[sdiy] Anybody worked with real Moog System 55 ?

[Jean-Pierre Desrochers]

I should have specified that in my 'Moog system 55 clone' project
only the front panels and dotcom frame sizes will have the same look
as the original Moog. The circuits will be made with more stable
components and available parts. 
I don't care about the old 921A, B VCO's technology
and won't rebuild using the same circuits..
Sorry about the confusion I brought here.

I only care about the Allen Bradley pots used at that time.
like this one:
http://www.amparchives.com/Amp%20Archives/Marshall/Data%20Sheets/PEC%20K%20Series%20Potentiometers.pdf

So my question was:  
Would these pots be that bad to control a 'stable' VCO circuit ?
JP

--------------------------------------------------------------------


 On Mon 27/09/10 23:57 , gino wong wonggster at gmail.com sent:
>  The 55s oscillators stayed in tune after warming up and are way more
> stable than earlier ones, however they still will be needed to be tuned up
> during use as needed  some days a lot, some days not at all, The pots
> aren't really an issue  set em they stay.  The Moog idea was to replace
> them with ones that work when they break, they actually not that picky if
> you could adjust it to spec any parts were fine . 
> gw
> 
> On Mon, Sep 27, 2010 at 9:36 AM, Jean-Pierre Desrochers  wrote:
> 
> Does anybody worked with real Moog System 55 ?
> 
> I'm building a VCO driver which will be very close
> to the Moog system 55's  921A VCO driver design (parts & front panel).
> I'm wondering about the stability of Allen Bradley pots used in such a
> design in late 60's.
> I'm considering instead Vishay 249 series pots for FREQUENCY front
> adjustment
> but they only are capable of 295deg mechanical rotation compared
> to the original Allen Bradley's 320deg mechanical...
> This would have an effect on the front panel FREQ divisions
> (smaller span).
> Since Allen Bradley doesn't exist anymore I'd use PEC pots
> like this:
> 
> http://media.digikey.com/pdf/Data%20Sheets/Precision%20Electronic%20Compone
> nts%20Ltd%20PDFs/MIL%20Style%20RV4.pdf?cshift_ck=1830796695cs506374199&clie
> nt_id=5042[1]
> 
> So my question is:
> Were the original Allen Bradly pots that bad
> about freq stability (carbon type) or this would still be
> a 'fair' choice to me today ?
> JP
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> Links:
> ------
> [1]
> http://media.digikey.com/pdf/Data%20Sheets/Precision%20Electronic%20Compone
> nts%20Ltd%20PDFs/MIL%20Style%20RV4.pdf?cshift_ck=1830796695cs506374199&clie
> nt_id=5042[2] http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 
>