Doepfer

Ingo,

thank you for the translation (and sorry for my late response but I was very
bus last week even because of the A-100 live event in the Munic culture
center "GASTEIG"). This is indeed the explanation.

The most important part is the z-diode (5V1 or 5V6) between the control
voltage inputs of the CEM3382/PA382 and GND. This limits the control voltage
appearing the CV inputs to about +5V. Turning the manual frequency knob
fully CW and adding an external voltage could exceed +5V and the CEM3382
will stop working.

From the records of Roland Mayer (he was responsible for the A-126 and it's
modification) all A-126 manufactured ~ summer 1999 and later should be
already equipped with the additional parts of your translation (especially
the z-diode). Only for older A-126 (production before summer 1999) the
modifications should be missing. It is very easy to find out if the module
has been modified: at the bottom of the pc board several parts should be
soldered in addition.

I have a MS word document available that shows the bottom of the pc board
and all additionally parts. Please contact me directly (hardware@doepfer.de)
and I will send the document to anybody who is interested.

Best wishes
Dieter Doepfer


Additional information: As of now only A-100 PSU II will be manufactured
(toroid/ring core transformer, 1200mA). The old version of the A-100 PSU
(standard transformer, 650mA) will be no longer manufactured. We sell the
old version only while stocks last.


> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com
> [mailto:Doepfer_a100@yahoogroups.com]Im Auftrag von selfoscillate
> Gesendet: Samstag, 12. November 2005 13:46
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-126 VCFS (Frequency Shifter) Problem
>
> hello,
>
> i checked the service manual of the a126 and i think
> that i found the possible reasons for the malfunction,
> but these should only occour with the first two
> production series of the a126. a freshly
> purchased a126 shouldn't have these problems
> and should be returned for service in that case.
>
> this is a rough translation from german to english,
> i apologize for possible errors. if somebody is
> interested, i can post the full text in german.
> i guess this is ok, dieter?
>
> 1. check the ic5 and ic9 on the pcb. if these are tl064,
> then maybe they should be replaced with tl084.
>
> 2. the sine/cosine vco is built around a cem3382,
> which works correctly in a range of 50 - 5000 hz.
> however, if you turn the freq knob fully cw and
> apply a control voltage, you may go beyond these
> limits and the cem3382 stops oscillating.
> this happens when the voltage applied to the cem3382 ic
> exceeds +6 volts. to prevent this, a 5.6 volts zener diode
> has to be inserted between ground and the voltage inputs
> of the cem3382 (the anode to ground).
>
> 3. when the a126 is modulated with a square wave at
> audio frequencies, then under rare circumstances the
> cem3382 stops oscillating too. this can be prevented
> by adding a 1nf capacitor between r51 and p12.
>
> hope this helps clearing up the issue.
>
> best wishes
>
> ingo
>
>
>
> --- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe"
> <timothy@t...> wrote:
> >
> > I'm not aware of any problem like this with mine, but from memory,
> > the amplitude of the internal oscillator takes a while to settle
> down
> > after a CV change, and so (I'm guessing here) maybe at high CV it
> is
> > possible that it might stop running completely. I'll check it out
> > later today and report back then...
> >
> > Tim
> >
> > > same problem with mine,
> > > anyone got a solution to it..?
> > >
> > > /daniel
> > >
> > >
> > >
> > >
> > > --- In Doepfer_a100@yahoogroups.com, "Tommy DOG" <mrsvomit@t...>
> > wrote:
> > > >
> > > > Then mine does too.
> > > > It's always behaved like that.
> > > >
> > > > TD
> > > >
> > > > --- In Doepfer_a100@yahoogroups.com, Bakis Sirros
> > <synth_freak_2000@y...>
> > > wrote:
> > > > >
> > > > > hello zoran,
> > > > > it seems to me that your a126 vcfs needs repair.
> > > > > bakis.
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > --- Zoran Bosnjak <dj_allin@h...> wrote:
> > > > >
> > > > > >
> > > > > > Hello,
> > > > > >
> > > > > > I purchased A-126 VCFS (Frequency Shifter) recently,
> > > > > > and I noticed that when
> > > > > > rotating Shift knob towards value 10, and applying
> > > > > > control voltage to CV1,
> > > > > > the module stops functioning. I have to turn the
> > > > > > whole case off and on, to
> > > > > > reset it and have it work again.
> > > > > >
> > > > > > Is this behaviour by design or my unit is faulty ?
> > > > > >
> > > > > > Regards,
> > > > > >
> > > > > > Zoran
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > > Bakis Sirros
> > > > > Parallel Worlds
> > > > > Athens-Greece
> > > > > [Doepfer_a100] group owner
> > > > > http://www.shimarecords.co.uk
> > > > > http://www.rubber.gr
> > > > >
> > > > >
> > > > >
> > > > > __________________________________
> > > > > Yahoo! FareChase: Search multiple travel sites in one click.
> > > > > http://farechase.yahoo.com
> > > > >
> > > >
> > >
> >
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