Cgs synth

So, if the voltage on pin 2 & 3 is 0V and the 3140 gets it's
powersupply, it should create some AC voltage on pin 6 ?
I have only a DC voltage that varies between 0 & 0.86 VDC (depending
on the position of the coarse frequency pot )

thanks again for your help !
steven

--- In cgs_synth@yahoogroups.com, sasami@... wrote:
>
> You should never see any voltage on pin 2 of the 3140 - it is a
summing
> node. It is a basic op-amp feedback loop. Yhe opamp devotes its
entire time
> truing to keep pins 2 and 3 at exactly the same voltage. As pin 3
is 0v, pin
> 2 will be 0v. The current through the point will of course vary as
the
> output of the op-amp fights the current drawn through the LM394
(through the
> integrating capacitor and through the FET during reset).
>
> Ken
>
> >hello,
> >no luck so far, I've replaced the 2N4391 fet, but still no
voltage
> >on pin 2 of the ca3140. I've also measured with a scope to see
what
> >is exactly the output on pin 6 of the ca3140, and it shows only a
dc
> >voltage ( 0.86 V )
> >
> >any more clues ?
> >many thanks in advance !
> >steven
> >
> >--- In cgs_synth@yahoogroups.com, "stiebz" <theevaporizer@> wrote:
> >>
> >> hey,
> >>
> >> I used a 2n4391, I have no clue how I can check if it still is
> >> working properly, so I'll try to replace this compontent to see
if
> >it
> >> makes a difference.
> >>
> >> thanks,
> >> steven
> >>
> >> --- In cgs_synth@yahoogroups.com, "bbluthang" <jumpswine@>
wrote:
> >> >
> >> > Hi
> >> > look at the FET, what kind are you using? right way around etc
> >> > some FETS wont work in these ccts.
> >> > Andrew
> >> >
> >> >
> >> > --- In cgs_synth@yahoogroups.com, "stiebz" <theevaporizer@>
> >wrote:
> >> > >
> >> > > unfortunately my bintic filter is still not working...
> >> > > I've replaced the tl072, ca3140 and the lm394, but still
the
> >> > > oscillator part is not working as expected.
> >> > > I've noticed that depending on the setting of the frequency
> >> coarse
> >> > > pot, I have different readings on the circuit.
> >> > > I've added here a link to a part of the circuit diagram
where
> >> I've
> >> > > indicated some measurements done in both minimum and
maximum
> >> > > position of the frequency coarse potmeter. I hope somebody
can
> >> give
> >> > > me clue where more or less the problem should be with this
> >data.
> >> > > Thanks a lot in advance, you can find the drawing here :
> >> > > http://users.telenet.be/theevaporizer/modular/bintic.GIF
> >> > >
> >> > > steven
> >> > >
> >> > >
> >> > > --- In cgs_synth@yahoogroups.com, Romeo Fahl <rfahl@> wrote:
> >> > > >
> >> > > > one thing to keep in mind is that CA3140s are super
delicate
> >> ICs.
> >> > > > They are very sensitive to static, but it wouldn't
surprise
> >me
> >> if
> >> > > > hooking up power in reverse was too much for it to handle.
> >> > > >
> >> > > > Romeo
> >> > > >
> >> > > >
> >> > > > On Nov 4, 2006, at 6:08 AM, stiebz wrote:
> >> > > >
> >> > > > > No chips are hot ( and nothing smells burned )
> >> > > > > The TL072 seems to working fine, output 7 follows the
> >> frequency
> >> > > > > settings, but on the CA3140 I always measure 0.56 V on
pin
> >2
> >> and
> >> > > 1.1
> >> > > > > V on pin 6 regardless of the frequency setting. Would
this
> >> > > indicate
> >> > > > > a faillure on the CA3140 or the LM394 ?
> >> > > > > thanks !
> >> > > > > steven
> >> > > > >
> >> > > > > --- In cgs_synth@yahoogroups.com, sasami@ wrote:
> >> > > > > >
> >> > > > > > Test #1 - feel if any chip is getting hot. If it is,
> >> replace
> >> > > it.
> >> > > > > >
> >> > > > > > Ken
> >> > > > > >
> >> > > > > > >when i wanted to test my bin-n-tic, i incidently
> >switched
> >> +
> >> > > and -
> >> > > > > > >power supply. after i fixed the problem, I have no
sound
> >> > > > > whatsoever.
> >> > > > > > >I measured 1.1 volt between pin6 of the ca3140.
> >> > > > > > >Is there any part(s) that is the most likely to be
> >> damaged ?
> >> > > > > > >thx,
> >> > > > > > >steven
> >> > > > > > >
> >> > > > > > >--- In cgs_synth@yahoogroups.com, "kopernig"
> ><6079smith@>
> >> > > wrote:
> >> > > > > > >>
> >> > > > > > >> yes, i noticed the diode and put in a jumper...
but
> >> still no
> >> > > > > joy. i
> >> > > > > > >> don't have a scope (yet) but the voltage on pin
six
> >of
> >> the
> >> > > > > ca3140
> >> > > > > > >is
> >> > > > > > >> just under 1 volt. with an audio probe i can
(barely)
> >> hear
> >> > > a cv
> >> > > > > > >click.
> >> > > > > > >> so the vco is not oscillating. i can't figure out
why
> >> the
> >> > > 2n2
> >> > > > > > >> capacitor seems to be shorted... there's no
> >resistance
> >> > > between
> >> > > > > the
> >> > > > > > >> source and drain of the fet. nothing is physically
> >> shorted.
> >> > > a
> >> > > > > dead
> >> > > > > > >> fet? any ideas?
> >> > > > > > >> andrew.
> >> > > > > > >>
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >The CGS Modular Synth home page:
> >http://www.cgs.synth.net/
> >> > > > > > >
> >> > > > > > >Yahoo! Groups Links
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
__________________________________________________________
> >> > > > > __
> >> > > > > > Ken Stone sasami@
> >> > > > > > Modular Synth PCBs for sale
> >> > > > > <http://www.blaze.net.au/~sasami/synth/>
> >> > > > > > Australian Miniature Horses & Ponies
> >> > > > > <http://www.blaze.net.au/~sasami/>
> >> > > > > >
> >> > > > >
> >> > > > >
> >> > > > >
> >> > > >
> >> > > >
> >> > > >
> >> > > > [Non-text portions of this message have been removed]
> >> > > >
> >> > >
> >> >
> >>
> >
> >
> >
> >
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
>
_____________________________________________________________________
__
> Ken Stone sasami@...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
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<http://www.blaze.net.au/~sasami/>
>