Vintage Synth Repair

does anyone know how to find the test points on the arp odyssey mk1?
i'm hoping to do the calibration.

also, i'm still not really good at reading circuit diagram vrs the
circuit board itself and i'm trying to make the noise generator
modification. can anyone give me any more direction on where the zener
diode goes?

thanks,
johnny

On the subject of arp stuff..Ive been thinking of
getting an Arp Omni but how come nearly every single
one I see is broken, not working, in need of repair
etc?

Whats the story?

Phil.




      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

At 17:08 Uhr +0100 08.05.2008, Philip wrote:
> On the subject of arp stuff..Ive been thinking of
> getting an Arp Omni but how come nearly every single
> one I see is broken, not working, in need of repair
> etc?

There has been some discussion about this in the past few days. Some
components inside the Omni are prone to failure.

Here is a good description of the two typical problems:

http://www.oldcrows.net/~oldcrow/synth/tips.txt

The Omni uses quite a number of series 4000 CMOS chips; and also a huge
number of tantalum caps. The one I'm currently trying to fix had a number
of those chips and a number of those caps blown. The chips are very cheap;
and I substituted electrolytic caps for the tantalum caps in the gating
circuit. This got me about halfway to a working Omni - all voices produce
sound now; and the gating circuits basically work (there are still some
other problems, though).

Anyway, it's a totally great sounding poly ensemble synth. The sound of
those divide-down synths certainly is something special.

The parts are cheap and mostly generic. I'm still learning all this stuff
but I consider the Omni one of the easier to understand synths,
circuit-wise. So if you want to learn to fix something a cheap non-working
Omni might be a ticket.

-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

Cool...thanks for that...yeh I seem to remember
something about the tants being a problem in that
model.

Well I managed to fix a dead Quadra so I feel I could
have a go at one of these..:)

Phil.


--- Malte Rogacki <gacki@...> wrote:

> At 17:08 Uhr +0100 08.05.2008, Philip wrote:
> > On the subject of arp stuff..Ive been thinking of
> > getting an Arp Omni but how come nearly every
> single
> > one I see is broken, not working, in need of
> repair
> > etc?
> 
> There has been some discussion about this in the
> past few days. Some
> components inside the Omni are prone to failure.
> 
> Here is a good description of the two typical
> problems:
> 
> http://www.oldcrows.net/~oldcrow/synth/tips.txt
> 
> The Omni uses quite a number of series 4000 CMOS
> chips; and also a huge
> number of tantalum caps. The one I'm currently
> trying to fix had a number
> of those chips and a number of those caps blown. The
> chips are very cheap;
> and I substituted electrolytic caps for the tantalum
> caps in the gating
> circuit. This got me about halfway to a working Omni
> - all voices produce
> sound now; and the gating circuits basically work
> (there are still some
> other problems, though).
> 
> Anyway, it's a totally great sounding poly ensemble
> synth. The sound of
> those divide-down synths certainly is something
> special.
> 
> The parts are cheap and mostly generic. I'm still
> learning all this stuff
> but I consider the Omni one of the easier to
> understand synths,
> circuit-wise. So if you want to learn to fix
> something a cheap non-working
> Omni might be a ticket.
> 
> -- 
> Malte Rogacki gacki@...
>
----------------------------------------------------------------------------
> "Don't forget to TURN ON THE SYNTHESIZER. Often this
> is the reason why you
>  get no sound out of it." (ARP 2600 Owner's Manual)
>
----------------------------------------------------------------------------
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

At 15:45 Uhr +0000 08.05.2008, Johnny wrote:
> does anyone know how to find the test points on the arp odyssey mk1?
> i'm hoping to do the calibration.

The calibration is described pretty well in the service manual and most of
it doesn't require to know the test points. The calibration notes usually
give very detailed description where to connect the test equipment.

> also, i'm still not really good at reading circuit diagram vrs the
> circuit board itself and i'm trying to make the noise generator
> modification. can anyone give me any more direction on where the zener
> diode goes?

My uderstanding is that the zener diode modification applies to the A-II
board variants and not to the A-I board. Usually the mk1 will have a A-I
board, I think.


-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

At 20:35 Uhr +0100 08.05.2008, Philip wrote:
> Cool...thanks for that...yeh I seem to remember
> something about the tants being a problem in that
> model.
>
> Well I managed to fix a dead Quadra so I feel I could
> have a go at one of these..:)


http://peterunderdog.com/arp/repair.html

is another starting point.

The beauty of the Omni is that large parts of it can be "debugged" one
after another.

Check power supply and power on boards.

Check master oscillator.

Check divide-down circuitry.

Check gating circuits.

and so on.

Repair-wise it's really a "one step at a time" synth; and that IMHO makes
fixing it a bit easier than synths with a myriad on dependent functions.

-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

hi Philip, i have Omni schematics & other info that might be useful for 
you on the "ARP Omni Resource Page"

http://peterunderdog.com/arp/

i did a lot of work on my Omni but it still has issues that keep it from 
sounding as good as the demo recording - can't get the String Controller 
to work right, and half of the bass section (16' bass synth and string 
section bass) doesn't work...the tants are a definite problem - i 
replaced mine w/aluminum electrolytics, which i later found out is 
probably not a good idea (i.e., should replace w/new tants)...however, 
it sounds better now than it did w/the old tants and an old weird note 
sustain problem that existed when i got the synth in "the 80s" (i.e., 
1980 :-) was apparently fixed in the process

if you find out any interesting info, let me know & i'll post it on my 
page...thanks, PB>>

Philip wrote:
> 
> 
> Cool...thanks for that...yeh I seem to remember
> something about the tants being a problem in that
> model.
> 
> Well I managed to fix a dead Quadra so I feel I could
> have a go at one of these..:)
> 
> Phil.
> 
> --- Malte Rogacki <gacki@... <mailto:gacki%40gacki.sax.de>> wrote:
> 
>  > At 17:08 Uhr +0100 08.05.2008, Philip wrote:
>  > > On the subject of arp stuff..Ive been thinking of
>  > > getting an Arp Omni but how come nearly every
>  > single
>  > > one I see is broken, not working, in need of
>  > repair
>  > > etc?
>  >
>  > There has been some discussion about this in the
>  > past few days. Some
>  > components inside the Omni are prone to failure.
>  >
>  > Here is a good description of the two typical
>  > problems:
>  >
>  > http://www.oldcrows.net/~oldcrow/synth/tips.txt 
> <http://www.oldcrows.net/~oldcrow/synth/tips.txt>
>  >
>  > The Omni uses quite a number of series 4000 CMOS
>  > chips; and also a huge
>  > number of tantalum caps. The one I'm currently
>  > trying to fix had a number
>  > of those chips and a number of those caps blown. The
>  > chips are very cheap;
>  > and I substituted electrolytic caps for the tantalum
>  > caps in the gating
>  > circuit. This got me about halfway to a working Omni
>  > - all voices produce
>  > sound now; and the gating circuits basically work
>  > (there are still some
>  > other problems, though).
>  >
>  > Anyway, it's a totally great sounding poly ensemble
>  > synth. The sound of
>  > those divide-down synths certainly is something
>  > special.
>  >
>  > The parts are cheap and mostly generic. I'm still
>  > learning all this stuff
>  > but I consider the Omni one of the easier to
>  > understand synths,
>  > circuit-wise. So if you want to learn to fix
>  > something a cheap non-working
>  > Omni might be a ticket.
>  >
>  > --
>  > Malte Rogacki gacki@... <mailto:gacki%40gacki.sax.de>
>  >
> ----------------------------------------------------------
>  > "Don't forget to TURN ON THE SYNTHESIZER. Often this
>  > is the reason why you
>  > get no sound out of it." (ARP 2600 Owner's Manual)
>  >
> ----------------------------------------------------------


-- 
Peter Brown
office: (413) 577-2747
cell: (413) 687-8287
AIM: pb0000math

On Thursday 08 May 2008 15:54, Malte Rogacki wrote:
> http://peterunderdog.com/arp/repair.html
>
> is another starting point.

I *strongly* disagree with a few statements that he makes there,  one of them 
being how tantalum capacitors degrade with age -- that's not the problem in 
the Omni,  running them too darn close to their rated voltage is,  and 
replacing them with 35V units (where the originals were 25V) takes care of 
that.  I also strongly disagree with his assertion that 4000-series CMOS 
parts degrade with age -- there's no basis for that at all,  as far as I can 
see.  He also doesn't impress me as being much of a technician if he smoked 
the power supply somehow (twice!) while troubleshooting some other problem...

> The beauty of the Omni is that large parts of it can be "debugged" one
> after another.
>
> Check power supply and power on boards.

Power supply should always be the first thing you check,  in anything you're 
working on -- if it's not right nothing else will be.

> Check master oscillator.
>
> Check divide-down circuitry.
>
> Check gating circuits.
>
> and so on.
>
> Repair-wise it's really a "one step at a time" synth; and that IMHO makes
> fixing it a bit easier than synths with a myriad on dependent functions.

Yup!

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

Great thanks a lot..I will do..

Phil.

--- Peter Brown <pbrown@...> wrote:

> hi Philip, i have Omni schematics & other info that
> might be useful for 
> you on the "ARP Omni Resource Page"
> 
> http://peterunderdog.com/arp/
> 
> i did a lot of work on my Omni but it still has
> issues that keep it from 
> sounding as good as the demo recording - can't get
> the String Controller 
> to work right, and half of the bass section (16'
> bass synth and string 
> section bass) doesn't work...the tants are a
> definite problem - i 
> replaced mine w/aluminum electrolytics, which i
> later found out is 
> probably not a good idea (i.e., should replace w/new
> tants)...however, 
> it sounds better now than it did w/the old tants and
> an old weird note 
> sustain problem that existed when i got the synth in
> "the 80s" (i.e., 
> 1980 :-) was apparently fixed in the process
> 
> if you find out any interesting info, let me know &
> i'll post it on my 
> page...thanks, PB>>
> 
> Philip wrote:
> > 
> > 
> > Cool...thanks for that...yeh I seem to remember
> > something about the tants being a problem in that
> > model.
> > 
> > Well I managed to fix a dead Quadra so I feel I
> could
> > have a go at one of these..:)
> > 
> > Phil.
> > 
> > --- Malte Rogacki <gacki@...
> <mailto:gacki%40gacki.sax.de>> wrote:
> > 
> >  > At 17:08 Uhr +0100 08.05.2008, Philip wrote:
> >  > > On the subject of arp stuff..Ive been
> thinking of
> >  > > getting an Arp Omni but how come nearly every
> >  > single
> >  > > one I see is broken, not working, in need of
> >  > repair
> >  > > etc?
> >  >
> >  > There has been some discussion about this in
> the
> >  > past few days. Some
> >  > components inside the Omni are prone to
> failure.
> >  >
> >  > Here is a good description of the two typical
> >  > problems:
> >  >
> >  > http://www.oldcrows.net/~oldcrow/synth/tips.txt
> 
> > <http://www.oldcrows.net/~oldcrow/synth/tips.txt>
> >  >
> >  > The Omni uses quite a number of series 4000
> CMOS
> >  > chips; and also a huge
> >  > number of tantalum caps. The one I'm currently
> >  > trying to fix had a number
> >  > of those chips and a number of those caps
> blown. The
> >  > chips are very cheap;
> >  > and I substituted electrolytic caps for the
> tantalum
> >  > caps in the gating
> >  > circuit. This got me about halfway to a working
> Omni
> >  > - all voices produce
> >  > sound now; and the gating circuits basically
> work
> >  > (there are still some
> >  > other problems, though).
> >  >
> >  > Anyway, it's a totally great sounding poly
> ensemble
> >  > synth. The sound of
> >  > those divide-down synths certainly is something
> >  > special.
> >  >
> >  > The parts are cheap and mostly generic. I'm
> still
> >  > learning all this stuff
> >  > but I consider the Omni one of the easier to
> >  > understand synths,
> >  > circuit-wise. So if you want to learn to fix
> >  > something a cheap non-working
> >  > Omni might be a ticket.
> >  >
> >  > --
> >  > Malte Rogacki gacki@...
> <mailto:gacki%40gacki.sax.de>
> >  >
> >
>
----------------------------------------------------------
> >  > "Don't forget to TURN ON THE SYNTHESIZER. Often
> this
> >  > is the reason why you
> >  > get no sound out of it." (ARP 2600 Owner's
> Manual)
> >  >
> >
>
----------------------------------------------------------
> 
> 
> -- 
> Peter Brown
> office: (413) 577-2747
> cell: (413) 687-8287
> AIM: pb0000math
> 
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

I forgot to say I got interested in the Omni after
hearing my Quadra..I'm guessing they sound similar? Or
am I way off? I thought it might be cheap alternative
to it. Quadra's seem to be worth quite a bit these
days...a bit more than I can hang on to if you know
what I mean. And I'm scared of it breaking down
again..the connection between the control panel
membrane buttons and the main board is one of the
worst, fragile..easy to rip and ruin forever, designs
I think I've ever seen.

I also have a RS-505 Paraphonic which I think is
similar to the omni...I do really love the 505 it is
one of the warmest, sweetest sounding string synths
I've ever used..It's become a real favourite since I
got it a while back.

Phil.



--- Malte Rogacki <gacki@...> wrote:

> At 17:08 Uhr +0100 08.05.2008, Philip wrote:
> > On the subject of arp stuff..Ive been thinking of
> > getting an Arp Omni but how come nearly every
> single
> > one I see is broken, not working, in need of
> repair
> > etc?
> 
> There has been some discussion about this in the
> past few days. Some
> components inside the Omni are prone to failure.
> 
> Here is a good description of the two typical
> problems:
> 
> http://www.oldcrows.net/~oldcrow/synth/tips.txt
> 
> The Omni uses quite a number of series 4000 CMOS
> chips; and also a huge
> number of tantalum caps. The one I'm currently
> trying to fix had a number
> of those chips and a number of those caps blown. The
> chips are very cheap;
> and I substituted electrolytic caps for the tantalum
> caps in the gating
> circuit. This got me about halfway to a working Omni
> - all voices produce
> sound now; and the gating circuits basically work
> (there are still some
> other problems, though).
> 
> Anyway, it's a totally great sounding poly ensemble
> synth. The sound of
> those divide-down synths certainly is something
> special.
> 
> The parts are cheap and mostly generic. I'm still
> learning all this stuff
> but I consider the Omni one of the easier to
> understand synths,
> circuit-wise. So if you want to learn to fix
> something a cheap non-working
> Omni might be a ticket.
> 
> -- 
> Malte Rogacki gacki@...
>
----------------------------------------------------------------------------
> "Don't forget to TURN ON THE SYNTHESIZER. Often this
> is the reason why you
>  get no sound out of it." (ARP 2600 Owner's Manual)
>
----------------------------------------------------------------------------
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

At 16:07 Uhr -0400 08.05.2008, Roy J. Tellason wrote:
> I *strongly* disagree with a few statements that he makes there, one of them
> being how tantalum capacitors degrade with age -- that's not the problem in
> the Omni, running them too darn close to their rated voltage is, and
> replacing them with 35V units (where the originals were 25V) takes care of
> that. I also strongly disagree with his assertion that 4000-series CMOS
> parts degrade with age -- there's no basis for that at all, as far as I can
> see. He also doesn't impress me as being much of a technician if he smoked
> the power supply somehow (twice!) while troubleshooting some other problem...

Given the number of smoked tantalum caps I've seen in various synths I'm
simply not sure if the caps produced about 30 years ago might not have a
more generic problem.

The german wikipedia states that older tantalum caps are sensitive to
low-ohm switching and could easily fail under such circumstances. Don't
know if this could be a reason.

As far as the 4000 series CMOS goes: I've already quoted another URL (also
found on Peter's site) with a description that I found pretty convincing:

http://www.oldcrows.net/~oldcrow/synth/tips.txt


In the last Omni I'm currently fixing about 5 of the 4000 series chips were
partly dead. Replacing them took care of all "dead" voices at once.

-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

On Thursday 08 May 2008 16:28, Malte Rogacki wrote:
> At 16:07 Uhr -0400 08.05.2008, Roy J. Tellason wrote:
> > I *strongly* disagree with a few statements that he makes there, one of
> > them being how tantalum capacitors degrade with age -- that's not the
> > problem in the Omni, running them too darn close to their rated voltage
> > is, and replacing them with 35V units (where the originals were 25V)
> > takes care of that. I also strongly disagree with his assertion that
> > 4000-series CMOS parts degrade with age -- there's no basis for that at
> > all, as far as I can see. He also doesn't impress me as being much of a
> > technician if he smoked the power supply somehow (twice!) while
> > troubleshooting some other problem...
>
> Given the number of smoked tantalum caps I've seen in various synths I'm
> simply not sure if the caps produced about 30 years ago might not have a
> more generic problem.
>
> The german wikipedia states that older tantalum caps are sensitive to
> low-ohm switching and could easily fail under such circumstances. Don't
> know if this could be a reason.

I don't know,  though I do see many references to them being a problem in 
older equipment,  Tektronix scopes being one of them.  Most of the time it's 
their sensitivity to overvoltage that's described as being the problem.

> As far as the 4000 series CMOS goes: I've already quoted another URL (also
> found on Peter's site) with a description that I found pretty convincing:
>
> http://www.oldcrows.net/~oldcrow/synth/tips.txt

I did look at that page as well and I'm not convinced,  though he at least 
gives me something to look for in terms of search terms.

> In the last Omni I'm currently fixing about 5 of the 4000 series chips were
> partly dead. Replacing them took care of all "dead" voices at once.

How did this manifest itself,  and what sorts of things were you observing in 
terms of the chips?

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

At 21:23 Uhr +0100 08.05.2008, Philip wrote:
> I forgot to say I got interested in the Omni after
> hearing my Quadra..I'm guessing they sound similar? Or
> am I way off? I thought it might be cheap alternative
> to it. Quadra's seem to be worth quite a bit these
> days...a bit more than I can hang on to if you know
> what I mean. And I'm scared of it breaking down
> again..the connection between the control panel
> membrane buttons and the main board is one of the
> worst, fragile..easy to rip and ruin forever, designs
> I think I've ever seen.

I don't exactly recall the panel connection (it probably has been over 10
years since I last looked at a Quadra). I only know the connection used for
the Chroma Polaris which is also very failure-prone.

Yes, Quadra's seem to fetch a really pretty amount nowadays. The Poly
section of the Omni is very similar to the one found in the Quadra. However
I *think* that phase shifter in the Quadra used a different design (I was
very impressed by that type of phasing). I seem to recall rumours that it
used some Mutron technology (ARP had bought Mutron at the time when the
Quadra was developed).
I'll have to check the schematics a bit more thoroughly about this.

> I also have a RS-505 Paraphonic which I think is
> similar to the omni...I do really love the 505 it is
> one of the warmest, sweetest sounding string synths
> I've ever used..It's become a real favourite since I
> got it a while back.

I think I had one of those for some time, too. My favourite string machine
is of course the Solina (I've got a Solina String Synthesizer, not the more
common String Ensemble). I've also got a Crumar Performer.
One string synth I'd love to hear would be the Freeman String Symphonizer.
I don't know if any of those ever found their way to Europe, though...


-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

On Thursday 08 May 2008 12:08, Philip wrote:
> On the subject of arp stuff..Ive been thinking of
> getting an Arp Omni but how come nearly every single
> one I see is broken, not working, in need of repair
> etc?
>
> Whats the story?

How much else that's out there in terms of electronics that's 30 years old do 
you know of that's still working well?  :-)

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

welllll....true..but I have to say Arp omni's appear
to particularly bad I've been watching ebay for
sometime...the last 4 or 5 on there have bee listed as
broken..

I have to say roland gear seems 'pretty' solid to
me...


--- "Roy J. Tellason" <rtellason@...> wrote:

> On Thursday 08 May 2008 12:08, Philip wrote:
> > On the subject of arp stuff..Ive been thinking of
> > getting an Arp Omni but how come nearly every
> single
> > one I see is broken, not working, in need of
> repair
> > etc?
> >
> > Whats the story?
> 
> How much else that's out there in terms of
> electronics that's 30 years old do 
> you know of that's still working well?  :-)
> 
> -- 
> Member of the toughest, meanest, deadliest, most
> unrelenting -- and
> ablest -- form of life in this section of space,  a
> critter that can
> be killed but can't be tamed.  --Robert A. Heinlein,
> "The Puppet Masters"
> -
> Information is more dangerous than cannon to a
> society ruled by lies. --James 
> M Dakin
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

The connectors are two thin membrane strips poking out
of a slot in the control panel metal work...very easy
to break, very awkward to unplug, plug in..and if you
did tear it or something, it's game over as you cant
get into the control panel.

Wow you have a Solina string synth...I've always
wanted to hear one of those. I have a very early
ensemble..it's been my favourite for years but I have
to say..the 505...it's catching up.



--- Malte Rogacki <gacki@...> wrote:

> At 21:23 Uhr +0100 08.05.2008, Philip wrote:
> > I forgot to say I got interested in the Omni after
> > hearing my Quadra..I'm guessing they sound
> similar? Or
> > am I way off? I thought it might be cheap
> alternative
> > to it. Quadra's seem to be worth quite a bit these
> > days...a bit more than I can hang on to if you
> know
> > what I mean. And I'm scared of it breaking down
> > again..the connection between the control panel
> > membrane buttons and the main board is one of the
> > worst, fragile..easy to rip and ruin forever,
> designs
> > I think I've ever seen.
> 
> I don't exactly recall the panel connection (it
> probably has been over 10
> years since I last looked at a Quadra). I only know
> the connection used for
> the Chroma Polaris which is also very failure-prone.
> 
> Yes, Quadra's seem to fetch a really pretty amount
> nowadays. The Poly
> section of the Omni is very similar to the one found
> in the Quadra. However
> I *think* that phase shifter in the Quadra used a
> different design (I was
> very impressed by that type of phasing). I seem to
> recall rumours that it
> used some Mutron technology (ARP had bought Mutron
> at the time when the
> Quadra was developed).
> I'll have to check the schematics a bit more
> thoroughly about this.
> 
> > I also have a RS-505 Paraphonic which I think is
> > similar to the omni...I do really love the 505 it
> is
> > one of the warmest, sweetest sounding string
> synths
> > I've ever used..It's become a real favourite since
> I
> > got it a while back.
> 
> I think I had one of those for some time, too. My
> favourite string machine
> is of course the Solina (I've got a Solina String
> Synthesizer, not the more
> common String Ensemble). I've also got a Crumar
> Performer.
> One string synth I'd love to hear would be the
> Freeman String Symphonizer.
> I don't know if any of those ever found their way to
> Europe, though...
> 
> 
> -- 
> Malte Rogacki gacki@...
>
----------------------------------------------------------------------------
> "Don't forget to TURN ON THE SYNTHESIZER. Often this
> is the reason why you
>  get no sound out of it." (ARP 2600 Owner's Manual)
>
----------------------------------------------------------------------------
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

At 16:40 Uhr -0400 08.05.2008, Roy J. Tellason wrote:

>> In the last Omni I'm currently fixing about 5 of the 4000 series chips were
>> partly dead. Replacing them took care of all "dead" voices at once.
>
> How did this manifest itself, and what sorts of things were you observing in
> terms of the chips?

Let's see:

one 4520: did not properly divide down on a single pin (all other pins worked)

one 4069: no output on some pins

three 4025: no output or intermittent output (here all pins of all three
chips were somehow affected while the two chips above worked at least
partly)

I also replaced a LM339 which appeared to be dead, too.


-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

On Thursday 08 May 2008 16:40, Malte Rogacki wrote:
> I think I had one of those for some time, too. My favourite string machine
> is of course the Solina (I've got a Solina String Synthesizer, not the more
> common String Ensemble). I've also got a Crumar Performer.
> One string synth I'd love to hear would be the Freeman String Symphonizer.
> I don't know if any of those ever found their way to Europe, though...

That had to have one of the more bizarre setups I've ever seen.  Right now I'm 
talking to a guy who wants that manual,  but we're still talking and have 
been for a while,  so it's still available,  as far as that goes.  (First one 
to make payment for it gets it :-).

It had a set of master oscillators _and_ top-octave synthesizer chips,  with 
separate sets of dividers,  and "animation" plus vibrato to liven things up a 
bit...

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

At 16:40 Uhr -0400 08.05.2008, Roy J. Tellason wrote:
>> The german wikipedia states that older tantalum caps are sensitive to
>> low-ohm switching and could easily fail under such circumstances. Don't
>> know if this could be a reason.
>
> I don't know, though I do see many references to them being a problem in
> older equipment, Tektronix scopes being one of them. Most of the time it's
> their sensitivity to overvoltage that's described as being the problem.

Well, the power supply decoupling caps in the various ARP synths are rated
35V and put across +15V and -15V to ground; and I've seen them fail
regularly (the current Omni being an example); I've also had this problem
with synths from other manufacturers and with effects boxes.


-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

At 16:59 Uhr -0400 08.05.2008, Roy J. Tellason wrote:
> That had to have one of the more bizarre setups I've ever seen. Right now I'm
> talking to a guy who wants that manual, but we're still talking and have
> been for a while, so it's still available, as far as that goes. (First one
> to make payment for it gets it :-).

How much?

-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

On Thursday 08 May 2008 17:06, Malte Rogacki wrote:
> At 16:59 Uhr -0400 08.05.2008, Roy J. Tellason wrote:
> > That had to have one of the more bizarre setups I've ever seen. Right now
> > I'm talking to a guy who wants that manual, but we're still talking and
> > have been for a while, so it's still available, as far as that goes.
> > (First one to make payment for it gets it :-).
>
> How much?

Taken offlist...

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

As I think I've said before the bulk of my electronics
experience is in fixing logic circuits, PSU's and
monitors in archaic arcade video games,like Space
Invaders and so on from the same sorts of periods as
synths..and I have to say where there's a tant there's
trouble, maybe 50% of the time.  


--- Malte Rogacki <gacki@...> wrote:

> At 16:40 Uhr -0400 08.05.2008, Roy J. Tellason
> wrote:
> >> The german wikipedia states that older tantalum
> caps are sensitive to
> >> low-ohm switching and could easily fail under
> such circumstances. Don't
> >> know if this could be a reason.
> >
> > I don't know, though I do see many references to
> them being a problem in
> > older equipment, Tektronix scopes being one of
> them. Most of the time it's
> > their sensitivity to overvoltage that's described
> as being the problem.
> 
> Well, the power supply decoupling caps in the
> various ARP synths are rated
> 35V and put across +15V and -15V to ground; and I've
> seen them fail
> regularly (the current Omni being an example); I've
> also had this problem
> with synths from other manufacturers and with
> effects boxes.
> 
> 
> -- 
> Malte Rogacki gacki@...
>
----------------------------------------------------------------------------
> "Don't forget to TURN ON THE SYNTHESIZER. Often this
> is the reason why you
>  get no sound out of it." (ARP 2600 Owner's Manual)
>
----------------------------------------------------------------------------
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

On Thursday 08 May 2008 17:20, Philip wrote:
> As I think I've said before the bulk of my electronics
> experience is in fixing logic circuits, PSU's and
> monitors in archaic arcade video games,like Space
> Invaders and so on from the same sorts of periods as
> synths..and I have to say where there's a tant there's
> trouble, maybe 50% of the time.

Do you figure that they're from a specific time period,  the ones that are 
going bad?

> --- Malte Rogacki <gacki@...> wrote:
> > At 16:40 Uhr -0400 08.05.2008, Roy J. Tellason
> > wrote:
> > > > The german wikipedia states that older tantalum
> > > > caps are sensitive to low-ohm switching and could easily fail under
> > > > such circumstances. Don't know if this could be a reason.
> > >
> > > I don't know, though I do see many references to
> > > them being a problem in older equipment, Tektronix scopes being one of
> > > them. Most of the time it's their sensitivity to overvoltage that's
> > > described as being the problem.
> >
> > Well, the power supply decoupling caps in the various ARP synths are rated
> > 35V and put across +15V and -15V to ground; and I've seen them fail
> > regularly (the current Omni being an example); I've also had this problem
> > with synths from other manufacturers and with effects boxes.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin

Hi Folks,

 This would be my first post. I thought I'd jump in now as you're discussing ARP Omnis.

My main thing is classic electro-mechanical gear, Hammonds, Wurlitzers, Rhodes, Clavinets, Mellotrons etc. My electronics knowledge isn't brilliant but I seem to get by and learn quickly.

 I do quite a lot of work on old synths too, I usually get there in the end but I'm having a bit of a nightmare with an Omni 2.

Everything now works beautifully but two of the switches don't behave as they should. These are in the left hand board, one controls the deep synth voice, the other the 'staccato' function for the bass. Essentially they switch on (once, after powering up) but won't switch off. The functions themselves are all fine, she sings. I just can't make these switches switch. Sometimes touching the legs of the associated transistor (not shorting them, I hasten to add!) with my scope probe triggers the switching.. All resistors appear fine.

 Any ideas? I'm impatient to get this finished and back to it's owner, especially as extensive work has made a dead dog of an Omni-2 into an otherwise lovely instrument.


Best wishes,

msw


________________________________
> To: vintagesynthrepair@yahoogroups.com
> From: rtellason@...
> Date: Thu, 8 May 2008 17:30:08 -0400
> Subject: Re: [vintagesynthrepair] arp omni
> 
> 
> On Thursday 08 May 2008 17:20, Philip wrote:
>> As I think I've said before the bulk of my electronics
>> experience is in fixing logic circuits, PSU's and
>> monitors in archaic arcade video games,like Space
>> Invaders and so on from the same sorts of periods as
>> synths..and I have to say where there's a tant there's
>> trouble, maybe 50% of the time.
> 
> Do you figure that they're from a specific time period, the ones that are
> going bad?
> 
>> --- Malte Rogacki 
_________________________________________________________________
Be a Hero and Win with Iron Man
http://clk.atdmt.com/UKM/go/msnnkmgl0010000009ukm/direct/01/

all this ARP Omni chatter has inspired me to scan & post the entire
service manual on my site:

http://peterunderdog.com/arp/omnimanual.pdf

PB>>

p.s., i love the smell of smoking power supplies in the morning...

--
Peter Brown
office: (413) 577-2747
cell: (413) 687-8287
AIM: pb0000math

On Thu, 8 May 2008, Mark Wallis wrote:

>
> Hi Folks,
>
> This would be my first post. I thought I'd jump in now as you're 
> discussing ARP Omnis.
>
> My main thing is classic electro-mechanical gear, Hammonds, Wurlitzers, 
> Rhodes, Clavinets, Mellotrons etc. My electronics knowledge isn't 
> brilliant but I seem to get by and learn quickly.
>
> I do quite a lot of work on old synths too, I usually get there in the 
> end but I'm having a bit of a nightmare with an Omni 2.
>
> Everything now works beautifully but two of the switches don't behave as 
> they should. These are in the left hand board, one controls the deep 
> synth voice, the other the 'staccato' function for the bass. Essentially 
> they switch on (once, after powering up) but won't switch off. The 
> functions themselves are all fine, she sings. I just can't make these 
> switches switch. Sometimes touching the legs of the associated 
> transistor (not shorting them, I hasten to add!) with my scope probe 
> triggers the switching.. All resistors appear fine.
>
> Any ideas? I'm impatient to get this finished and back to it's owner, 
> especially as extensive work has made a dead dog of an Omni-2 into an 
> otherwise lovely instrument.
>
>
> Best wishes,
>
> msw
>
>
> ________________________________
>> To: vintagesynthrepair@yahoogroups.com
>> From: rtellason@...
>> Date: Thu, 8 May 2008 17:30:08 -0400
>> Subject: Re: [vintagesynthrepair] arp omni
>>
>>
>> On Thursday 08 May 2008 17:20, Philip wrote:
>>> As I think I've said before the bulk of my electronics
>>> experience is in fixing logic circuits, PSU's and
>>> monitors in archaic arcade video games,like Space
>>> Invaders and so on from the same sorts of periods as
>>> synths..and I have to say where there's a tant there's
>>> trouble, maybe 50% of the time.
>>
>> Do you figure that they're from a specific time period, the ones that are
>> going bad?
>>
>>> --- Malte Rogacki
> _________________________________________________________________
> Be a Hero and Win with Iron Man
> http://clk.atdmt.com/UKM/go/msnnkmgl0010000009ukm/direct/01/

Differences for the phaser circuitry between ARP Omni and Quadra:

They are completely and totally different designs. The Quadra uses a
14-stage paheser built out of a transistor ladder. The Omni uses three
parallel delay lines.


-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

Hi again folks.

Does anybody have schematics for the ARP Omni-2? 

Best wishes,

msw
________________________________
> To: vintagesynthrepair@yahoogroups.com
> From: gacki@...
> Date: Fri, 9 May 2008 08:46:57 +0200
> Subject: Re: [vintagesynthrepair] arp omni
> 
> 
> Differences for the phaser circuitry between ARP Omni and Quadra:
> 
> They are completely and totally different designs. The Quadra uses a
> 14-stage paheser built out of a transistor ladder. The Omni uses three
> parallel delay lines.
> 
> --
> Malte Rogacki gacki@...
_________________________________________________________________

All new Live Search at Live.com

http://clk.atdmt.com/UKM/go/msnnkmgl0010000006ukm/direct/01/

What's "sdrawkcab" ?

At 6:05 Uhr -0700 09.05.2008, scott frye wrote:
> If the switches in question are capacitive touch you may want to replace the
> IC / transistor that gets that signal. I dont have a schematic so I'm only
> guessing.

The switches are momentary switches that drive a 4013. I guess this could
be the likely culprit here.


-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

If you do a google search for "ARP Omni-2" "service manual" you'll get a
number of hits for a PDF file.

The quality isn't the best, though.

-- 
Malte Rogacki gacki@...
----------------------------------------------------------------------------
"Don't forget to TURN ON THE SYNTHESIZER. Often this is the reason why you
 get no sound out of it." (ARP 2600 Owner's Manual)
----------------------------------------------------------------------------

Ok I switched on my Roland RS-09 tonight and it has a
definite problem now...I have C# playing all the time
fairly loudly in the background..It relates to C#1 on
the keyboard but its not a keyboard related problem if
you see what I mean. IE if i play the C# 1 key it
plays a louder C# on the top. It's across all the
sounds and is affected by the tune knob, transpose
etc. Any ideas before I break out the schematics?

Phil.


      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

Update: Its considered to be C#4 in the manual not 1..also just
looking at the schems it points towards a S10430 Chromatic Divider
IC...which is bad as that looks pretty hard to get. There are two
dividers and I think they may be in sockets so it'll be pretty fast to
just swap them round to test..


--- In vintagesynthrepair@yahoogroups.com, Philip <eggwheatis@...> wrote:

>
> Ok I switched on my Roland RS-09 tonight and it has a
> definite problem now...I have C# playing all the time
> fairly loudly in the background..It relates to C#1 on
> the keyboard but its not a keyboard related problem if
> you see what I mean. IE if i play the C# 1 key it
> plays a louder C# on the top. It's across all the
> sounds and is affected by the tune knob, transpose
> etc. Any ideas before I break out the schematics?
> 
> Phil.
> 
> 
>       __________________________________________________________
> Sent from Yahoo! Mail.
> A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html
>

Well looks like I've fixed it...just burning it in for a hour or two
now..it was a bad connection from IC201 which is one of the S10430
Divider IC's. Basically a bad solder joint, but it was absolutely
undetectable with the naked eye. I pushed the IC..the sound stopped, I
re-soldered the IC. Seems to be OK now.

Oh and the dividers are soldered in so no easy quick swap between the
two..they are 40 pin IC's. 

Also maybe this is a warning to those looking to buy an RS-09..RS-09's
are pretty cheap..but looking around the web for a spare S10430
divider IC showed that they are very hard to find and extremely
expensive. I found one IC for $150.

Phil.


--- In vintagesynthrepair@yahoogroups.com, "eggwheatis"
<eggwheatis@...> wrote:

>
> Update: Its considered to be C#4 in the manual not 1..also just
> looking at the schems it points towards a S10430 Chromatic Divider
> IC...which is bad as that looks pretty hard to get. There are two
> dividers and I think they may be in sockets so it'll be pretty fast to
> just swap them round to test..
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, Philip <eggwheatis@> wrote:
> >
> > Ok I switched on my Roland RS-09 tonight and it has a
> > definite problem now...I have C# playing all the time
> > fairly loudly in the background..It relates to C#1 on
> > the keyboard but its not a keyboard related problem if
> > you see what I mean. IE if i play the C# 1 key it
> > plays a louder C# on the top. It's across all the
> > sounds and is affected by the tune knob, transpose
> > etc. Any ideas before I break out the schematics?
> > 
> > Phil.
> > 
> > 
> >       __________________________________________________________
> > Sent from Yahoo! Mail.
> > A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html
> >
>

> Also maybe this is a warning to those looking to buy an RS-09..RS-09's
> are pretty cheap..but looking around the web for a spare S10430
> divider IC showed that they are very hard to find and extremely
> expensive. I found one IC for $150.

This sounds like the kind of thing that would be pretty easy to build out
of a PLD or FPGA on a board that has a 40-pin layout.  Cottage 
industry awaits.  Anyone have a PDF datasheet for the part?

Try: http://www.datasheetarchive.com/pdf/2948659.pdf



--- GB <grantbt@...> wrote:

> > Also maybe this is a warning to those looking to
> buy an RS-09..RS-09's
> > are pretty cheap..but looking around the web for a
> spare S10430
> > divider IC showed that they are very hard to find
> and extremely
> > expensive. I found one IC for $150.
> 
> This sounds like the kind of thing that would be
> pretty easy to build out
> of a PLD or FPGA on a board that has a 40-pin
> layout.  Cottage 
> industry awaits.  Anyone have a PDF datasheet for
> the part?
> 
> 
> 



      __________________________________________________________
Sent from Yahoo! Mail.
A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html