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A-126 Malfunction

A-126 Malfunction

2019-02-20 by a11@live.nl

Hello to you all,

[What a coincidence with Rigo's broken A-126!].


Today I started to try to fix my old A-126 by just replace some suspected components.
Because the Shift and Mix and Up-Down outputs do not work properly at all; for you just hear some changes in sound, when turning the knobs. I mean you do not hear up and down sounds at the same time. And it also does not go/sound from down to up and vice versa.
And you do not hear any mix sounds at the Mix output.
And the Up and Down outputs sound the same.

I started to replace IC 5 (TL064).
And now you can hear the sound goes from down to up (up-shifting part), but no down-shifting sound to hear.
And the Up and Down outputs still sound the same.

And now I do not know which components I should replace next.
Is there somebody who please can give me a hint, for I do can solder very well, so I won't dissapoint you.

Benny


AW: [Doepfer_a100] A-126 Malfunction

2019-02-20 by yahoo@doepfer.de

As already mentioned in the other email the A-126 is a very complex circuit.
But if the up shift is working there is some chance that only the adder for
the down shifting is faulty. It's built around the TL084 between the two
ring modulators MC1496. If replacing the TL084 does not help one has to
track the circuit with an oscilloscope to find out what's wrong. Maybe the
trimming potentiometer for the down adjustment is broken.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Mittwoch, 20. Februar 2019 01:29
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] A-126 Malfunction
>
>
> Hello to you all,
>
> [What a coincidence with Rigo's broken A-126!].
>
> Today I started to try to fix my old A-126 by just replace some
> suspected components.
> Because the Shift and Mix and Up-Down outputs do not work
> properly at all; for you just hear some changes in sound, when
> turning the knobs. I mean you do not hear up and down sounds at
> the same time. And it also does not go/sound from down to up and
> vice versa.
> And you do not hear any mix sounds at the Mix output.
> And the Up and Down outputs sound the same.
>
> I started to replace IC 5 (TL064).
> And now you can hear the sound goes from down to up (up-shifting
> part), but no down-shifting sound to hear.
> And the Up and Down outputs still sound the same.
>
> And now I do not know which components I should replace next.
> Is there somebody who please can give me a hint, for I do can
> solder very well, so I won't dissapoint you.
>
> Benny

Re: AW: [Doepfer_a100] A-126 Malfunction

2019-02-20 by a11@live.nl

Thank you for your reply, Dieter.
Today I replaced the TL084 and indeed I could now hear down-sounds, but not at every Shift value/level. It's irregular.
And the down and up outputs are still equal (same sound).

Next I will look for a new trimming potentiometer for the down adjustment. I think it's the P18 / 5K.
If that does not help I will replace the other IC's except the CEM. After that I will replace the caps, if that does not help.
I'm not in a hurry, and I have lots of other modules to play with, although the A126 is one of the sweetest to play with.


All the best
Ben


---In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote :

As already mentioned in the other email the A-126 is a very complex circuit.
But if the up shift is working there is some chance that only the adder for
the down shifting is faulty. It's built around the TL084 between the two
ring modulators MC1496. If replacing the TL084 does not help one has to
track the circuit with an oscilloscope to find out what's wrong. Maybe the
trimming potentiometer for the down adjustment is broken.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Mittwoch, 20. Februar 2019 01:29
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] A-126 Malfunction
>
>
> Hello to you all,
>
> [What a coincidence with Rigo's broken A-126!].
>
> Today I started to try to fix my old A-126 by just replace some
> suspected components.
> Because the Shift and Mix and Up-Down outputs do not work
> properly at all; for you just hear some changes in sound, when
> turning the knobs. I mean you do not hear up and down sounds at
> the same time. And it also does not go/sound from down to up and
> vice versa.
> And you do not hear any mix sounds at the Mix output.
> And the Up and Down outputs sound the same.
>
> I started to replace IC 5 (TL064).
> And now you can hear the sound goes from down to up (up-shifting
> part), but no down-shifting sound to hear.
> And the Up and Down outputs still sound the same.
>
> And now I do not know which components I should replace next.
> Is there somebody who please can give me a hint, for I do can
> solder very well, so I won't dissapoint you.
>
> Benny

AW: AW: [Doepfer_a100] A-126 Malfunction

2019-02-21 by yahoo@doepfer.de

Hello Ben,

that's strange. The level of the up/down sounds should not depends upon the
shift frequency. This points to a problem with the quadrature oscillator
(i.e. that the sine and cosine are not stable/present at each frequency). I
don't think that it's a problem of the adder/subtractor for the up/down
generation. I'd recommend to measure the sine and cosine of the oscillator
while the frequency is changed.

I also don't think that capacitors are responsible. That's very uncommon
(but who knows ...). In the first place I'd replace the integrated circuits
and then the (trimming and normal) potentiometers.

And also the correct adjustment is very important. I remember that it took
up to one hour to do carry out all the adjustments of the A-126.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Mittwoch, 20. Februar 2019 23:35
> An: Doepfer_a100@yahoogroups.com
> Betreff: Re: AW: [Doepfer_a100] A-126 Malfunction
>
>
> Thank you for your reply, Dieter.
> Today I replaced the TL084 and indeed I could now hear
> down-sounds, but not at every Shift value/level. It's irregular.
> And the down and up outputs are still equal (same sound).
>
> Next I will look for a new trimming potentiometer for the down
> adjustment. I think it's the P18 / 5K.
> If that does not help I will replace the other IC's except the
> CEM. After that I will replace the caps, if that does not help.
>
> I'm not in a hurry, and I have lots of other modules to play
> with, although the A126 is one of the sweetest to play with.
>
> All the best
> Ben
>
>
>
>
> ---In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote :
>
>
> As already mentioned in the other email the A-126 is a very
> complex circuit.
> But if the up shift is working there is some chance that only the
> adder for
> the down shifting is faulty. It's built around the TL084 between the two
> ring modulators MC1496. If replacing the TL084 does not help one has to
> track the circuit with an oscilloscope to find out what's wrong. Maybe the
> trimming potentiometer for the down adjustment is broken.
>
> Best wishes
> Dieter Doepfer
>
>
> > -----Ursprüngliche Nachricht-----
> > Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> > Gesendet: Mittwoch, 20. Februar 2019 01:29
> > An: Doepfer_a100@yahoogroups.com
> > Betreff: [Doepfer_a100] A-126 Malfunction
> >
> >
> > Hello to you all,
> >
> > [What a coincidence with Rigo's broken A-126!].
> >
> > Today I started to try to fix my old A-126 by just replace some
> > suspected components.
> > Because the Shift and Mix and Up-Down outputs do not work
> > properly at all; for you just hear some changes in sound, when
> > turning the knobs. I mean you do not hear up and down sounds at
> > the same time. And it also does not go/sound from down to up and
> > vice versa.
> > And you do not hear any mix sounds at the Mix output.
> > And the Up and Down outputs sound the same.
> >
> > I started to replace IC 5 (TL064).
> > And now you can hear the sound goes from down to up (up-shifting
> > part), but no down-shifting sound to hear.
> > And the Up and Down outputs still sound the same.
> >
> > And now I do not know which components I should replace next.
> > Is there somebody who please can give me a hint, for I do can
> > solder very well, so I won't dissapoint you.
> >
> > Benny
>
>
>
>

Re: A-126 Malfunction

2019-02-22 by a11@live.nl

Forgot to say that I do not have an oscilloscope to measure the circuit.
I do not hope the CEM3382 is broken, for it is hard to find.

And if the correct adjustment is very important, I will try to do that first. The adjustment I ever have made, is to reduce the sine bleeding with four of those trimmers. Maybe I did something wrong then.

But today I scratched with a wooden stick all over the solder part, while the module was playing and discover a loose solder part. It was pin 7 from IC2/TL064 close to the Audio Input. That pin is connected with R15.
Fixing the connection only result in a louder sound.

Since my A126 has mostly ic's without a socket, it will take much time to replace them. But it is worthwhile. And I think it is always good to replace old components, for they say that they do not perform optimal anymore.
On the other hand, I always hated the bleeding sine of this module. If the upcoming new Freq Shifter has no bleeding I'll have one. Because a FS is special, it is very funny.

AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-22 by yahoo@doepfer.de

So the A-126 seems to be very old as we use sockets for integrated circuits
since nearly 20 years because it simplifies the service in case of a faulty
integrated circuit clearly.
Let's hope that the mentioned interruption is the only problem (apart from
re-adjustment).
The planned new frequency shifter module will be equipped with a squelch
circuit (combination of envelope follower and VCA) that can be used to avoid
the bleeding of the multipliers. But with optimal adjustment the bleed of
the old A-126  should be better than about -50dB. So far the new FS is still
in the development state and I have no release date available. It's a very
special module which I do mainly for myself and I don't expect large sales.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Freitag, 22. Februar 2019 01:44
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-126 Malfunction
>
>
> Forgot to say that I do not have an oscilloscope to measure the circuit.
> I do not hope the CEM3382 is broken, for it is hard to find.
>
> And if the correct adjustment is very important, I will try to do
> that first. The adjustment I ever have made, is to reduce the
> sine bleeding with four of those trimmers. Maybe I did something
> wrong then.
>
> But today I scratched with a wooden stick all over the solder
> part, while the module was playing and discover a loose solder
> part. It was pin 7 from IC2/TL064 close to the Audio Input. That
> pin is connected with R15.
> Fixing the connection only result in a louder sound.
>
> Since my A126 has mostly ic's without a socket, it will take much
> time to replace them. But it is worthwhile. And I think it is
> always good to replace old components, for they say that they do
> not perform optimal anymore.
> On the other hand, I always hated the bleeding sine of this
> module. If the upcoming new Freq Shifter has no bleeding I'll
> have one. Because a FS is special, it is very funny.

Re: A-126 Malfunction

2019-02-22 by rigo.schoeters@yahoo.com

> I do not hope the CEM3382 is broken, for it is hard to find.

Older versions of the A-131 have the differently named but identical circuit PA382, so buy some if some pop up for sale.

On my A-126 the only chip that was in a socket was that CEM, so probably it is an older model as well.

Now that I got a working A-126 and a broken A-131 I should treat myself to some more VCAs ... maybe the A-135-4 will do as birthday present

Re: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-22 by a11@live.nl

Yes, I bought it very long ago. It also has 2 caps, 1 diode and 1 resistor on the solder side; so they do not go through the holes.

But wait a minute, Dieter, hold it. You said:
"It's a very special module which I do mainly for myself and I don't expect large sales".
Do you mean that the price will be very high and that's why you don't expect large sales?
The old one was I think 180 euro.

Ben



---In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote :

So the A-126 seems to be very old as we use sockets for integrated circuits
since nearly 20 years because it simplifies the service in case of a faulty
integrated circuit clearly.
Let's hope that the mentioned interruption is the only problem (apart from
re-adjustment).
The planned new frequency shifter module will be equipped with a squelch
circuit (combination of envelope follower and VCA) that can be used to avoid
the bleeding of the multipliers. But with optimal adjustment the bleed of
the old A-126 should be better than about -50dB. So far the new FS is still
in the development state and I have no release date available. It's a very
special module which I do mainly for myself and I don't expect large sales.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Freitag, 22. Februar 2019 01:44
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-126 Malfunction
>
>
> Forgot to say that I do not have an oscilloscope to measure the circuit.
> I do not hope the CEM3382 is broken, for it is hard to find.
>
> And if the correct adjustment is very important, I will try to do
> that first. The adjustment I ever have made, is to reduce the
> sine bleeding with four of those trimmers. Maybe I did something
> wrong then.
>
> But today I scratched with a wooden stick all over the solder
> part, while the module was playing and discover a loose solder
> part. It was pin 7 from IC2/TL064 close to the Audio Input. That
> pin is connected with R15.
> Fixing the connection only result in a louder sound.
>
> Since my A126 has mostly ic's without a socket, it will take much
> time to replace them. But it is worthwhile. And I think it is
> always good to replace old components, for they say that they do
> not perform optimal anymore.
> On the other hand, I always hated the bleeding sine of this
> module. If the upcoming new Freq Shifter has no bleeding I'll
> have one. Because a FS is special, it is very funny.

Re: A-126 Malfunction

2019-02-22 by a11@live.nl

Yes, thank you Rigo. I saw it in your thread about the PA382.
And you are lucky you had one in an old module and lucky again you do not have to solder it. And lucky again, that your birthday is coming soon.

Does yours also have some parts on the solder side?

Ben



---In Doepfer_a100@yahoogroups.com, <rigo.schoeters@...> wrote :

Show quoted textHide quoted text
> I do not hope the CEM3382 is broken, for it is hard to find.

Older versions of the A-131 have the differently named but identical circuit PA382, so buy some if some pop up for sale.

On my A-126 the only chip that was in a socket was that CEM, so probably it is an older model as well.

Now that I got a working A-126 and a broken A-131 I should treat myself to some more VCAs ... maybe the A-135-4 will do as birthday present

Re: A-126 Malfunction

2019-02-23 by rigo.schoeters@yahoo.com

> Does yours also have some parts on the solder side?

4 parts are soldered at the back.

AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-25 by yahoo@doepfer.de

It's too early to speak about prices. We can calculate the module not before
the development has been finished and the quantity of the first production
run has been defined. But in any case it will be more expensive than the old
frequency shifter because of the additional functions.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> But wait a minute, Dieter, hold it. You said:
> "It's a very special module which I do mainly for myself and I
> don't expect large sales".
> Do you mean that the price will be very high and that's why you
> don't expect large sales?
> The old one was I think 180 euro.
>
>
> Ben

AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-25 by yahoo@doepfer.de

I took a look at the old A-126 documentation. The additional parts have been
added to stabilize the internal voltages (+9V, -9V). You will find probably
two electrolytic capacitors (one soldered between GND and +9V, another
between GND and -9V) and a Schottky diode (soldered between GND and +9V to
prevent from the so-called latch-up effect). And there may be an additional
Z-diode (5V1 or 5V6) that limits the control voltage for the CEM3382 to
about 5V, and a 1nF capacitor that prevents high frequency noise in the
quadrature VCO circuit.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Samstag, 23. Februar 2019 10:17
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-126 Malfunction
>
>
>
>
> > Does yours also have some parts on the solder side?
>
>
> 4 parts are soldered at the back.

Re: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-25 by a11@live.nl

But strange that one of my additional parts is a resistor, that has been soldered right at the same place of another resistor, but on the solder side.
This resistor is R94/22K near the Up Output on the edge.
The additional resistor is, I think, 10k; it is brown-black without a multiplier color.

Should I remove it?

AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-26 by yahoo@doepfer.de

Probably the range of the trimming potentiometer P18 (- adjust) was not
sufficient because P18 and R94 are connected in series. The effective value
of R94 (normally 22k) has been probably reduced by soldering a second
resistor in parallel to obtain the correct adjustment for P18. But I don't
think that the additional resistor is 10k because this would result in about
6,8k which is totally different from the 22k. I cannot imagine that the
value for R94 is that far away from the correct value for the P18
adjustment. I'd expect a higher value for the additional resistor (in the
47k...100k range).

I'd not recommend to remove the resistor as I think it has been added
intentionally.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Montag, 25. Februar 2019 23:02
> An: Doepfer_a100@yahoogroups.com
> Betreff: Re: AW: [Doepfer_a100] Re: A-126 Malfunction
>
>
> But strange that one of my additional parts is a resistor, that
> has been soldered right at the same place of another resistor,
> but on the solder side.
> This resistor is R94/22K near the Up Output on the edge.
> The additional resistor is, I think, 10k; it is brown-black
> without a multiplier color.
>
> Should I remove it?

Re: AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-26 by a11@live.nl

Fine Dieter, then I will leave that.
I could see later on a picture that the multiplier of the additional resistor is yellow, so its value would be 100K. The picture I have made years ago.

Now I have replaced IC7/MC1496, which have a socket, with a fresh one. But there were no changes.

So now The CEM3382 then.
Hereby I am told by ALFA RPAR that I can try the AS3360 [for making repair], because they have no 3382.
Can I try it, Dieter? It is here:


AW: AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-27 by yahoo@doepfer.de

The AS3360 is totally different compared to CEM3382/PA382 (e.g. 14 pin
package instead of 8 pin). I don't think that it will work even if you would
built kind of an adapter board.
I think you will have to look for a CEM3382/PA382 e.g. on Ebay. But before
that I'd check if the quadrature VCO is working (sine/cosine on Y1/Y2). Even
if the VCO is not working it is not 100% sure that replacing the CEM3382
will solve the problem. It could be also another fault, that causes the
malfunction of the VCO. As already mentioned the A-126 is a very complex
circuit and the repair requires a lot of electronic experience and
understanding of the circuit (dome filter, quadrature VCO, ring modulators,
mixer ...).

You may also send in the module for repair. But you have to keep in mind
that we also have to search also for a CEM3382 provided that it is faulty so
that the repair may become a bit expensive.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> Fine Dieter, then I will leave that.
> I could see later on a picture that the multiplier of the
> additional resistor is yellow, so its value would be 100K. The
> picture I have made years ago.
>
>
>
> Now I have replaced IC7/MC1496, which have a socket, with a fresh
> one. But there were no changes.
>
>
> So now The CEM3382 then.
> Hereby I am told by ALFA RPAR that I can try the AS3360 [for
> making repair], because they have no 3382.
>
> Can I try it, Dieter? It is here:
> http://www.alfarzpp.lv/eng/sc/AS3360.php

Re: AW: AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-27 by a11@live.nl

Sorry, but I forgot to mention that I did the readjustment [without scope], but things stay the same. But it was remarkable that:

1. only the Y2 bal. could minimize the signal appearing; but it did it very well.
2. the signal did not get as high as before, when turning fully with the Shift knob. And it hears like the signal is not a real sinus/cosinus; its a bit different like before.

Today I remembered I tried to make the simple A126_A143_9_connection years ago. But something went wrong and I decided to cancel the mod, because other things got priority.

And now I wonder if I try it again succesfully, that I do not need the internal osc.
And if it then works well with the extern osc of A143_9, can one say that the CEM was broken?

Thanks for offer repairing, but I want to challenge it, otherwise I just wait for the upcoming new FS.

AW: AW: AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-28 by yahoo@doepfer.de

If the frequency shifter works with an external quadrature VCO (A-143-9 or
A-110-4) it clear that the internal CEM3382 based VCO is faulty.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> Sorry, but I forgot to mention that I did the readjustment
> [without scope], but things stay the same. But it was remarkable that:
>
>
>
> 1. only the Y2 bal. could minimize the signal appearing; but it
> did it very well.
> 2. the signal did not get as high as before, when turning fully
> with the Shift knob. And it hears like the signal is not a real
> sinus/cosinus; its a bit different like before.
>
> Today I remembered I tried to make the simple
> A126_A143_9_connection years ago. But something went wrong and I
> decided to cancel the mod, because other things got priority.
>
> And now I wonder if I try it again succesfully, that I do not
> need the internal osc.
>
> And if it then works well with the extern osc of A143_9, can one
> say that the CEM was broken?
>
>
> Thanks for offer repairing, but I want to challenge it, otherwise
> I just wait for the upcoming new FS.
>

Re: AW: AW: AW: AW: [Doepfer_a100] Re: A-126 Malfunction

2019-02-28 by a11@live.nl

Fine, Dieter, and thank you for all the advice.

Then I go futher to replace the ic's.
Today I did IC3. And again nothing have changed.
The next one will be IC8, tomorrow or next week.

Good luck


---In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote :

If the frequency shifter works with an external quadrature VCO (A-143-9 or
A-110-4) it clear that the internal CEM3382 based VCO is faulty.

Best wishes
Dieter Doepfer
Show quoted textHide quoted text
> Sorry, but I forgot to mention that I did the readjustment
> [without scope], but things stay the same. But it was remarkable that:
>
>
>
> 1. only the Y2 bal. could minimize the signal appearing; but it
> did it very well.
> 2. the signal did not get as high as before, when turning fully
> with the Shift knob. And it hears like the signal is not a real
> sinus/cosinus; its a bit different like before.
>
> Today I remembered I tried to make the simple
> A126_A143_9_connection years ago. But something went wrong and I
> decided to cancel the mod, because other things got priority.
>
> And now I wonder if I try it again succesfully, that I do not
> need the internal osc.
>
> And if it then works well with the extern osc of A143_9, can one
> say that the CEM was broken?
>
>
> Thanks for offer repairing, but I want to challenge it, otherwise
> I just wait for the upcoming new FS.
>

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