Idea with old Hammond

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PermO

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So I've got this this old Hammond L100 tonewheelorgan stinking up my living room for a couple of years now.
I got it for free as it was in a horrible shape, but I managed to get a sound out of it after the first tube preamp, vibrato amp, power amp are all broken.
Keys are falling off, and some notes don't play... I suspect this is the work of a mouse living in the amp section.

It needs to be discarded as it is not worth restoring it.

But there is one thing I absolutely love about this thing..

The bass notes (pedals)

So I had this crazy idea of collecting the tonewheels of the 13 bass notes with the coils and caps that go with them, stick m on an axle and drive them with a smaller size AC motor (by my understanding these all run the same speed as they sync to the mains 50Hz).
Instead of putting the pedals back, use a transistor to switch notes on/off (there's no velocity on a Hammond) and use a Arduino to trigger the transistors from MIDI.
What would result in a MIDI controlled tonewheel bass... I would love that.

Do you think this can be done, or am I missing something ?

It will be thrashed and trashed anyway, I will collect the transformers, speakers and the bits from the tonewheel assembly if this would make sense.
 

Fuzzie

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from the looks of it in this video it is not going to be easy to separate / isolate only the bass tones. But i'll bring a big saw my next vistit to you ;)
 

PermO

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That channel has a lot of info.

Seeing this, yup keep the tonewheel assembly in one piece, clean it up, make it run without the squeeky noises it makes now and take it from there... at some point.

Defenitely going to keep that bit and some goodies I might find and trow the rest of the stinker out.
 

PermO

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Yes,... me, I'm the guy that got it for free to strip it for parts.

A friend of mine bought the Lesly, the deal was he had to take the ugly stinker also, so he called me "do you want a free Hammond ?, it's a small one"
I sayd yes, but it happened to be a big ugly stinker and not a small one at all... It comes apart in two halves so it can be transported, they call it "portable" but you will need 4 guys to lift it.

I had some hope of fixing it, but is really beyond fixing.
It think it has been sitting in a pub for a very long time... the smell ... really, this thing is disgusting.
Some might imagine an organ, this is not it, it's a total wreck, that used to be an organ.

I'm only trowing out the stinking woodwork plywood frame.

I'm going to keep the whole tonewheel assembly as is and mount it on a board.
I'll keep the drivers, the transformers, the pre-amp can, the vibrato amp can, the footpedal, any bits that might come in handy for a DIY project I will keep.
 

PermO

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So, we did it,... the big ugly stinker is gone !

And I am very happy I did, from what I have seen so far it is impossible to service the tonewheel assembly without removing it from the organ, you can drop a bunch of oil in the funnels and say a prayer... but that's about it.
So we took it out in one piece, gave it some basic cleaning, lubricated all the bearings one by one from the underside and started it up.... it runs !

And now after 12+ hours of running it's getting pretty smooth.
Also the tonewheels seem to be in great condition, all of them still have the orange paint on the edges, and this assembly has all brass gears, no nylon. This is a nice unit now, though it's smelly and still sticky, but that will be adressed in the near future. When I shut down the motor, the whole assembly keeps spinning for 5 seconds, I think that is a very good sign !
20220304_103842.jpg
My plan is to put it in a wooden box, with a lid with piano hinges, put some black Tolex on it, IEC connector and a powerswitch and connect the bases to a 15pin connector.
My initial plan of only taking the bass notes (mechanically) would not be a wise thing to do, as all the fundamental tonewheels have the same size, the pitch is done by the gearing system.
So this will be left intact, get some proper cleaning and lubrication and put in a box so it will stay nice and dustfree.

I think this thing has been sitting in a flood or something... this is the state of the poweramp;
20220303_201150.jpg
A friend of mine who does repairs on tube stuff and organs will take it for parts.

The big surprise was this;
20220304_102920.jpg
This organ had no reverb, as in, there was no reverb switch, and I never got a reverb sound from it...
That's a nice spring unit in good condition, I allready have a stereo system running with accutronics units, but a friend of mine would really like to build himself springreverb so he can use this tank.

My friend Fuzzie helped with discarding the nasty bits took the footpedal and switches set and will make that into a MIDI controller.

So yeah, we had some fun, I don't regret it one bit... the big stinker is gone and all the nice bits are finding a good home.
 

Disco Volante

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Great work, looks like you guys had a lot of fun. Keep us posted on the progress;-)
That's a cool little amp, looks like a EL84 PP type thing with a pre-stage and a small input transformer?
I've restored a few amps that spent their lives in bars. It's incredible how much gunk they collect over the years, when smoking was still allowed...
 

PermO

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I'm not sure, it has indeed 2x EL84 ...

I found some schematics that will do, it's not exactly the same organ, mine did not have the flute / trumpet / etc. flippers.
L100_early.gif
The donor was build in 1969, Antwerp, the schematic shows how the pedal section was set up.
I kept all the bits, the click filter coil, the drawbar section and the interstage transformer, plan is to wire up the bass section following the original diagram and hook it up to one of my preamps in my setup and see what happens ?
Hooking up a bass pickup directly to a high z preamp sounds great, it has about the same output as a passive bass guitar.
As I no longer have the pedal section I made a midevil keyboard with the same "action" as the pedal section for testing purposes.
20220305_131104.jpg
I spend 3 days on the floor cleaning the @#$%^%$! out of this thing, and started applying oil into the funnels again after finding all the wicks to be still in place

So I figured out where all my notes are... and hooked them up to the midevil keyboard.
And now I have this;
20220306_212345.jpg
A nice smooth running generator and all the bits to recreate the passive part of the bass section.

To be continued...
 

PermO

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Quick update... it works !

Finding the matching transformer inside the preamp was the key factor to make this work without humm.
I think it also contributes to the sound, bases sound fatter and slightly more crunshy now, compared to taking it directly from the pickup, also the high pitch whining noise that sit slightly on top of the notes when taking the signal directly from the pickups is now gone.

I still have something miswired I think as the drawbar has no effect...

I like this bass (y)
 

PermO

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Still don't understand why that drawbar was not working as it was wired correctly... but never mind, I don't want a drawbar anyway, I just want a good output signal.
So I wired it up like the this and it gives me a nice "hot" output signal with no hum and a very acceptable noise level, now the rest of the organ is detached noise levels are way down.
20220309_105153.jpg
The 20R is a factory selected resistor between 10 - 40 Ohms to match with the tonewheel assembly, I almost trew it out because it's a Allen Bradley resistor 😀 but wisely I decided to look why it was there in the first place... better keep that.
I don't understand how this value can be so low ? ... this seems like almost completely shorting the signal to ground ?
There seems to be quite a ratio on the matching transformer, the primary has only 4 Ohms DC resistance and the secundairy wel over 4K.
In the schematic the secundairy is terminated with a 1M resistor, from my understanding I don't have to put that resistor there as I am running the output into a 600K JFet input on a preamp... so that is my resistor now ?
20220309_100228.jpg
I decided to mount the matching transformer and the clickfilter coil on the tonewheel chassis so I can keep the wiring short.
So now that this all working and sounding nicely, the copperstrip keyboard needs to be replaced by MIDI switching, the idea of doing this originated many years ago, and I allready have the MIDI part.
20220309_081549.jpg
The central scrutenizer holds an Arduino, it takes MIDI (clock) from the DAW and is programmed to put out 5V for C1 to C2 on the MIDI keyboard, so I have 13 pins that put out 5V whenever a note is played, for the duration that the note is played.

Now this will need some interfacing and here I will need some help "just use a transistor" people say, but I think there will be more involved than just "a transistor" so I started looking up some stuff using a transistor as a switch and I found some examples here;

That did not really help at all lol, I see problems there... I'm not trying to switch a LED, I'm trying to switch a tiny low voltage high impedance audio signal and I don't want any DC to end up in that signal.

What would be a good approach for this ?
The Arduino and the tonewheel assembly sit let's say 3 meters apart, I think that will not be a problem for the control voltage so the transistors can be placed right at the tonewheel outputs to keep wiring short, also I hope this can be done without adding another powersupply for the transistors.
 

PermO

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Oh yes !.. Thanks, that had not crossed my mind yet... that could be just perfect !


I'm going to look into that, I think I have one or two left in my parts drawer as I used one on the MIDI input of the Arduino.
 

PermO

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Thanks !

The transformer in the vibrato amp looks like this;
20220309_152013.jpg
I think it's for the heaters, nothing audio... also found 3 6V relais that were probably used to soft start the B+, those are nice parts to have for some tube project.

The funky transformer, yeah that one is funky, if you ever run into one, grab it and hook up a bass with passive pickups like the schematic... you'll be surprised !
I disconnected the generator and hooked up my bass, it sort of sounds the same... I might as well stick it in a box and be done lol 😀

I'll see if I can record a bassline with the medevil keyboard and post it... so we know what we are talking about here.
 

PermO

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So I've been looking into optocouplers and found this;


But,... still, it has the same "problem" it adds the control voltage to the switched signal, can't have that.
I know this can be taken care of with DC blocking caps but that would involve more parts and a little circuit board and a constant 5V powersupply for the optocouplers. I rather not go that route, and I don't want anything potentially affecting the sound of my bass tones.

I had a chat with a friend last night and he came up with a solution.
Miniature 5V signal relais.
He used a bunch of those in a passive remote controlled balanced volumecontrol that does not change impedance when in use. It uses an Arduino to activate a relais matrix that selects a minimal amount of resistors to create 1dB increment stepped, balanced volume control.
They are very fast and it's just a little switch with gold plated contacts that will not alter my sound.
Also it will probably not need any extra parts... in the worst case (if my cable is too long) I can add the switching FET's to power the relais coils.. but I probably won't need that.

I'll do a little test with some larger relais I have sitting here...
 

PermO

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dmp

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Could you use a premade MIDI to relay board like either of these? I would use a relay over a transistor or optocoupler.


Only issue is I only see 8 relay versions. I'm not really clear on how the note activation works. Is there a switch to ground for every note through multiple octaves?
 

dmp

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A lot of helpful info here:

Opposite because this guy is making the organ keyboard a midi controller, and your project is to control the tonewheel with the midi signal. But you just need to do everything in reverse

There are so many bussed type organs and synths that maybe someone makes a premade controller with a bank of relays that just could be wired in? I have a Roland organ / string synth and a hammond M3 I would love add MIDI control to
 

PermO

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That relay switcher would work, only for 8 channels, but it's rather cluncky and rather expensive as a solution...

I'm almost there, got the tonewheel bases sounding good, and I've got 13x 5V gates from my DAW C1 to C2, it's just the final step of the interfacing that needs to be done.

So far I'm on two options, they are both inexpensive and at the same pricepoint;

High sensitivity miniature signal relay;
Maybe these can be driven directly from the Arduino 80mA outputs (with a flyback diode) and with help of a transistor these would defenitely do the job but that would need adding a 5V powersupply also.


Or the solid state relay, these are 10x faster switching and have no mechanical parts with a limited life cycle, the IRED can be driven directly from the Arduino (with a current limiting resistor)... but I don't understand the right side of this schematic, will it behave just like a relay ?
It does not seem to need additional power, just a trigger input, but I may be wrong here.

I'll probably order both and just see what happens.
 

Scodiddly

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Years and years ago, but at one point I had some FET optocouplers, same sort that are used in guitar amps to switch effects loops and such. Good for audio signals.
 
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