Doepfer

Dieter,

A while ago I asked you about the mod mentioned at the bottom of this page, 
creating an insert to the A-155 GLIDE section for returning a 156-quantized, 
PRE-OUT signal.    You said that such an insert should be placed between Pin 
8/TL064 --- and ----  Pin 4/CD4053.   I asked Shawn ( US Rep )  to 
cross-check your instructions with the service manual since they did not 
seem to match my A-155 PCB.  I think the service manual and therefore your 
advice might have been "backwards".

   According to Shawn, the service manual shows, as you said, Pin 8/TL064 
connecting to Pin4/CD4053, and Pins 3 and 5 of CD4053 connecting to the S/H 
polarity jumper.   My PCB has this "switch" and jumper the other way 
around....so Pin 8/TL064 connects to center pin of jumper, outer pins of 
jumper still connect to Pins 3 and 5 of CD4053, and Pin 4/CD4053 connects to 
a cap and Pin 12/TL064.  Phew.

OK, so the mod should actually go between pin 8 of TL064 and the center pin 
of S/H jumper, correct?

While you have the schematics at hand........ I also asked about adding a 
set of AC coupling caps and a switch for when I want to use A-155 as graphic 
VCO.   I've been trying to decide where to place them so that I can effect 
both PRE and POST outs with one cap per CV row.  I could wire things around 
Pin 8/TL064 to make it work, but can I put the caps between Pin7/TL064 and 
R3 so that both outputs are AC coupled?

  I sincerely appreciate you time and your help.  Thank you.

Nicholas Keller

=============================

>From: "Dieter Doepfer" <hardware@doepfer.de>
>Reply-To: Doepfer_a100@yahoogroups.com
>To: <Doepfer_a100@yahoogroups.com>
>Subject: AW: [Doepfer_a100] A-155 mod question
>Date: Mon, 19 Sep 2005 12:53:37 +0200
>
>
>
> > -----Urspr�ngliche Nachricht-----
> > Von: Doepfer_a100@yahoogroups.com
> > [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von Nicholas Keller
> > Gesendet: Sonntag, 18. September 2005 21:00
> > An: Doepfer_a100@yahoogroups.com
> > Betreff: [Doepfer_a100] A-155 mod question
> >
> >
> > I would like to add a send/return loop to the voltage rows of my A-155
> > so I can run the signals to A-156 Quantizer before routing them back
> > through the slew limiters inside A-155.
> >
> > Any ideas?  Dieter?
> >
> > I know I could use the PRE-OUT as my send, so a single normalled
> > socket interrupting the signal going to the slew limiter would be all
> > I'd need to add......  but where exactly can I make this
> > interruption?  Shouldn't it be between the center pin of J2
> > (potentiometer board)....and where that trace branches off to C2 and
> > IC3,pin12 ?
>
>No. That's not the right point.
>
> > That seems correct to me, but all help is appreciated.
>
>No. You have to make the insert between pin 8 of the TL084 (output OpAmp 
>O3)
>and pin 4 of the electronic switch (CD4053) that is used for the S&H
>circuit. An of course an additional socket is required for the insert
>function.
>
>Best wishes
>Dieter Doepfer
>

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