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Old 23rd January 2009, 09:32 PM   #11
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I added a ground / earth as you recommended. The vibration is now much much less; however, the pedal (remember this is about 18KOhm compared to the inbuilt potentiometer which is 10KOhm) still does not work at all. I am sure I used the correct terminals. In fact I checked again with a digital meter the tip and ring of the plug: the meter shows 18.4K when pedal is up and 0.00K when completely down. It should work at least for half the excursion of the pedal! I am baffled...
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Old 23rd January 2009, 09:47 PM   #12
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check if it is any resistance between sleeve > tip or sleeve > ring. If that´s the case, open the pedal and disconnect it there to keep the shield.
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Old 23rd January 2009, 10:17 PM   #13
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It should just work.

The arrangement in the keyboard (only 2 connections to the pot) is ugly although not uncommon in audio. Are you sure that this is really the case? I always take the wiper to one end of the track if I want a simple variable resistor rather than a potential divider.

Disregarding that, put a DVM across the wires from the pedal and pick 2 that give you a variable resistance in the sense (rising or falling) that you want. Arrange the connections to switch in this pair instead of the pot. As you say it should work for half the excursion at least, so check, once you have it connected, that you can see the variation in resistance at the point that you broke into the circuit.

w
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Old 23rd January 2009, 10:21 PM   #14
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Sleeve - Ring = constant 18K
Sleeve - Tip = variable resistance in the reverse as for ring-tip ie max when down; 0 when up.

But the sleeve is just connected to earth. Should it have any effect on the variable resistance between ring and tip?

Should I disconnect the sleeve connection within the pedal? If yes, should I leave the sleeve grounded? If yes, why?
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Old 23rd January 2009, 10:30 PM   #15
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Thanks Wakibaki for your contribution. I did all that before I ventured to do the alterations to make sure I understand how the inbuilt keyboard potentiometer works ie which leads to disconnect and the same for the pedal. That's why I am baffled by the result of what should have been a pretty straight forward simple alteration!
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Old 23rd January 2009, 10:30 PM   #16
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Yes, you should disconnect the sleeve inside the pedal, you may get another voltage inside the circuit when one end of the potentiometer is grounded by the shield...

You should leave the sleeve grounded to get a proper shielding of the cable to the pedal to avoid noise.
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Old 23rd January 2009, 10:39 PM   #17
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Upon opening the pedal, I notice that the "sleeve" is grounded to the metal base of the pedal armature.

Anyhow, I disconnected that from one terminal of the potentiometer. I checked again and confirmed that there is a variation in resistance between the other two terminals when the pedal is swung down and up. There is no resistance at all now between sleeve and ring and sleeve and tip (ofcourse).

The virtual organ still shows some vibration in the virtual pedal despite all these alterations.

Amazing isn't it!
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Old 23rd January 2009, 10:42 PM   #18
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Silly question: is the cable to the pedal shielded or just three pole???


By the way, put a 20 K resistor in paralell on tip and ring as well, you will get another resistance curve on the pedal but it will get correct resistance
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Old 23rd January 2009, 10:44 PM   #19
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Ok, the sleeve is connected to one end of the pot's track, the ring to the other. The tip is connected to the wiper.

The connections you want to switch in are the tip+the ring or the tip+the sleeve. Just pick one or the other. Forget about hum until you get the basic function. If the pedal works upside-down you can swap the sleeve for the ring.

Connections on a switching stereo socket can be confusing. Plug a (preferrably unwired) jack into the socket and use a DVM to make sure the connections work the way you think they do, by checking that there is continuity between the bare connection on the jack plug and the point where you broke into the circuit.

Finally plug the pedal in and again make sure that there is a variable resistance connected to the circuit.

It should just work. If it doesn't it's because the connections are wrong, even if you think that they are right. It's common for people to look at incorrect wiring they have done themselves dozens of times and not SEE the fault. It's just a human nature thing.

w
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Old 23rd January 2009, 10:55 PM   #20
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You posted again before me, but you should be able to sort it out from what I have written. The grounding is just a red herring if the circuit doesn't work at all.

w
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