Cgs synth

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/>