Cgs synth

Doh! I just had to re-install that pesky resistor to get the filter
clocking, but the minimum pitch of the oscillator is still very high,
even after turning the zero trimmer all the way down.

--- In cgs_synth@yahoogroups.com, "andrewlistmayer"
<andrewlistmayer@...> wrote:

>
> Ahh, thanks. Now it's oscillating alright, but really high pitched and
> not affecting the filter section. I guess this means I have a
> 4024-based problem. I'll look into it and collect some more data in
> case I still need help.
>
> --- In cgs_synth@yahoogroups.com, Scott Deyo <contact@> wrote:
> >
> > Dang! I forgot about a little boo-boo on the PCB. Link +15V to pin

1 of

> > the LM311 and you should be good to go.
> > It's not connected to anything right now... sorry!
> >
> > Cheers,
> > Scott Deyo
> > The Bridechamber
> > contact@
> > http://www.bridechamber.com
> > Jealous Edison Record Kompany
> > http://www.jealousedison.com
> >
> >
> > On Oct 15, 2008, at 2:21 AM, andrewlistmayer wrote:
> >
> > > I just read through this old thread because I have a similar problem
> > > with my Bi-n-Tic. I can get a filter sweep out of the last 20%

or so

> > > of the bandwidth knob, but the tuning knobs do nothing. This

leads me

> > > to believe that the center frequency is stuck somewhere below the
> > > audio range. So, I check the oscillator section. I also have a

slight

> > > amount of DC on pin6 of CA3140, so it isn't oscillating. I also

have

> > > voltage on pin 2, which is supposed to be at 0. Then, I start

at the

> > > beginning and try to figure out what is wrong. I can find no
> faults in
> > > the CV summing section, yet I only get between -.8 and barely
> above 0v
> > > depending on the coarse tune pot. Is this correct? Also, I am not
> > > getting +15 on pin 1 of the LM311 like it shows on the

schematic. The

> > > datasheet tells me this is a ground pin, so I'm not sure how
> important
> > > this is. I'm using a PN4391 fet and I matched the G, S and D on the
> > > PCB with the pinout on the fairchild datasheet. One last thing to
> note
> > > is that I'm using the bridechamber PCB. I didn't know what to do
> about
> > > the 100k resistor marked with a star, so I installed, then

removed it

> > > afterwards.
> > >
> > > I'm stumped at this point, so any hints would be greatly

appreciated.

> > >
> > > --- In cgs_synth@yahoogroups.com, sasami@ wrote:
> > > >
> > > > 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/>
> > > >
> > >
> > >
> > >
> >
> > [Non-text portions of this message have been removed]
> >
>