EM Theremin - TOKO Coils

Hi Chris,

using an inductor with higher inductance is (IMHO) not the best option in the EM- and Etherwave design because going too low with the oscillators' frequencies may cause too high resonance current problems with the antenna linearization coils.

That's why I suggest doing the same as Moog does in newer circuit variants: Replacing the variable 100uH inductor by a fixed 47uH inductor in series with a variable 47uH inductor like the EZ-1017.

Another alternative is using the Coilcraft SLOT10-5 which has also 47uH (always in series with a fixed 47uH inductor), but since the DC resistance is different (which is crucial for these differential pair oscillators), some resistors in the surrounding circuitry must also be replaced in order to stabilize the oscillators' working points:

R2, R6 and R16: 1.5k instead of 2.2k
R15, R19: 330 instead of 470

Hello Thierry

many thanks for the info, have sent your suggestion to one of our customers who was awaiting completion of his order for EZ-1015s, which we cannot find in our warehouse.  He has accepted the suggestion so it will be sent off.  Will be using this again as a replacement.   Sorry did not get back to you sooner, many thanks for your advice and assistance it is greatly appreciated.

Best wishes

Chris (Quibis)

Chris, you are welcome.

Don't hesitate to post your further questions here! :-)

Hello Thierry,

thought I would ask you direct for a possible alternative to the EZ-1017 which we have now come to the end of.  You will recall you suggested this would be suitable to use in place of the EZ-1015, which has been used by many people in conjunction with the FL4-47u, which they have obviously found to be OK.  Now, as I say we have no more EZ-1017.  Are you aware of any alternatives to this part.  We are still having many requests for this part in the making of a Theremin, and currently one person is awaiting a suggestion, so help you can help.  Take this opportunity to wish you and all in Theremin World a happy Christmas and healthy 2014.

Look forward to hearing from you if you have any suggestions.

Many thanks

Best wishes

Quibis

Hello quibis,

there is another substitute for these coils, but these require at the same time the change of some resistor values around the oscillators. Moog switched their Etherwave theremins already 5 years ago for the same reason, because the TOKO inductors were not longer available. I will post here a detailed replacement chart with part numbers and component values during the upcoming Xmas holidays, being actually still overburdened by my day job.

Hi Thierry,

Yust wondering whether, when doing the above chart, you could have a look at the 42IF106 IFT -

I have used these extensively in all sorts of oscillators (including modified EW Osillators) and can get various inductances by choosing tappings - I just wonder if these could be a drop-in replacement on the EW.

My tests indicate an adjustable AL from about 23 to 43 for these parts, pins 2-3 have 50 turns, so one gets adjustment from 57.5uH to 107.5uH across these - one  can add in the winding 4-6 (add 27 turns) to get 77uH to 136uH etc..

I often use two of these parts in either series or parallel, to have one as a course adjustment, and the other for fine adjustment.

These parts may be entirely unsuitable for reliable EW operation of course - Which is why I am asking the expert!

;-)

Fred.

 (just an aside - the data sheet specifies 455kHz and 180pF etc - this is only really relevant I think for its use as a 455kHz IFT ) - The 42IF106 is not fitted with any capacitor, and my measurements above used a 200kHz test frequency ( I derived AL, calculated expected inductances, and spot checked the calculations against measurments) - There is some (minor) variation in inductance concequential to frequency, but this is true for all inductors - I have found these parts are fine when I use them between 100kHz and about 1MHz - Above 1MHz (an area I rarely go except when creating harmonic filters) I use other parts.

Chris, you are welcome.

Don't hesitate to post your further questions here! :-)

Hello Theirry.

without seeming to be a pain have you had any time for the EZ-1017 substitute, we have just had 2 enquiries for the Theremin project but as no EZ-1017s cannot help any more.   Any assistance you can offer would be appreciated, I just wonder if I have been looking in the right place for your answer, just looked in the place where I posted the original query.

Best wishes

Chris for Quibis/JAB

Sorry, totally forgot about that. Will write back soon. It's not so easy because using every other coil type will require some other mods in the circuit.

Sorry, totally forgot about that. Will write back soon. It's not so easy because using every other coil type will require some other mods in the circuit.

Hello Thierry,

no problem, but I have kept looking for any answer and your page 4 seems permanently down, so not sure if you have posted a reply.  If you are having problems could you send direct to me at wagtails@blueyonder.co.uk.

Many thanks I will come back to see again if page 4 is showing.

Best wishes

Chris for Quibis/JAB

<dummy post> but you can now get to page 4 where theres another "dummy" post.