Noob in action - need help with DIY etherwave

Hello everyone, first all excuse my bad english.
I'm Marzio from italy, i've a passion for DIY and i tried to build the moog EtherWave starting from the original schematic by using my own layout, my layout is divided in four pcb.

unfortunately it does not work, i need some help to understand how to debug this.

At first i found some mistakes in my layout, now i fixed that but nothing changed.

here's the voltages on 2n3904:
Variable pitch oscillator:
Q1 e Q2:
C:11,88v
B:-0.01v
E:-0.67v

fixed pitch oscillator
Q3 e Q4:
C:11,88v
B:-0.01v
E:-0,7v

Q5:
C:11.88v
B e E:6.5v

volume oscillator
Q6:
C:11.88v
B:0v
E:-0.09v (this should be +0.2v!)

Q7:
C:11.88v
B:0v
E:-0.09v (this should be +0.2v!)

Q8:
C:11.88v
B:-2.87v
E:-2.35v

(the reference is the original schematic of moog etherwave pdf)
another critical point i think is the induttance type and position...

i used this kind for the fixed values:
fixed type (http://it.farnell.com/murata-power-solutions/22r106c/induttanza-10-mh/dp/1077043)

and this for the variable one
variable induttance (http://it.farnell.com/toko/5pnr-3509z/coil-variable-5p-series-47uh/dp/1516081?Ntt=variable+inductor)

for the variable induttance i connected pin 1 and 3 look at this datasheet (http://www.mouser.com/catalog/specsheets/XC-600014.pdf)

In the VCO i used a JRC13600 but i also have a LM13700.

i hope you can help me!

Marzio

those fix inductors will not work

something like this is what you want... bourns/miller coils 6300 series (http://www.mouser.com/ProductDetail/Bourns/6306-RC/?qs=sGAEpiMZZMueR%252blcXtRMwX8lj5SnzEMncTsxETOh8z0%3d)


larger with three sections....

or like these (big ones)....

coils (http://www.therealcharleshobbs.com/theremincoils/emwithkit.JPG)

how about the variable inductor?

(double post)

I'd guess that the variables are fine. Ive found the oscillators to be pretty forgiving as long as they have the correct inductance ranges.

lm13600 and 13700 are the same (more or less) and both will work.

The voltages that you posted show that the oscillators are most probably not working. But a voltmeter is not sufficient for this kind of work, you need an oscilloscope and a precision frequency counter.

It may be that you did not correctly identify the pins of the variable inductors. That can easily be done with an ohmmeter, you should find a resistance of about 3 Ohm only between two of the pins, and these will be the correct ones.

In order to see if these differential pair oscillators work correctly, connect an oscilloscope through a 1:10 probe to the collectors of Q1, Q3 and Q6. You should see a 2.4Vpp sine wave on the oscilloscope with a frequency of about 290kHz at Q1 and Q3 and about 500kHz at Q6.

For all these tests, disconnect C2 and L4 from the collector of Q1, C6, C9 and Q5 from Q3 and L7, Q8, C16 and C12 from Q6/Q7 in order to get the "nude" oscillators working first.

C1, C3, C7 and C5 should be MICA capacitors for stability reasons.

Normally these oscillators work without problems, it's rather difficult to stop them. If you get no oscillation, there must be a design or layout problem. Are the feedback voltage dividers working?

Disconnect C3 form the collector of Q1 and inject a 290kHz sine wave with about 10Vpp into the free leg of C3. Connect the oscilloscope through a 1:1 probe to the base of Q2. Is there a 0.2Vpp sine wave? (similar for the other oscillators)

Let us know all this and we'll better be able to help you.

Thanks to Thierry and Chobs, i'm very grateful for your help.

I'll try first to check the pinout of the variable inductors, i think (...and hope) the problem could be there, if not i'll try to dismantle the circuits to desoldering the components for the test.
but...
i've not got a real oscilloscope, i use a pc software workalike an oscilloscope, it's name is Visual analyzer, i don't know if i can do the test you suggest me.

I've another question: on the "hotrodding mods" there's a tip for use an external volume pedal in place of volume antenna: if i well understand i must connect "VCA out" with 12v ...but if i do this i've not anymore 12v from the 7812...the voltage decrease to less than 1v...

A pc software will not help, since it works most probably through the sound input and is thus limited to 20kHz.

Most people don't understand that building a theremin is more complex than building a radio receiver and that one needs appropriate tools in order to do so.

If the supply voltage goes down when you connect VCA out to +12V, there is a big problem in your circuit!!! The VCA out is connected to PIN 12 of U3B, which is a simple current source and should not draw any current from an external input voltage. Out of that there are D5 which will get a reverse voltage and thus not conduct. R30 should have a value of 47k which will pull a current of about 0.5mA into pin 1 of U3A. All this cannot overload the 12V supply.

Why didn't you build and check the whole circuit systematically block by block instead of soldering all together and wondering why it doesn't work? That is not a professional approach.

The idea would be building first the three "nude" oscillators and only when they were working adding the two reactance stages around Q5 and Q8, then the antenna circuits and verifying each step with an oscilloscope and a frequency counter. Only after that one would build the resonance current detector around U3B and the mixer stage and last the waveshaping circuit/VCA around U3A. This would allow to make sure that every block works independently from the others and make a diagnose of problems much more easier.

If you were my student I would tell you to restart from the beginning... ;-)

Ok, i think 'ill do it from the beginning and redraw the layout ...this time all-in-one.