Doepfer

Well done Ingo! After spending some minutes with mine and taking some 
readings etc., it was clear it works fine, and then I discovered my 
PCB has a few components added on the solder-side, some of which are 
connected with the internal oscillator. By the way, ic5 and ic9 are 
at the bottom of the board, amongst the MC1496s, and _not_ the three 
TL064s in a row at the top of the board.

Tim
 
> 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
> > > > > 
> > > > > 
> > > > > 		
> > > > > __________________________________ 
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> > > > >
> > > >
> > >
> >
>