My name is Noah Benzing and I'm attempting to fabricate a wiring harness for a Hammond tonewheel generator.. it uses 96-wires/pins...
This had been tried before with disastrous results.. using a ribbon cable....
The crosstalk was so bad it rendered the organ unplayable.
How can I eliminate cross talk in a situation such as this? I would like to take someone's failure apart and turn it into a sucess..... enlighten me.
Please e-mail me at:
noahbenzing@gmail.com

 

Running a conductive ground plane, say grounded aluminum foil, very close to the ribbon greatly weakens crosstalk. Try it first with your existing setup.

Supposedly each conductor has an "image" on the other side of the ground plane, like the image in a mirror. The closer the virtual image is to the actual wire the more the fields cancel and so you get ~ no crosstalk.
This was why the 6.3 VAC filament leads for vacuum tubes were pressed against the ferrous metal chasses.

 

It not totally clear from the picture, but it looks like twisted pair wires in the ribbon. If so, are both pairs carrying signal, or is one of the pair a ground? If both carry signals, that would certainly be a source of crosstalk. In that case replace the twisted pair with a ribbon cable with parallel wires. That would greatly reduce crosstalk.

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Carl

 

It will depend on what he's sending and the signals used. Twisted pair cabling is often used to reduce noises in an environment such as this. I work on systems that use this type of cabling for filtering. But, then again, my systems are designed for it's use. But in this installation, it looks like a patch job. Is that right? If that's the case, crutschow would be correct. Try the flat ribbon cable. Is the system pre-wired already (in it's final stage minus the cross-talk issue). Or do you have more work to do?

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Hey guys I really appreciate all the feedback on this project. The picture up above is from someone else's attempt to fabricate a wiring harness for a Hammond tonewheel generator *electronic organ*... there are 96 wires coming out of the generator, each one a different frequency for each key on the organ's manuals. I've thought of using this connector....
[BR]
[BR]
The current harness is a massive bundle of cloth covered wires *you have to remember that this instrument was manufactured in July of 1962*... not like the ribbon cable wires seen in the photo. So I have room to play to avoid his same pitfalls.... which is why I came here.... lol.
The organ in this particular... enthusiast's wiring project is a B3.. the king of Hammond organs. Mine is an L-103.. a much smaller "spinet" model, but uses an almost identical tonewheel generator *spinning phosphor bronze discs next to electromagnetic pick-ups that generate an oscillation that is what we know as the Hammond "sound".
If it would help to see what I'm working with and if you have an open mind.... look at my video near the end and you can see the harness I'm working with going across the brass cover of the tonewheel generator and spreading out so that all 96 wires can connect to terminals that run the entire length of the generator....
Fast forward to 7:13 and watch up to around 8:10

http://www.youtube.com/watch?v=y34478fzY3M

So... looking at what I have to work with and not being in the middle of an imminent failure such as my predecessor... what could I possible do to make a connector that will modularize the tonewheel generator that won't introduce crosstalk?

 

Do the original wires have any shielding, either individually or over the whole bundle?

__________________
Carl

 

A standard practice for crosstalk is to use a ground wire in between each signal wire. So you would have S-G-S-G etc...

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Slowing the signal rise/fall times will also reduce crosstalk.

 

I believe the tone wheel generator rotates at a constant speed, and the frequencies are set.

To slow the rise/fall time would be to alter the frequencies, since they are analogous, thereby altering the sound.

__________________
"Remember, you're special.....just like everyone else."

 

I assume you're referring to flat ribbon cable. It works particularly well with that.

__________________
Carl