Idea with old Hammond

[PermO]

Hooked up my Fluke115 in the loop with the LED and it stays at 0.000A

Yes there is other stuff running on the Arduino, also a 8seg display (i2c) I will remove the other outputs and see what happens.
I thought the pot I put over the clickfiltercoil was messing up my output but that was not the case... So I know why they don't trigger now, but why the level drop ?

Finish my coffee first...

 

[PermO]

I removed all the triggers from the generator, used an alligatorclip to connect a pickup to the output terminal... still got that level drop
Switched preamp just to be sure... nope still level is gone

Checked all the output wiring, nothing changed, all still good.

Weird...

Hooked up the pre-amp to a pickup directly,.... BWOOOOO meters in the red, oh wow !
Something's off in the "output section" of the generator...

So I decided to meassure that Allen Bradley resistor again... wut ? 6 Ohms .. it used to be 20.6 Ohms before I touched it.
So that stupid resistor got some heat from soldering some wires and it went down the drain.

So that's the level problem,...

Great, removed all my work to find out it's that bloody resistor... good to know what value it was I will replace it now.

 

[dmp]

I think it is 27 ohm on the schematic

 

[PermO]

Red Red Black... 22R in this case.

But that was not the problem... again.
Once I took it out it still measured 21.6R ... replaced it anyway.

Doing some more investigation I now find my primary on the matching transformer only measures 0.1 Ohm now and it used to be 4 Ohms...
Bypassing the transformer now increases the level, where the transformer used to increase the output level.

Something must have happened when putting it in the case maybe... last time it played good was before it went into the case.


Still more to investigate

 

[PermO]

Yup,... transformer.

Primary that was 4 Ohms went to 0 Ohms, took it out, measured it... zero, wiggled the wires, nothing, no physical damage nothing has moved or broken. It was mounted sturdy to the metal framework.

Beats me

Found something in my drawer wich seemed to have a good turns ratio, hooked it up and voila,.. the big bad bass is back again.
Now that I have the trigger board removed I will desk check all the SRR's with a tonegen and a 5V psu one by one before I hook it back up.

 

[PermO]

actually... need a relay on each note for each of the 9 busbars I think


This would be limited to one note, monophonic, I think. Each busbar needs a seperate switch (or relay) on each note. The bass only has one busbar though so it works for that.

So for the upper+lower on the M3: 719 for the L100: 654 (since it has 2 less drawbars on the lower)
The wiring chart shows for each note which tone wheels should be turned on for each busbar. The number of relays is the number of boxes.
Would be good to have a better routing solution. Maybe FET as switches?

Since the switching logic is simple (index each busbar freq# +1 for each higher note) should be able to make this controllable with less controls from the Arduino than the number of relays / switches

Now I do, yes, you are right.

You can't bus all fundamentals and 16th and.... because the tonewheel that is the fundamental for one note acts as a harmonic for another note, so yes also these positions need to be switched.

That's a lot of relays.

Still.... somebody should do this

 

[PermO]

So I spend today checking double checking everyting.. but still no succes.

It's the Arduino, it will not put out sufficient current for some reason, only connected the triggers but no succes, it has proper 9V power, nothing is shorting out, it puts out 5V for every note..

I know the SSR's are all good, tested every one of them, they are all fine and all connections are correct.

I see only one solution now and that is adding fet's or transistors to the Arduino digital outputs, I don't mind doing that, there allready is a 5V regulated PSU in the unit and there is an empty perf board at the back of the frontpanel, and I probably have the transistors or fets in my drawer.

So still not there yet, but very close...

 

[PermO]

Just keep going...

I found that I had enough BC547 in my drawer for 13 triggers so I did a little test setup;

And now I have a decent trigger current.

470R as base resistor

330R as load resistor

5V psu

So next weekend I'll do a circuitboard with 13 of these and some connectors and stuff to make it all happen.



(EDIT)

Slight change of plan.... this will not work as I have a cable with 13 positives and 1 common ground.
So I put the load on the Emitter side, no base resistor needed.
The slight voltage drop should not be a problem with my 330R load resistors at the SRR's.
This way I can connect the 13 positives to a transistor with a shared ground.

So yeah "just use a transistor"

 

[Scodiddly]

Super cool!

One interesting thing about the Hammond tone generator is that there's something in the whole mix called "loudness robbing", or something like that. Been a while since I read the service manual. But essentially it limits the total output from any one wheel, aka any harmonic. That's because if you have one particular wheel showing up on several notes (fundamental on one, harmonics on others) it would tend to add up too much and be too loud compared to the others. So there's some current limiting going on to prevent that. Since you're basically just replacing a lot of switching it should be fine, other than that thing about having nine switches in every key.

 

[Tubetec]

Do not discount the usefulness of the drawbars , incorporate them if you can , Ive seen the them used as modulation or swirl with the left hand while the player fingers the notes with the right , you can fade in the low end growl after the attack of the note is over or add a nice swell to a tone that begun as a simple sine .

Theres clip of Daniel Lanois with his buddy playing a moog Taurus with an organists pedal board by hand , I cant find it now .

I had an opportunity to get a chainsaw to a tonewheel Hammond once , Im really sorry I didnt amputate the rotor /keyboard before it was slung into the dump pile, wasnt a drawbar model either ,still though .

For a period after Hammond went solid state the tone wheel assembly remained , the entire lower enclosed section of these models ,which contains PSU and speaker amp /speakers can be got rid of and the appropriate tube pre-amp section could be put in place .

 

[PermO]

I'll stop at the 13 bases ... as far as building goes.

I don't mind theorizing further how this setup would look like.
That would need a pre made circuit board, with smd components allready done in the factory, you really don't want to hand solder that.

That approach might take it in the "do-able" range.

 

[Tubetec]

Pucho posted a great tribute to the Hammond organ a while back ,the real die hards had their instruments shifted upstairs-downstairs they whole lives ,bringing it down to the rotor and keyboard could mean its only a two man job instead of at least four

 

[Lee_M]

This is a really interesting project, it's giving me some crazy and dangerous ideas for my Hammond L100.

 

[PermO]

Now with the 13 transistors,... it's working.

Defenitely need the clickfiltercoil as switching with the SSR's is rather clicky, the are really fast.
So yeah, the fat lady plays the bass...

One thing though,

The fat lady get's rather hot doing that, too hot... the generator is not heavy to drive, I can turn the shaft between two fingers easyly...
This motor has always been running rather hot so I'll have to take a closer look at it.

The switching is fine, but same thing happens on a synth osc. without an envelope, you'll get a click, the coil surpresses the clicks, but it's not 100% sufficient in doing that.

 

[Garagescience]

Gotta say, if nothing else, you could very carefully circuit bend this like Doug Grindstaff did for Star Trek TOS. Heck, somebody might even employ you for it!

https://www.nytimes.com/2018/08/03/...indstaff-star-trek-sound-whiz-dies-at-87.html

 

[PermO]

 

[scott2000]

A like doesn't do justice. Was thinking the Jack Nicholson nodding gif but the scene it's from doesn't fit....
Very cool..

 

[PermO]

Thanks !

 

[Lee_M]

The transformer in the vibrato amp looks like this;
View attachment 91495
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.

That's the "saturable reactor", it's kinda like 3 individual transformers mounted together as a single unit, with all of their secondaries(?) wired in series. They're labelled SR101, SR102, and SR103 on the schematic, their primary(?) windings each form an interesting feedback circuit around parts of V2 and V3 to create the Hammond's vibrato/chorus effect.

http://captain-foldback.com/Hammond_sub/schematics/L100_early.gif
Here's an interesting project that uses them for a "true pitch shifting vibrato".

https://sluckeyamps.com/warbler/warbler.htm

 

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