# [sdiy] Old unique VCO - Tune drifting problem - adapting a servo conversion‏

Idris El Kasri idris1er at hotmail.com
Wed Jun 13 17:41:06 CEST 2012

```  Sorry, if I disconnect the collector of the conversion transistor on the original circuit (http://img826.imageshack.us/img826/646/vco2shematic.jpg) I got for instance -9,7V on the collector and -9,2V on the base...
Is it possible to get these values with a matched pair for the conversion?
I found this doc for the exponential conversion with a matched pair but unfortunately I m not really into these mathematical formulas... mathematical formula
http://electronotes.netfirms.com/s019.pdf

----------------------------------------
> From: idris1er at hotmail.com
> To: synth-diy at dropmix.xs4all.nl
> Date: Wed, 13 Jun 2012 05:27:06 +0200
> Subject: Re: [sdiy] Old unique VCO - Tune drifting problem - adapting a servo conversion‏
>
>
>
> It seems that I need something like -1V/-2V on the collector of the right-hand transistor at less to begin to create a waveform, I tried a lot of things but I can't get more than ~ -680mV ....
>
> > From: idris1er at hotmail.com
> > To: alan.needham at centrica.com; gergo_palatinszky at epam.com; synth-diy at dropmix.xs4all.nl
> > Date: Tue, 12 Jun 2012 06:15:16 +0200
> > Subject: Re: [sdiy] Old unique VCO - Tune drifting problem - adapting a servo conversion‏
> >
> >
> >   hi everybody!
> > I've tried the thermoregulating circuit from the Minisonic ! thanx Alan ;)
> >    It reduces pretty well the drifting pbm, with a good bias setting at the best I can get maybe  one 1/4tone up or down within 1h30~2h
> >
> >   So not bad result but not the solid as a rock stability, is it the servo convertion with a matched pair that could bring that?
> > I don't know how to adapt that kind of conversion on the circuit, here's the schematic :
> > http://img826.imageshack.us/img826/646/vco2shematic.jpg
> >
> > I've tried that without any result... :(
> > http://img337.imageshack.us/img337/1861/servow.jpg
> >
> >   I beg for your help S-Diy-list...  :)
> >
> >
> >
> >
> > > Date: Fri, 11 May 2012 17:56:10 +0100
> > > From: Alan.Needham at centrica.com
> > > To: Gergo_Palatinszky at epam.com; synth-diy at dropmix.xs4all.nl
> > > Subject: Re: [sdiy] Old unique VCO - T?==?windows-1256?Q?une drifting problem - adapting a servo c?==?windows-1256?Q?onversion‏
> > >
> > > The PE Minisonic had an oven as an option.
> > > http://www.timstinchcombe.co.uk/synth/pe_mini/pe_mini_feb_75.pdf
> > > Circuit on magazine page 145 (pdf page 6 of 7)
> > > I remember it taking about a minute to settle.
> > >
> > >
> > > -----Original Message-----
> > > From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Gergo Palatinszky
> > > Sent: 11 May 2012 15:49
> > > To: synth-diy at dropmix.xs4all.nl
> > > Subject: Re: [sdiy] Old unique VCO - T?==?windows-1256?Q?une drifting problem - adapting a servo c?==?windows-1256?Q?onversion‏
> > >
> > > Hi,
> > >
> > > What about using a 3046(3086) and use one of the spare transistor inside as heater ... ASM-2 did this way if I'm right ....
> > >
> > > Br,
> > > Pala
> > >
> > >
> > >
> > > _____________________________________________________________________
> > > The information contained in or attached to this email is intended only for the use of the individual or entity to which it is addressed. If you are not the intended recipient, or a person responsible for delivering it to the intended recipient, you are not authorised to and must not disclose, copy,distribute, or retain this message or any part of it. It may contain information which is confidential and/or covered by legal professional or other privilege (or other rules or laws with similar effect in jurisdictions outside England and Wales).
> > >
> > > The views expressed in this email are not necessarily the views of Centrica plc, and the company, its directors, officers or employees make no representation or accept any liability for its accuracy or completeness unless expressly stated to the contrary.
> > >
> > > British Gas Services Limited and Centrica Energy (Trading) Limited, both wholly owned subsidiaries of Centrica PLC, are authorised and regulated by the Financial Services Authority.
> > >
> > > Registered office: Millstream, Maidenhead Road, Windsor, Berkshire SL4 5GD
> > >
> > > Registered in England No 3141243.
> > >
> > > Centrica plc
> > >
> > > Registered office: Millstream, Maidenhead Road, Windsor, Berkshire SL4 5GD
> > >
> > > Registered in England and Wales No 3033654
> > > _______________________________________________
> > > Synth-diy mailing list
> > > Synth-diy at dropmix.xs4all.nl
> > > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> >
> > _______________________________________________
> > Synth-diy mailing list
> > Synth-diy at dropmix.xs4all.nl
> > http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy

```