YES That works perfectly.
these analog circuits sure are tempermental. Why do different people
get completely different results? Ive had a few modules now where
I've had to change out components. 1/2 the people who helped me say
"it should work fine as it is in the schematics" and the other 1/2 say
"I had to change such and such to get it to work"
Owell..
Thanks for your help!!
these analog circuits sure are tempermental. Why do different people
get completely different results? Ive had a few modules now where
I've had to change out components. 1/2 the people who helped me say
"it should work fine as it is in the schematics" and the other 1/2 say
"I had to change such and such to get it to work"
Owell..
Thanks for your help!!
--- In cgs_synth@yahoogroups.com, "josh summitt" <ascetik@...> wrote:
>
> I've built two of these VCO's and on both of them i had to lower the
gain so
> that the SAW would not hit the voltage rails. I changed the 330k
resistor in
> the feedback loop of the tl072. Change it to a lower value. It
should not
> take much like maybe a 250k or something. I can't remember exactly
what i
> used.
> Josh
>
> On 3/8/06, c10h14no2i <c10h14no2i@...> wrote:
> >
> > I did check both resistors.. I even replaced them with what you have
> > specified in the schemo's.
> >
> > When I test using the AC output from the VCO, I get +5/-15 volts.
> > When I test w/ the DC output from the VCO the bottom of the wave
> > starts at about +10 volts, and goes up to where I guess its clipping.
> > I dont understand why there is such a difference between the ac and dc
> > outputs. (does that give you any clues?)
> >
> > Then I dont understand why the square output is centered on 0, when it
> > is getting its input from the saw, which is messed up.
> >
> > Also, I tested the output of the ca3140, and its a perfect saw
> > centered on 0
> >
> > That sure narrows down where the trouble could be coming form.
> > BUT, I have gone through, checked every component around the tl072,
> > and heated each solder point to make sure its good. Still have the
> > same problem. I know the circuit works, so Ive got to be missing
> > something... I just can't find it!
> > Is it possible that something is wrong w/ the tl074? Can an IC kind
> > of work, or are they just good or bad? (unfortunately I built this
> > module before I learned the value of ic sockets)
> >
> > Thanks again.
> >
> >
> > --- In cgs_synth@yahoogroups.com, sasami@ wrote:
> > >
> > > The 240k is the offset resistor. it sounds like the resistor you
have in
> > > there is too small, perhaps not a 270k at all.
> > >
> > > Ken
> > >
> > > >Sorry for the basic question, but which are the offset
resistors? The
> > > >ones around the tl072 that outputs to the saw out?
> > > >
> > > >If so, I should mention I am using a 270k instead of the 240k,
and a
> > > >560k instead of the 330k, which is what the elby instructions
said to
> > > >do. I think everything else is per the schematics.
> > > >
> > > >
> > > >--- In cgs_synth@yahoogroups.com, sasami@ wrote:
> > > >>
> > > >> Usually caused by the signal hitting a power rail and running
out of
> > > >> anywhere to go. It's what i'd expect to find if an offset
resistor
> > > >was not
> > > >> soldered in propperly (or the wrong value), or some other voltage
> > > >> determining part. The name givven to this is "clipping".
> > > >>
> > > >> Ken
> > > >>
> > > >> >I got a working scope today, and the saw out of the VCO is very
> > > >> >strange. Rather than /|/|/|/| it goes -\-\-\-\. That is the
> > best I
> > > >> >can do, but the 1st example should be a normal saw, and the 2nd
> > > >> >example, whats going on is that it goes straight up, has a flat
> > top,
> > > >> >then slopes down. I tested my paia VCO and the shapes are fine,
> > so Im
> > > >> >sure Im using the scope correctly.
> > > >> >Any idea what could be causing this?
> > > >> >
> > > >> >Thanks,
> > > >> >Scott
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> > > >> >
> > > >> >Yahoo! Groups Links
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >> >
> > > >>
> >
_______________________________________________________________________
> > > >> Ken Stone sasami@ or sasami@
> > > >> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/<http://www.blaze.net.au/%7Esasami/synth/>
> > >
> > > >> Australian Miniature Horses & Ponies
> > <http://www.blaze.net.au/~sasami/
<http://www.blaze.net.au/%7Esasami/>>
> > > >>
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >The CGS Modular Synth home page: http://www.cgs.synth.net/
> > > >
> > > >Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
_______________________________________________________________________
> > > Ken Stone sasami@ or sasami@
> > > Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/<http://www.blaze.net.au/%7Esasami/synth/>
> > >
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> >
> >
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> >
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