Elektor Formant Modular

Unfortunately as I said this circuit is not straight forward. Do you have 
the original book. You can download the PDF there and if you can read 
english you will get a lot more information on the circuit.

Page 32 explains this section... (www.ftg.co.uk/studio/dl/elektorformant)

It pretty much covers that your output of IC1,  will be negative and for 
every 1V CV change then this should show -23.7mV of a change. As I said this 
is a scaling section. This should be scaled by adjusting P5.

So to me this section looks ok. But you could have an issue with the front 
panel potentiometers being connected wrongly. The book contains some errors 
so for this I used the schematic to confirm where each wire should go rather 
than the layout for the PCB.

Speak again soon.
Kris

>From: ganesha <goaqihai@...>
>Reply-To: ElektorFormant@yahoogroups.com
>To: ElektorFormant@yahoogroups.com, harrybissell@...
>Subject: Re: [ElektorFormant] problem with formant pro vco (new design)
>Date: Sun, 9 Apr 2006 21:12:07 +0100 (BST)
>
>Hi Harry,
>Thanks for you reply.
>IC 6 is a CA3086 transistor array.
>You can take a look at the schematic here:
>http://www.krinkel.be/formant/schematic.jpg
>I've written in red the points where I measure and the
>results I read on my DVM.
>I think the problem is my cv and rangevoltage become
>0V after the resitors so nothing is going into theIC1
>opamp, but I have no idea why this is happening.
>
>regards, Kris
>
>--- harrybissell <harrybissell@...> wrote:
>
>
>---------------------------------
>I'm not looking at the schematic... but I guess that
>IC6-p2 is the inverting input of an opamp with
>negative
>feedback and used as a summing or inverting amp.
>
>Voltages in this circuit are actually converted to
>currents in the resistors.  A positive current in the
>input
>is cancelled out by a negative current in the
>feedback...
>so the net voltage at IC6-p2 sould be whatever the
>non-inverting
>input (IC6-p3 ?) is. If that is zero volts, so should
>pin 2 be.
>
>an educated guess...
>
>H^) harry
>
>ganesha wrote:
> >
> > Hello Kris
> > I just did some measurements and have no voltage at
> > pin2 of ic6. I'm pretty sure, the problem is caused
>by
> > the resistors R5, R6  and R3.
> > For example: I feed A 3V cv source. If I measure it
> > right before R3 it is 3v, but right after R3 it is
>0V
> > so it looks to me the R3 is blocking the whole
>thing.
> > The same with R6 For the range. I turn the
> > rangepotmeter open so I put 12V in. But right after
>R6
> > I measure 0V.
> > Can you please measure what voltage you have right
> > after R3 if you feed it a cv of 3V? (When you have
>the
> > time ofcourse)
> >
> > regards, Kris
> >
> > --- Kris Bishop <bishopkris40@...> wrote:
> >
> > ---------------------------------
> > I live in Scotland and have the strangest name,
> > everyone asks where it is
> > from. Can you imagine how strange this is lol
> >
> > Kris, First how good is your english
> > second how good is your understanding of the
> > electronics in this synth?
> >
> > I'm not that good and I managed this so here we go:
> >
> > First,
> >
> > Do not under any circumstances change any components
> > unless you have read on
> > the internet to do so. This is important as the VCO
>is
> > based on a lot of
> > electronic and electrical values that are dependant
>on
> > each other.
> >
> > you were correct about r1 I have marked this as
>wrong
> > in the book (cannot
> > remember why??) but I am sure if you put the
>original
> > value back in then we
> > can work from here. (Next week I will open my synth
> > and check my value, but
> > moving house so please be patient)
> >
> > What you want with nothing other than a CV is for
>the
> > current out of IC6 pin
> > 5 to double for every 1v change. This is the key to
> > controlliing the synth.
> >
> > This said we can remove this device and insert a
> > current, First you need to
> > check what you are getting at pin 2 of IC 6. this is
>a
> > voltage so is easy to
> > test. make sure that you are getting something here,
> > 1v, 5v whatever. now if
> > you can monitor the current from pin 5 of IC 6. what
> > do you get and if you
> > increase CV by 1V what do you get. (This section is
> > only used to scale the
> > input CV)
> >
> > ok so you get the correct operation from IC6
>(CA3086)
> > You must be using
> > this. there is other methods but no for this
>circuit.
> >
> > no matter what happens if you get a current in to P7
> > or input to IC2 then
> > you should see Oscillations. I hope at this point
>like
> > me everything is ok
> > until now as this is where I had a problem. IC5 is a
> > comparitor of sorts. we
> > need the voltages to be different to get this
>circuit
> > to work.
> >
> > Sorry but I'll come back to help in the next few
>days.
> > But please did you
> > get any sound at the start. also are you trying to
> > build 1 or 2 VCO's??
> > Where did you get your CA3086's from? I had 5 of
>these
> > and only 3
> > worked.....
> >
> > I did not carry out any tests from the book as I do
> > not speak German but I
> > did get good results after checking all components
>and
> > soldering. Your
> > circuit looks good but what does the other side look
> > like? Mine is messy but
> > works so don't worry. Where do you get your CV from.
> > Sorry I need more info
> > for the next step.
> >
> > If you want when I am at work I can talk to you on
> > Skype if you'd prefer but
> > I hope you speak english. We can even just use the
> > chat by text option if
> > you want but we can arrange a time. Probably
>Thursday
> > or Friday night is
> > best, I work night shifts then.
> >
> > Bishop (Kris)
> >
> > >From: ganesha <goaqihai@...>
> > >Reply-To: ElektorFormant@yahoogroups.com
> > >To: ElektorFormant@yahoogroups.com
> > >CC: bishopkris40@...
> > >Subject: RE: [ElektorFormant] problem with formant
> > pro vco (new design)
> > >Date: Sat, 8 Apr 2006 09:43:02 +0100 (BST)
> > >
> > >Hi Kris, ;-) feels like I'm writing something to
> > >myself.
> > >
> > >
> > >Thanks for your reply. I'll try to descibe the
> > >different steps I did.
> > >
> > >In the beginning everything went fine, I've build
>the
> > >eingangsspannungaddierers, exponentiators and
> > heizung.
> > >I plugged it in and after 20 minutes I have set the
> > >voltage at kollektor tr 4 to 1.6V with trimmer
> > >p8. So far no problem,I then continued building the
> > >Sawtoothoscillator without soldering Tr3 so I could
> > >meassure the current between kollektor tr3 and pin3
> > of
> > >ic2. I also made the abgleichskeyboard (I had to
> > >replace R1 with 47K because otherwise my maximum
>for
> > >switch 5 was 2.86 V instead of 4 V) and soldered
>the
> > >pots for range and tune to the VCO pcb. I then
>tried
> > >to messure the current that is supposed to be
>0.002mA
> > >but
> > >nomather what switch I used on the
>abgleichskeyboard,
> > >or to what position I turned the range and
>fine-tune
> > >pots, I'm allways measuring 0,000mA. I thought
> > >maybe I did not solder enough components on the pcb
> > >because of the difference between the book and the
> > new
> > >design so I continued the entire pcb except for
>tr3.
> > >But still no result. At the end as a last resort, I
> > >also soldered tr3 in position but still no current.
> > >Can you tell me what measurement I can do to track
> > the
> > >fault? On strange thing I allready noticed is that
>if
> > >I meassure betweent the mass and before R5 (range)
>I
> > >have 11.84V because I set the range pot fully open.
> > >But after R5 (100K) I measure 0V. I suppose this is
> > >not normal and that is the cause why turning the
> > range
> > >pot has no influence? So is the 100K to big?
> > >Also would it be a problem that after the 7812
>(ic7)
> > >there is only 11.84V instead of 12V?
> > >
> > >I've uploaded a pic of the vco to
> > >http://www.krinkel.be/formant/formantVCO.JPG
> > >
> > >best regards,
> > >Kris
> > >
> > >
> > >
> > >---------------------------------
> > >I'll reply here and on personal, as the group is
>here
> > >so that people like us
> > >can search problems first then ask.
> > >
> > >I'll help, but moving house so I can only promise
>you
> > >an answer by Tuesday,
> > >when I go back to work. What is the problem mate?
> > >
> > >Regards
> > >Kris
> > >
> > >
> > > >From: ganesha <goaqihai@...>
> > > >Reply-To: ElektorFormant@yahoogroups.com
> > > >To: ElektorFormant@yahoogroups.com
> > > >CC: synth-diy@...
> > > >Subject: [ElektorFormant] problem with formant
>pro
> > >vco (new design)
> > > >Date: Fri, 7 Apr 2006 23:25:54 +0100 (BST)
> > > >
> > > >Hi,
> > > >
> > > >I'm building the formant pro vco from the book of
> > > >Hans-Joachim Helmstedt. But I'm having a problem
> > that
> > > >I cannot solve myself. Is there anyone who has
> > >already
> > > >built it and who would like to assist me?
> > > >Please contact me off-list so I can send you a
>mail
> > > >where I describe the problem.
> > > >
> > > >Thanks in advance!
> > > >regards, Kris
> > > >
> > > >
> > > >
> > >
> >
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