Elektor Formant Modular

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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