[sdiy] uA726, heated pairs...

[James Patchell]

         Yes, and no...depends on how you are going to use the VCO's...if 
all three VCO's are going to be controlled by the same pitch source all of 
the time...sure...but for a true modular system, this would not work well.

         -Jim

At 11:21 AM 8/8/2003 -0700, Gene Stopp wrote:
>BTW the Voyager uses MAT-04 per VCO, which I would guess is the expo. I have
>not felt them during operation to see if they are oven-ized. Interestingly
>enough there is one tempco in there. Maybe one tempco for all three VCO's?
>Since it's the scale factor that's getting tempco'ed, and all 3 VCO's are
>tracking the CV source, does this not sound like an elegant way to reduce
>the tempco count?
>
>- Gene
>
>
>-----Original Message-----
>From: Tim Ressel [mailto:madhun2001 at yahoo.com]
>Sent: Friday, August 08, 2003 11:12 AM
>To: Grant Richter; synth-diy at dropmix.xs4all.nl
>Subject: Re: [sdiy] uA726, heated pairs...
>
>
>Grant,
>
>The substrate needs to be connected to the lowest
>voltage the IC will see. In my case I didn't see that
>part of the datasheet until after I had wired the
>circuit. So I made that transistor unused and replaced
>it with an external 2N4401. Pin 13 (substrate) is tied
>to -V. The 2N4401 replaces the transistor that serves
>as a clamp for the output transistor. I used the same
>scheme when I used a MAT04 which has only 4
>transistors.
>
>--tr
>
>
>--- Grant Richter <grichter at asapnet.net> wrote:
> > Do you remember what you did with the substrate pin?
> >
> > open, ground or -15V?
> >
> > > From: Tim Ressel <madhun2001 at yahoo.com>
> > > Date: Fri, 8 Aug 2003 09:23:59 -0700 (PDT)
> > > To: Grant Richter <grichter at asapnet.net>, Keith
> > Daniel <ensign7 at e-scape.net>,
> > > synth-diy at dropmix.xs4all.nl
> > > Subject: Re: [sdiy] uA726, heated pairs...
> > >
> > > Yo,
> > >
> > > I use the heater circuit from AN299 on my VCOs.
> > One
> > > uses a 3046, the other uses a MAT04. It works as
> > > advertised. I checked the circuit in an
> > environmental
> > > chamber so I could verify operation up to +40C.
> > >
> > > --tr
> > >
> > >
> > > --- Grant Richter <grichter at asapnet.net> wrote:
> > >>> There is the little known National Semiconductor
> > >> app note AN-299 (1986?),
> > >>> where an LM3046 transistor array is used to
> > >> provide a heated pair for a VCO.
> > >>>
> > >>> I've tried it, but it seems to me that there was
> > a
> > >> change in chip manufacture,
> > >>> and it doesn't work as advertised. The substrate
> > >> pin is the problem.
> > >>>
> > >>
> > >> Just a couple stray thoughts...
> > >>
> > >> The ap note doesn't specify the pin out on the
> > >> CA3046. You could probably
> > >> get it to work by trying different combinations
> > of
> > >> heater and sensor
> > >> transistor.
> > >>
> > >> Also, the substrate connects to the most negative
> > >> voltage used, in this
> > >> case, it looks like ground and not -15V.
> > >>
> > >> For a working example, see the Moog "Source"
> > service
> > >> manual which used a
> > >> thermostated CA3046 for the expo-converter. The
> > >> Serge NTO and PCO also use a
> > >> heated CA3046.
> > >>
> > >
> > >
> > > __________________________________
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>
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