Doepfer

Hi list,
Having just acquired an A-155 and noticed that it has a small factory-
fitted modification to it, I felt certain that a few weeks ago, 
probably in a discussion on the 154, the purpose of this was briefly 
mentioned. I couldn't find it by searching, so I'm hoping someone out 
there can fill me in on a bit more detail?

Thanks,
Tim

hi tim,
if the mod is a resistor and a capacitor in the a155
control board,then this is the mod i was telling you
about...it's the mod for letting you clock the a155
from an imperfect clock pulse(with not sharp
edges).also,with this mod ,you can step manualy the
sequencer from the tiny step button more
properly(without almost jumping
steps...).but,also,this mod stops the a155 from
running in high audio frequencies!even if you clock
the a155 from an a110 you will notice that,the a155
can't run above a certain speed limit(which is rather
low!)all these are valid only if we're talking about
the same mod,though....
by the way,i removed this mod from two of my a155's
because i want them to be graphic vco's too!
bakis.


--- Tim Stinchcombe
<timothy@tstinchcombe.freeserve.co.uk> wrote:
> Hi list,
> Having just acquired an A-155 and noticed that it
> has a small factory-
> fitted modification to it, I felt certain that a few
> weeks ago, 
> probably in a discussion on the 154, the purpose of
> this was briefly 
> mentioned. I couldn't find it by searching, so I'm
> hoping someone out 
> there can fill me in on a bit more detail?
> 
> Thanks,
> Tim
> 
> 


=====
synthfreak(parallel worlds)
athens-greece
[Doepfer_a100] group owner-moderator

__________________________________________________
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> by the way,i removed this mod from two of my a155's
> because i want them to be graphic vco's too!

How about details? Or maybe you could ask Dieter to describe on the 
DIY page. Or is it already there?

Hi Bakis,
Thanks for the info.

> if the mod is a resistor and a capacitor in the a155
> control board,then this is the mod i was telling you
> about...it's the mod for letting you clock the a155
> from an imperfect clock pulse(with not sharp
> edges).also,with this mod ,you can step manualy the

This is part of what I was after - there is also a wire from the 
control board to the trigger board (it inhibits trig 1 and 2 under 
some conditions), and I was wondering if they were both part of the 
cure for some problem. However, that you say the res & cap were to 
help it with poor clock pulses raises a few questions. I wondered if 
it was for something like this, so I ran a quick simulation of that 
part of the circuit, and got the distinct impression that it actually 
made things *worse*, which made me think it was for some other 
purpose, and that if it was then hopefully the degradation of the 
clock pulse would still be acceptable! (The simulation _did_ show 
that the clock stops running at some point due to the mod, and tied 
in very closely with my measured value - around 800Hz.) I shall look 
at the circuit some more, I may be able to figure it yet!

Tim

> sequencer from the tiny step button more
> properly(without almost jumping
> steps...).but,also,this mod stops the a155 from
> running in high audio frequencies!even if you clock
> the a155 from an a110 you will notice that,the a155
> can't run above a certain speed limit(which is rather
> low!)all these are valid only if we're talking about
> the same mod,though....
> by the way,i removed this mod from two of my a155's
> because i want them to be graphic vco's too!
> bakis.

hi joe,
better ask roland mayer!!!i don't know many things
about electronics and it's better to know what you are
removing...:-)
by the way,i removed this simple mod by using a nails
scizzors for cutting the solder(really!!!)i couldn't
undo the soldering with my soldering iron.....(this
says a lot about my electronics skills...)
bakis.



--- Joe Buechler <buechlerjoe@toadmail.com> wrote:
> > by the way,i removed this mod from two of my
> a155's
> > because i want them to be graphic vco's too!
> 
> How about details? Or maybe you could ask Dieter to
> describe on the 
> DIY page. Or is it already there?
> 
> 


=====
synthfreak(parallel worlds)
athens-greece
[Doepfer_a100] group owner-moderator

__________________________________________________
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Had me more of a think on this...

> if the mod is a resistor and a capacitor in the a155
> control board,then this is the mod i was telling you
> about...it's the mod for letting you clock the a155
> from an imperfect clock pulse(with not sharp

...and I don't think this can be the reason (the clock pulse goes 
through 2 gates anyway, which should sharpen any sluggish pulse up 
plenty!). But I do now believe _this_ must be the reason:

> edges).also,with this mod ,you can step manualy the
> sequencer from the tiny step button more
> properly(without almost jumping
> steps...).

Without the capacitor contact bounce on pushing the clock button 
could well cause it to skip several steps unintentionally. And I 
certainly believe this...

> but,also,this mod stops the a155 from
> running in high audio frequencies!even if you clock
> the a155 from an a110 you will notice that,the a155
> can't run above a certain speed limit(which is rather
> low!)all these are valid only if we're talking about
> the same mod,though....
> by the way,i removed this mod from two of my a155's
> because i want them to be graphic vco's too!

...so if you don't care about the skipping several steps problem, 
snipping through one of the wires to break the link formed by the cap 
& res will let it run at higher speeds. Details for those unsure what 
we're talking about: the 'control board' is small on the right hand 
side of the module, marked 'A-155-4' on underside ('A-155 board 4' on 
top); if you have the mod, on the solderside you'll find a capacitor 
(marked '104') and a 1k resistor (brown, black, red, gold) soldered 
together and bridging two pins of the 4011 IC; cutting or desoldering 
either end of them or where they join will do it!

Tim

> 
> > edges).also,with this mod ,you can step manualy the
> > sequencer from the tiny step button more
> > properly(without almost jumping
> > steps...).
> 

i have an early no-mod 155 and the step button stopped working quite some 
time ago (didn't last long).  i've never been able to find any broken 
connections, i just assumed it was the tiny button contact that died.  while 
we're looking at them, any idea how to troubleshoot this?

any possibility of the mod also coming along to aid in prolonging the life of the 
step button circuit?  

probably a stretch, just throwing it out there..

-psm

On Thu, 13 Mar 2003, Tim Stinchcombe wrote:

> Without the capacitor contact bounce on pushing the clock button
> could well cause it to skip several steps unintentionally. And I
> certainly believe this...

> ...so if you don't care about the skipping several steps problem,
> snipping through one of the wires to break the link formed by the cap
> & res will let it run at higher speeds.

Interesting. I don't believe my 155 actually has this mod. Most of the
time hitting the step button causes my 155 to skip multiple steps, AND
I've never had any problems clocking it at high speeds ;0)

Oh well, I'd probably choose to have it this way given the choice anyway.

-Brandon

___________________________________

The last time anyone listened
to a Bush they wandered through
the desert for 40 years!
___________________________________

They are pretty flimsy little switches.  If indeed it were the switch, it
seems like changing it out might not be that onerous a repair, right?

> -----Original Message-----
> From: ps_minor [mailto:pscottm@hotmail.com]
> Sent: Wednesday, March 12, 2003 9:08 PM
> To: Doepfer_a100@yahoogroups.com
> Subject: [Doepfer_a100] Re: A155 factory-fitted revision
>
>
> >
> > > edges).also,with this mod ,you can step manualy the
> > > sequencer from the tiny step button more
> > > properly(without almost jumping
> > > steps...).
> >
>
> i have an early no-mod 155 and the step button stopped working quite some
> time ago (didn't last long).  i've never been able to find any broken
> connections, i just assumed it was the tiny button contact that
> died.  while
> we're looking at them, any idea how to troubleshoot this?
>
> any possibility of the mod also coming along to aid in prolonging
> the life of the
> step button circuit?
>
> probably a stretch, just throwing it out there..
>
> -psm
>
>
> To unsubscribe from this group, send an email to:
> doepfer_a100-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>

Has anyone tries fitting a toggle switch to a A155 module that would 
allow bypassing the modification?  That way, one could switch between 
the new style A155 sequencer and a graphic VCO.  Seems simple enough 
to do.

--- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe" <timothy@t...> 
wrote:
> Had me more of a think on this...
> 
> > if the mod is a resistor and a capacitor in the a155
> > control board,then this is the mod i was telling you
> > about...it's the mod for letting you clock the a155
> > from an imperfect clock pulse(with not sharp
> 
> ...and I don't think this can be the reason (the clock pulse goes 
> through 2 gates anyway, which should sharpen any sluggish pulse up 
> plenty!). But I do now believe _this_ must be the reason:
> 
> > edges).also,with this mod ,you can step manualy the
> > sequencer from the tiny step button more
> > properly(without almost jumping
> > steps...).
> 
> Without the capacitor contact bounce on pushing the clock button 
> could well cause it to skip several steps unintentionally. And I 
> certainly believe this...
> 
> > but,also,this mod stops the a155 from
> > running in high audio frequencies!even if you clock
> > the a155 from an a110 you will notice that,the a155
> > can't run above a certain speed limit(which is rather
> > low!)all these are valid only if we're talking about
> > the same mod,though....
> > by the way,i removed this mod from two of my a155's
> > because i want them to be graphic vco's too!
> 
> ...so if you don't care about the skipping several steps problem, 
> snipping through one of the wires to break the link formed by the 
cap 
> & res will let it run at higher speeds. Details for those unsure 
what 
> we're talking about: the 'control board' is small on the right hand 
> side of the module, marked 'A-155-4' on underside ('A-155 board 4' 
on 
> top); if you have the mod, on the solderside you'll find a 
capacitor 
> (marked '104') and a 1k resistor (brown, black, red, gold) soldered 
> together and bridging two pins of the 4011 IC; cutting or 
desoldering 

> either end of them or where they join will do it!
> 
> Tim

Hi psm,

> i have an early no-mod 155 and the step button stopped working 
quite some 
> time ago (didn't last long).  i've never been able to find any 
broken 
> connections, i just assumed it was the tiny button contact that 
died.  while 
> we're looking at them, any idea how to troubleshoot this?

If the module still steps OK when a clock signal is applied, then 
your hunch is almost certainly right - the little switch is wired 'in 
parallel' to a transistor, and just manually does what the transistor 
does each time a clock pulse is received (it momentarily connects a 
signal to ground). Thus it appears the switch is no longer making 
contact when pressed. I could describe how to use a short piece of  
wire to test this hypothesis, but you'd have to be _real_ careful to 
connect the right points on the PCB.

> any possibility of the mod also coming along to aid in prolonging 
the life of the 
> step button circuit?  

The only option here would be to mount a beefier switch somewhere, 
which would hopefully last longer than the original. I'm surprised 
that the switch has failed - they look like the sort of thing you 
would find buried behind the faceplate of a VCR for programming it, 
so I would have thought they would have quite a high 'no. of presses' 
life expectancy. Maybe you just got a bad one.

(See my reply to next post on replacing switch.)

Tim

> They are pretty flimsy little switches.  If indeed it were the 
switch, it
> seems like changing it out might not be that onerous a repair, 
right?

It would actually be quite tortuous! The jack sockets corresponding 
to each push-button are mounted on the solder side of the PCB, and 
directly cover the connections and mounting bracket pins of the 
switch. Thus to replace the switch would require removing it's 
associated socket first - a job complicated by the fact that the 
sockets are in such close proximity to each other. The easiest thing 
would probably be to destroy the socket by snapping the plastic, thus 
exposing its pins to ease their removal, change the switch, and put a 
new socket in. Even reaching around the sides of the new socket to 
solder it in place would be tricky and require a small soldering iron 
bit! (There is so little room in fact that in a few instances the 
mounting bracket for the switch is used to route the signal coming in 
from the socket - very cunning!)

Definitely not one for the faint-hearted!

Tim

Hi Kevin,

> Has anyone tries fitting a toggle switch to a A155 module that 
would 
> allow bypassing the modification?  That way, one could switch 
between 
> the new style A155 sequencer and a graphic VCO.  Seems simple 
enough 
> to do.

No, but I've half a mind to do it (it would be interesting to see how 
fast it will run without the mod!). There's plenty of space to the 
left of the 'trigger outputs' to mount a simple on/off toggle switch: 
desolder the join between the resistor and capacitor, then add a 
single wire from the end of each to the separate terminals of the 
switch. Done.

Tim


> 
> --- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe" 
<timothy@t...> 
> wrote:
> > Had me more of a think on this...
> > 
> > > if the mod is a resistor and a capacitor in the a155
> > > control board,then this is the mod i was telling you
> > > about...it's the mod for letting you clock the a155
> > > from an imperfect clock pulse(with not sharp
> > 
> > ...and I don't think this can be the reason (the clock pulse goes 
> > through 2 gates anyway, which should sharpen any sluggish pulse 
up 
> > plenty!). But I do now believe _this_ must be the reason:
> > 
> > > edges).also,with this mod ,you can step manualy the
> > > sequencer from the tiny step button more
> > > properly(without almost jumping
> > > steps...).
> > 
> > Without the capacitor contact bounce on pushing the clock button 
> > could well cause it to skip several steps unintentionally. And I 
> > certainly believe this...
> > 
> > > but,also,this mod stops the a155 from
> > > running in high audio frequencies!even if you clock
> > > the a155 from an a110 you will notice that,the a155
> > > can't run above a certain speed limit(which is rather
> > > low!)all these are valid only if we're talking about
> > > the same mod,though....
> > > by the way,i removed this mod from two of my a155's
> > > because i want them to be graphic vco's too!
> > 
> > ...so if you don't care about the skipping several steps problem, 
> > snipping through one of the wires to break the link formed by the 
> cap 
> > & res will let it run at higher speeds. Details for those unsure 
> what 
> > we're talking about: the 'control board' is small on the right 
hand 
> > side of the module, marked 'A-155-4' on underside ('A-155 board 
4' 
> on 
> > top); if you have the mod, on the solderside you'll find a 
> capacitor 
> > (marked '104') and a 1k resistor (brown, black, red, gold) 
soldered 

> > together and bridging two pins of the 4011 IC; cutting or 
> desoldering 
> > either end of them or where they join will do it!
> > 
> > Tim

hi tom,
by comparing my moded and unmoded a155's i saw that
the moded a155's really can be clocked even from saw
waves and run normally(that's a bad thing,isn't
it???)and,also they step correctly when you manually
step them with the step button,not as the unmoded a155
do...
bakis.


--- Tim Stinchcombe
<timothy@tstinchcombe.freeserve.co.uk> wrote:
> Hi Bakis,
> Thanks for the info.
> 
> > if the mod is a resistor and a capacitor in the
> a155
> > control board,then this is the mod i was telling
> you
> > about...it's the mod for letting you clock the
> a155
> > from an imperfect clock pulse(with not sharp
> > edges).also,with this mod ,you can step manualy
> the
> 
> This is part of what I was after - there is also a
> wire from the 
> control board to the trigger board (it inhibits trig
> 1 and 2 under 
> some conditions), and I was wondering if they were
> both part of the 
> cure for some problem. However, that you say the res
> & cap were to 
> help it with poor clock pulses raises a few
> questions. I wondered if 
> it was for something like this, so I ran a quick
> simulation of that 
> part of the circuit, and got the distinct impression
> that it actually 
> made things *worse*, which made me think it was for
> some other 
> purpose, and that if it was then hopefully the
> degradation of the 
> clock pulse would still be acceptable! (The
> simulation _did_ show 
> that the clock stops running at some point due to
> the mod, and tied 
> in very closely with my measured value - around
> 800Hz.) I shall look 
> at the circuit some more, I may be able to figure it
> yet!
> 
> Tim
> 
> 
> > sequencer from the tiny step button more
> > properly(without almost jumping
> > steps...).but,also,this mod stops the a155 from
> > running in high audio frequencies!even if you
> clock
> > the a155 from an a110 you will notice that,the
> a155
> > can't run above a certain speed limit(which is
> rather
> > low!)all these are valid only if we're talking
> about
> > the same mod,though....
> > by the way,i removed this mod from two of my
> a155's
> > because i want them to be graphic vco's too!
> > bakis.
> 
> 
> 


=====
synthfreak(parallel worlds)
athens-greece
[Doepfer_a100] group owner-moderator

__________________________________________________
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took another look..you're right, would be torturous, for me anyway.   i'll just 
continue on w/o the button..  not a huge inconvenience.  plenty else to jog 
around with.

thanks for your insight!

-psm

> 
> It would actually be quite tortuous! The jack sockets corresponding 
> to each push-button are mounted on the solder side of the PCB, and 
> directly cover the connections and mounting bracket pins of the 
> switch. Thus to replace the switch would require removing it's 
> associated socket first - a job complicated by the fact that the 
> sockets are in such close proximity to each other. The easiest thing 
> would probably be to destroy the socket by snapping the plastic, thus 
> exposing its pins to ease their removal, change the switch, and put a 
> new socket in. Even reaching around the sides of the new socket to 
> solder it in place would be tricky and require a small soldering iron 
> bit! (There is so little room in fact that in a few instances the 
> mounting bracket for the switch is used to route the signal coming in 
> from the socket - very cunning!)
> 
> Definitely not one for the faint-hearted!
> 
> Tim

hi bakis,

well i'm glad you mention that.  i just double checked and when no clock is 
plugged into the clock input, the botton does not work regardless of hitting 
start first.  

also, the button does not interupt the clock signal like it used to.  in fact, forgot 
i used to do this..when in graphic osc mode, would sometimes use the button 
to blip-out the sound coming from the 155 since it interupts the clock, useful 
for a short wave transmission type of sound.  

if any missing feature could inspire me to fix the button, that is it.

-psm






--- In Doepfer_a100@yahoogroups.com, Bakis Sirros <
synth_freak_2000@y...> wrote:

> hi psm,
> i think this is obvious but,have you started the a155
> before hitting the step button?you need to start the
> a155 first(hit the start button) and then manually
> step it.
> bakis.
> 
> 
> --- unknown freak <cgraef@n...> wrote:
> > They are pretty flimsy little switches.  If indeed
> > it were the switch, it
> > seems like changing it out might not be that onerous
> > a repair, right?
> > 
> > > -----Original Message-----
> > > From: ps_minor [mailto:pscottm@h...]
> > > Sent: Wednesday, March 12, 2003 9:08 PM
> > > To: Doepfer_a100@yahoogroups.com
> > > Subject: [Doepfer_a100] Re: A155 factory-fitted
> > revision
> > >
> > >
> > > >
> > > > > edges).also,with this mod ,you can step
> > manualy the
> > > > > sequencer from the tiny step button more
> > > > > properly(without almost jumping
> > > > > steps...).
> > > >
> > >
> > > i have an early no-mod 155 and the step button
> > stopped working quite some
> > > time ago (didn't last long).  i've never been able
> > to find any broken
> > > connections, i just assumed it was the tiny button
> > contact that
> > > died.  while
> > > we're looking at them, any idea how to
> > troubleshoot this?
> > >
> > > any possibility of the mod also coming along to
> > aid in prolonging
> > > the life of the
> > > step button circuit?
> > >
> > > probably a stretch, just throwing it out there..
> > >
> > > -psm
> > >
> > >
> > > To unsubscribe from this group, send an email to:
> > > doepfer_a100-unsubscribe@yahoogroups.com
> > >
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> > >
> > >
> > >
> > 
> > 
> > 
> 
> 
> =====
> synthfreak(parallel worlds)
> athens-greece
> [Doepfer_a100] group owner-moderator
> 
> __________________________________________________
> Do you Yahoo!?
> Yahoo! Web Hosting - establish your business online
> http://webhosting.yahoo.com

hi psm,
i think this is obvious but,have you started the a155
before hitting the step button?you need to start the
a155 first(hit the start button) and then manually
step it.
bakis.


--- unknown freak <cgraef@nyc.rr.com> wrote:
> They are pretty flimsy little switches.  If indeed
> it were the switch, it
> seems like changing it out might not be that onerous
> a repair, right?
> 
> > -----Original Message-----
> > From: ps_minor [mailto:pscottm@hotmail.com]
> > Sent: Wednesday, March 12, 2003 9:08 PM
> > To: Doepfer_a100@yahoogroups.com
> > Subject: [Doepfer_a100] Re: A155 factory-fitted
> revision
> >
> >
> > >
> > > > edges).also,with this mod ,you can step
> manualy the
> > > > sequencer from the tiny step button more
> > > > properly(without almost jumping
> > > > steps...).
> > >
> >
> > i have an early no-mod 155 and the step button
> stopped working quite some
> > time ago (didn't last long).  i've never been able
> to find any broken
> > connections, i just assumed it was the tiny button
> contact that
> > died.  while
> > we're looking at them, any idea how to
> troubleshoot this?
> >
> > any possibility of the mod also coming along to
> aid in prolonging
> > the life of the
> > step button circuit?
> >
> > probably a stretch, just throwing it out there..
> >
> > -psm
> >
> >
> > To unsubscribe from this group, send an email to:
> > doepfer_a100-unsubscribe@yahoogroups.com
> >
> >
> >
> > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> >
> >
> >
> 
> 
> 


=====
synthfreak(parallel worlds)
athens-greece
[Doepfer_a100] group owner-moderator

__________________________________________________
Do you Yahoo!?
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Hi list
That´t what I was thinking about too. If cutting one wire (or 
connection) is all you need to disable the modification then you could 
as well build a toggle switch in between and solder it to the mod with a 
few inches of wire.
Does anyone possess both the old and the new A-155? Bakis? If so, could 
you please upload photos of both PCBs for comparison? Or can one see the 
factory fitted mod immediately?

Paul

btw, Tim, thanks for uploading the pics of the a-140 & A-150 
modifications. I´ll try to mod one ADSR soon.



code_pig wrote:
Has anyone tries fitting a toggle switch to a A155 module that would
allow bypassing the modification?  That way, one could switch between
the new style A155 sequencer and a graphic VCO.  Seems simple enough
to do.

Tim wrote:
No, but I've half a mind to do it (it would be interesting to see how
fast it will run without the mod!). There's plenty of space to the
left of the 'trigger outputs' to mount a simple on/off toggle switch:
desolder the join between the resistor and capacitor, then add a
single wire from the end of each to the separate terminals of the
switch. Done.

Tim

HI PAUL,
IF YOU FOLLOW TIM'S DESCRIPTION YOU CAN FIND THE MOD
VERY EASILLY...
BAKIS.


--- Paul Schulz <dasfonk@web.de> wrote:
>   Hi list
> That�t what I was thinking about too. If cutting one
> wire (or 
> connection) is all you need to disable the
> modification then you could 
> as well build a toggle switch in between and solder
> it to the mod with a 
> few inches of wire.
> Does anyone possess both the old and the new A-155?
> Bakis? If so, could 
> you please upload photos of both PCBs for
> comparison? Or can one see the 
> factory fitted mod immediately?
> 
> Paul
> 
> btw, Tim, thanks for uploading the pics of the a-140
> & A-150 
> modifications. I�ll try to mod one ADSR soon.
> 
> 
> 
> code_pig wrote:
> Has anyone tries fitting a toggle switch to a A155
> module that would
> allow bypassing the modification?  That way, one
> could switch between
> the new style A155 sequencer and a graphic VCO. 
> Seems simple enough
> to do.
> 
> Tim wrote:
> No, but I've half a mind to do it (it would be
> interesting to see how
> fast it will run without the mod!). There's plenty
> of space to the
> left of the 'trigger outputs' to mount a simple
> on/off toggle switch:
> desolder the join between the resistor and
> capacitor, then add a
> single wire from the end of each to the separate
> terminals of the
> switch. Done.
> 
> Tim
> 
> 


=====
synthfreak(parallel worlds)
athens-greece
[Doepfer_a100] group owner-moderator

__________________________________________________
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