X 100 ohms resistors (on on each side of the power transformer white wires).

I also added 1K grid resistors for the output tubes, from what I’ve read this increases the tubes life by avoiding conditions where the grid is more positive (… don’t quote me on this) than the cathode.

And finally I increased the cathode resistor to 330 ohms (from 250 ohms) because the tubes were red plating with the original value (my voltages are higher!).

Once I was done I tested using a guitar and a connector box I built (more later) and everything works. The amp is now much quieter than it was.

Next step will be adding a top rotor. I have all the parts, just need to cut and install a shelve.


Edit 2014-May-30

Finally did a cap job to my organ this winter and replaced those Tung capacitors… They were all defective… Probably got a bad batch.







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Leslie 225 Amp

I finally cleaned my Leslie motors a couple of weeks ago… I ordered a motor from Ebay for my top rotor project and decided to clean the bottom rotor from my 225 at the same time.

As I had to opened  the Leslie,  I decide to remove the amp to see how it looked. Here is a  picture.

It is a very simple circuit. I have access to the service manual (got it from captain’s foldback site).

Some of the resistors show signs of heating (mainly the wire-wound ones and the big brown one at the bottom of the image). I will replace them at the same time as I replace the electrolytic caps.


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FR2 Rhythm Machine

The rhythm machine in my organ has seen better days. Most of the beats only make a 1/8 hit-hat or snare sound.

From what I was able to gather around the web, it is the same drum machine as the FR-2L from Acetone, which later became Roland. The main difference is the power supply, as the Acetone model has an internal power supply.

The drum machine contains 3 boards. The bigger one is the circuit for the beats (that’s the circuit that has issues in mine). The one at the end with the round chokes is the sound generator. As you would expect, all drum sounds are analog. The smaller board is used to split the mono signal in 3 (left/right and bass).

By using the 1/8 control signal that is produced when most rhythm buttons are selected, I was able to confirm that all sounds work and to listen to them. The trimmer on the sound generator board control the sounds (typically one trimmer per sound). They change the character of the sounds (I’ll record a YouTube video at a later time).

I’ve been searching for a schematic, as I am not familiar with analog rhythm machines. All I was able to find is the Roland TR-77 schematic, which is somewhat related but more complex. I’ll have to study it before I attempt repairing mine.

I performed a cap job, but… it did not solve the problem. Some pictures …

I’ll report progress here…

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Percussion Mod Before and After

Last week, I tackled the task of modifying the percussion of my H-382 circuit to have distinct harmonics (like the B3) instead of combination of harmonics (ex. Banjo :-<).

It was not an easy task… It took me a whole day. I had to disassemble  the back, the top, and the tab panel to gain access to the tabs. I’m very pleased with the result.

I modified the tabs as follows:

Original Now
Chimes 2nd
Glock 4th
Guitar 3d
Marimba fundamental
Xylophone 6th
Banjo 5th

The sequence may seem odd, but I originally wanted to keep as much of the wires where they were. Given that I had to move almost all the wires in the end, I should have just put them in sequential order… Well lesson learned for next time….

I’ll detail the mod (schematics, wires, how to) in a future post.

The next step will be to bring percussion volume and decay to the front of the organ (I’ll probably put potentiometers in a box next to the leslie Fast/Slow control for easy access and to avoid making holes in the panels).

The videos below show the before/after sound. (Please do not be too rough on the production value and playing… I did no post processing)…

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Leslie 225

A couple of weeks ago, I found a cheap Leslie 225 for sale locally. I grabbed it with the intention of trying it with my Hammond H-382, to get the fast/slow spinning sound.

The Leslie 225, is one of the less desirable models… It’s a two-speed (fast/slow) single rotor (a single full band 12″ rotor, instead of a upper horn rotor and 15″ bass rotor). It the Decorator cabinet (which does not easily fit in a car!!!!) of the model 125 that has a standard leslie cabinet and is powered by a 20 watt tube amp (2X6L6).

I plan to connect it to my organ and maybe add an upper rotor to it. Alternatively, I’ve heard that it is a decent speaker to get a Leslie guitar sound… So I’ll also give that a try.

I’ll show you how, I connect a Leslie with a 6W pinout (145, 147, 125, 225, etc) to an Hammond H-Series in a future post.

Pictures of course…

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Oiling the beast

The person that gave me the organ told me that the organ had not been oiled in a while (5+ years). So I shopped around and ordered some Hammond oil from Goff.

I received the oil earlier this week. I Followed the instruction and oiled the 2 small cups on the motor and the 2 white cups on the generator.

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