Cgs synth

Check your capacitor too. Make sure it is the right size. Make sure it is
actually soldered in - no bad joints, or not between the wrong holes. there
is a spare hole there to allow for different sizes. If you have the cap
between two the holes that are joined by the trackwork, it isn't going to work.

Also note that the pin-outs of different FETs varies. If I use the 2n4091, I
need to install it "backwards" to the marking on the PCB.

Ken

>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/>
>> Australian Miniature Horses & Ponies
><http://www.blaze.net.au/~sasami/>
>>
>
>
>
>
>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/>