[sdiy] Again- LFO, working

[xmurz at gmx.de]

> No reason for it not to work with two packages. Might have some
> probalem with how you disabled the unused sections... or what
> ELSE those sections were used for. If you try it again... I usually
> ground the unused non-inverting input... and tie the usused output to
> the unused inverting input...

I had the unused section disconnected. (so I guess it was "floating")
When I touched the input-pins of the opamp, it would pick up
the static of my hand and amplify it. When I disconnected the
-12 V power, and held this pin with my hand, it would start to
oscillate. (but with a distorted wavform) 
I think this was due to the "floating" pins of the unused section.
Hmmm, and those 2 sections are not really seperate units,
as they share "parts".. transistors. (I should have thought about this
fact beforehand)


> 
> making a voltage follower with ground for an input. This is usually
> a good way to tie unused opamps... with a few exceptions (that someone
> else will fill in...)

Good advice!

Regards,
  Hans

> 
> H^) harry
> 
> 
> >From: xmurz at gmx.de
> >To: synth-diy at dropmix.xs4all.nl
> >Subject: [sdiy] Again- LFO, working
> >Date: Fri, 29 Mar 2002 13:22:01 +0100 (MET)
> >
> >Hello!
> >
> >The 2 LFO's I tried (ASM-1 and Modulus) were not working.
> >
> >The Modulus e-zines can be found at:
> >http://www.modulus.wavesynth.com/modular/modular.htm
> >(as somebody asked for the address)
> >
> >I now got the ASM-1 LFO to work nicely.
> >The problem was, that I had the non inverting opamp
> >on one TL082, and the inverting opamp on another TL082.
> >Now that I got both parts on one TL082 it works.
> >(Don't ask my, why I dit it with 2, to begin with.)
> >
> >Now my question:
> >Why is it not working with 2 seperate opamps???
> >
> >Then there is the 22R Resitor. I substituted a
> >trimmer for that part, because a 22R value caused
> >my LFO to go towards (aproximately) 10V + without
> >returning back down on the lowest LFO speed.
> >
> >A trimmer enables me to get to poti down to very
> >low speed without going up to 10V+.
> >The trimmer will set be set to >22R
> >
> >Is that normal???
> >
> >Will all parts of the ASM-1 work on a +-12V PSU?
> >
> >Regards,
> >   Hans

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