[sdiy] Old unique VCO - T?==?windows-1256?Q?une drifting problem - adapting a servo c?==?windows-1256?Q?onversionþ

Matthias Herrmann-DEU Matthias.Herrmann at jeppesen.com
Mon May 14 14:00:44 CEST 2012


and tom gamble's EFM VCO 3D:
http://www.modular.fonik.de/files/EFMforum/orgEFMfiles/vco3d.pdf

cheers,
matthias


> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of ChristianH
> Sent: Monday, May 14, 2012 1:38 PM
> 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?onversionþ
> 
> On Fri, 11 May 2012 14:49:21 +0000 Gergo Palatinszky
> <Gergo_Palatinszky at epam.com> wrote:
> 
> > 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 Doepfer MS-404 did it too: http://www.doepfer.de/ms404_sm.htm
> (O2 below the expo pair/glide is the heater regulator)
> 
> Chris
> 
> 
> 
> > -----Original Message-----
> > From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of rtarcan
> > Sent: Friday, May 11, 2012 4:42 PM
> > 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?onversionþ
> >
> > The tempco resistor only compansates VT parameter of transistor but
> not IEBS of transistors( Emetor -Bas saturation current of transistors)
> witch drifts too much with ambient temperature. But heating the
> transistors as used in uA726 compansates both...
> > On 11.05.2012 16:03, Idris El Kasri wrote:
> > >    Hi everybody!
> > >
> > > I got an old modular synth from the 70's that was previously owned
> by Brendon Pollard, and previously (the legend says) by Jethro Tull,
> here's a pic :
> > > http://www.muffwiggler.com/forum/files/elvis_big_351.jpg
> > >
> > >    The VCOs are totally incredible, I'd say comparable to Jurgen
> Haible's Living VCOs and maybe even fatter (without any kind of
> disrespect of the giant J.Haible's memory).. Some UA726 unfortunately
> passed away, Y.Usson kindely advised me to replace them by a tempco and
> a lm394/or ssm2210 (mat02 etc...)...
> > >
> > >    The problem is that the tune drifts a lot!
> > > For example, I tune it on a C2, 20s later it becomes à B2 then a
> A#2 etc etc during maybe 1h or more then it would becomes higher and
> higher... big problem!
> > >
> > >    Yves advised me to check conversion's capacitor (to put a low t°
> drift capacitor) and power supply's stability, which I did and the
> problem remains; he said that considering that there was no servo
> conversion on this old VCOs from the beginning of the 70s (having a
> look at the dates on the AOPs) I shoudn't hope very good stability...
> > >
> > >    Here is the schematic of the VCO :
> > > http://img826.imageshack.us/img826/646/vco2shematic.jpg
> > >
> > >     I didn't found much documentation on the "servo conversion"...
> > >
> > > Somebody could advise me some things to try to adapt a servo
> conversion on this VCOs? I m really lost...
> > >
> > > I'm sure that if we can fix that pbm we could really have here some
> really wild VCOs...
> > >
> > >
> > >
> > >    Cheers.
> 
> 
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