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Restoring my Matrix-12

Restoring my Matrix-12

2010-07-11 by Joigaloid

Hello!  I have an Oberheim Matrix-12 that I would like to restore.  It spent a lot of time in storage (which caused a few problems) but there are a couple of functional problems I'd like to fix before attacking the cosmetic problems.  

The first issue is that I've noticed some notes were being dropped while playing.  After checking a few things with the tuning page I noted the following observations:

VCO Tuning:  Voice #6 fails
PW Tuning:  Voice #6 fails
Res & VCF Tuning:  Voices #6 and #12 fail
VCA Tuning:  Voice #6 fails

After tuning, the Matrix turns off the two failed voices.  I can always turn on voice #12 manually and get sound from it.  If I manually turn on voice #6, I get no sound from it.  All other voices are fine.

My guess on the above is that I've lost the Curtis VCO chip for voice #6.  The failure of voice #12 is more subtle, but it seems likely
I've lost the CEM3372 which performs all the filtering options.  I am faced with the frightening prospect of trying to locate a replacement 
CEM3374 and likely a CEM3372 as well.  

I will swap out chips between voices, but would prefer to keep swaps to a minimum.  The Matrix-12 has two identical voice boards, I'll have to guess which one is voices 1 through 6 and which one is voices 7 through 12.  Any suggestions?


I will be posting my experiences on this project both on the vintagesynthrepair and on the oberheim yahoo groups. Hopefully, others may benefit from them, and of course, I am open to any tips or suggestions from the group.

-as

Re: [vintagesynthrepair] Restoring my Matrix-12

2010-07-13 by Roger J

The last of the Oberheim Service dept. parts, including matrix are with John L, 
at 403-543-5127  






________________________________
Show quoted textHide quoted text
From: Joigaloid <andre_sand@...>
To: vintagesynthrepair@yahoogroups.com
Sent: Sun, July 11, 2010 7:21:18 AM
Subject: [vintagesynthrepair] Restoring my Matrix-12

  
Hello!  I have an Oberheim Matrix-12 that I would like to restore.  It spent a 
lot of time in storage (which caused a few problems) but there are a couple of 
functional problems I'd like to fix before attacking the cosmetic problems. 


The first issue is that I've noticed some notes were being dropped while 
playing.  After checking a few things with the tuning page I noted the following 
observations:

VCO Tuning:  Voice #6 fails
PW Tuning:  Voice #6 fails
Res & VCF Tuning:  Voices #6 and #12 fail
VCA Tuning:  Voice #6 fails

After tuning, the Matrix turns off the two failed voices.  I can always turn on 
voice #12 manually and get sound from it.  If I manually turn on voice #6, I get 
no sound from it.  All other voices are fine.

My guess on the above is that I've lost the Curtis VCO chip for voice #6.  The 
failure of voice #12 is more subtle, but it seems likely
I've lost the CEM3372 which performs all the filtering options.  I am faced with 
the frightening prospect of trying to locate a replacement 

CEM3374 and likely a CEM3372 as well. 

I will swap out chips between voices, but would prefer to keep swaps to a 
minimum.  The Matrix-12 has two identical voice boards, I'll have to guess which 
one is voices 1 through 6 and which one is voices 7 through 12.  Any 
suggestions?

I will be posting my experiences on this project both on the vintagesynthrepair 
and on the oberheim yahoo groups. Hopefully, others may benefit from them, and 
of course, I am open to any tips or suggestions from the group.

-as

Re: Restoring my Matrix-12

2010-08-14 by Joigaloid

After a few weeks, I claim Success!!  All twelve voices work and my Matrix-12 passes all tuning tests.

In the end, I needed to replace two Curtis Electromusic 3372 VCF chips.  Evidently, they can fail in different ways, since both my problem voices were due to 3372 failures.  My original theory that a dead voice was due to a 3374 VCO failure was dead wrong.

I was able to locate both the 3372 VCF and 3374 VCO chips from a European source.  Once they arrived, I discovered that my 3374 was fine after all, so I ended up with an extra CEM 3374 chip.  Given how scarce these are, I will keep it as a spare.  Replacing the two 3372s brought the two broken voices back to life and now all twelve of the  Matrix-12 voices are fully functional.

Lessons learned:  1.  I should have done more chip swapping in the beginning to isolate the fault.  2.  A bad 3372 can completely kill a voice.

Finally, to the engineers and designers at Oberheim:  I thank  you!  Thank you very much for including chip sockets in your board designs.  If I ever meet you in person, you are entitled to a few intoxicating (or not) drinks of your choice on me.

From the by-the-way department:  Upon searching for the Curtis Electromusic chips, I came upon some electronic parts vendors who would claim to have dozens in inventory.  These are electronics parts distributors that sell business-to-business, have minimum orders, etc etc. so I did not pursue them.  Just curious, but are they for real?  Has anyone obtained CEM chips this way?  Is it possible there are large numbers of these chips still in distributors warehouses?

PS:  Another btw:  The top voice board in the Matrix-12 is voices 7 through 12, the bottom board is voices 1 through 6

--- In vintagesynthrepair@yahoogroups.com, "Joigaloid" <andre_sand@...> wrote:
Show quoted textHide quoted text
>
> Hello!  I have an Oberheim Matrix-12 that I would like to restore.  It spent a lot of time in storage (which caused a few problems) but there are a couple of functional problems I'd like to fix before attacking the cosmetic problems.  
> 
> The first issue is that I've noticed some notes were being dropped while playing.  After checking a few things with the tuning page I noted the following observations:
> 
> VCO Tuning:  Voice #6 fails
> PW Tuning:  Voice #6 fails
> Res & VCF Tuning:  Voices #6 and #12 fail
> VCA Tuning:  Voice #6 fails
> 
> After tuning, the Matrix turns off the two failed voices.  I can always turn on voice #12 manually and get sound from it.  If I manually turn on voice #6, I get no sound from it.  All other voices are fine.
> 
> My guess on the above is that I've lost the Curtis VCO chip for voice #6.  The failure of voice #12 is more subtle, but it seems likely
> I've lost the CEM3372 which performs all the filtering options.  I am faced with the frightening prospect of trying to locate a replacement 
> CEM3374 and likely a CEM3372 as well.  
> 
> I will swap out chips between voices, but would prefer to keep swaps to a minimum.  The Matrix-12 has two identical voice boards, I'll have to guess which one is voices 1 through 6 and which one is voices 7 through 12.  Any suggestions?
> 
> 
> I will be posting my experiences on this project both on the vintagesynthrepair and on the oberheim yahoo groups. Hopefully, others may benefit from them, and of course, I am open to any tips or suggestions from the group.
> 
> -as
>

minimoog pitch center detent

2011-02-23 by Terje Winther

Hi all,
I have a minimoog in for minor service/calibration from a  
professional. Low serial number, and in very good shape.
The owner wants to have a larger center detent on the pitchbend wheel,  
and playing the mini I kind of agree: it is a bit hard to fint the  
exact center spot.
The center detent "click" is there, and careful playing in the studio  
is fine, but on the fly live I can imagine some strange off-tune  
unwanted sideeffects.
I think I remember seeing some mod to augment the center of the  
pitchwheel, but I can´t seem to find this. Anyone heard of this?
It is the standard, early thin white pitch and mod wheels with smooth  
surface.
Also, applying large amounts of pitchbend causes the VCOs to bend  
apart in pitch. I don´t think there is an individual calibration for  
this, so I will have to dig into the CV-summer and see what is wrong,  
I think.


Terje Winther
terje.winther@...
http://www.wintherstormer.no/

Re: minimoog pitch center detent

2011-02-23 by Quazimodo

I think that's done with two diodes in parallel, but opposite directions. Also you need to route a -10v feed to the wheel if I recall. Looks a simple mod, though I've never done it.

Cheers,
TOM



--- In vintagesynthrepair@yahoogroups.com, Terje Winther <terje.winther@...> wrote:
Show quoted textHide quoted text
>
> Hi all,
> I have a minimoog in for minor service/calibration from a  
> professional. Low serial number, and in very good shape.
> The owner wants to have a larger center detent on the pitchbend wheel,  
> and playing the mini I kind of agree: it is a bit hard to fint the  
> exact center spot.
> The center detent "click" is there, and careful playing in the studio  
> is fine, but on the fly live I can imagine some strange off-tune  
> unwanted sideeffects.
> I think I remember seeing some mod to augment the center of the  
> pitchwheel, but I can´t seem to find this. Anyone heard of this?
> It is the standard, early thin white pitch and mod wheels with smooth  
> surface.
> Also, applying large amounts of pitchbend causes the VCOs to bend  
> apart in pitch. I don´t think there is an individual calibration for  
> this, so I will have to dig into the CV-summer and see what is wrong,  
> I think.
> 
> 
> Terje Winther
> terje.winther@...
> http://www.wintherstormer.no/
>

Re: [vintagesynthrepair] minimoog pitch center detent

2011-02-23 by PeWe


Yes,- there´s a original MOOG "dead zone" mod for the pitch wheel center detend.
Have a look at the files section and leave a note if you don´t find it there.
Can be I have it somwhere on my machine too,- but that needs a search 1st.
Can´t promise, but I will have a look over the day.

In my Mini,- there´s different mod,- more like the one that works in a Prophet 5 and it works reliable since decades.
But that was done by a tech being out of biz since 2 decades or more.
I have his hand drawn sheets too somewhere, but I´m not sure it will be well readable for others and I have to find these too before I could do a scan.

PeWe

Am 23.02.2011 07:41, schrieb Terje Winther:
Show quoted textHide quoted text

Hi all,
I have a minimoog in for minor service/calibration from a
professional. Low serial number, and in very good shape.
The owner wants to have a larger center detent on the pitchbend wheel,
and playing the mini I kind of agree: it is a bit hard to fint the
exact center spot.
The center detent "click" is there, and careful playing in the studio
is fine, but on the fly live I can imagine some strange off-tune
unwanted sideeffects.
I think I remember seeing some mod to augment the center of the
pitchwheel, but I can´t seem to find this. Anyone heard of this?
It is the standard, early thin white pitch and mod wheels with smooth
surface.
Also, applying large amounts of pitchbend causes the VCOs to bend
apart in pitch. I don´t think there is an individual calibration for
this, so I will have to dig into the CV-summer and see what is wrong,
I think.

Terje Winther
terje.winther@...
http://www.wintherstormer.no/


[vintagesynthrepair] Re: minimoog pitch center detent

2011-02-23 by Malte Rogacki

I have the bulletin here (it's also in the files of the "The Lords of the
Mini" group). If it's not available elsewhere I'll upload it.

Another possibility could be this:

http://virtual-music.at/webseiten_d/zubehoer/moog_d.htm

(for some reason this isn't to be found on the English version of the site).

Re: minimoog pitch center detent

2011-02-23 by Doug

Hi,

The spring loaded teflon "wiper" thingy (can't think of a good term for it on only one cup of coffee) would wear and become a bit flat on the surface, thus not wanting to find it's notch in the detent as easily with use.

You can do one of a couple things.  
1) File the wiper teflon to a bit more of a point (not really the best approach)

2) Use a drill to enlarge the detent _SLIGHTLY_.  A little at a time becauwe a little goes a long way.

3) Replace the wheel with one of the newer moulded versions, though this would kill some of the early serial number's value.

The diode idea someone else suggested is also good, although I don't recall the modification right at the moment.  You'll need to do a fair bit of mods to the Mini to get this to work.

Hope that helps.

Doug

--- In vintagesynthrepair@yahoogroups.com, Terje Winther <terje.winther@...> wrote:
Show quoted textHide quoted text
>
> Hi all,
> I have a minimoog in for minor service/calibration from a  
> professional. Low serial number, and in very good shape.
> The owner wants to have a larger center detent on the pitchbend wheel,  
> and playing the mini I kind of agree: it is a bit hard to fint the  
> exact center spot.
> The center detent "click" is there, and careful playing in the studio  
> is fine, but on the fly live I can imagine some strange off-tune  
> unwanted sideeffects.
> I think I remember seeing some mod to augment the center of the  
> pitchwheel, but I can´t seem to find this. Anyone heard of this?
> It is the standard, early thin white pitch and mod wheels with smooth  
> surface.
> Also, applying large amounts of pitchbend causes the VCOs to bend  
> apart in pitch. I don´t think there is an individual calibration for  
> this, so I will have to dig into the CV-summer and see what is wrong,  
> I think.
> 
> 
> Terje Winther
> terje.winther@...
> http://www.wintherstormer.no/
>

Re: [vintagesynthrepair] Re: minimoog pitch center detent

2011-02-23 by PeWe

Yep, there it is,- not in the files section of vintage synth repair.
Forgot to mention,- sorry.


Am 23.02.2011 13:48, schrieb Malte Rogacki:
Show quoted textHide quoted text

I have the bulletin here (it's also in the files of the "The Lords of the
Mini" group). If it's not available elsewhere I'll upload it.

Another possibility could be this:

http://virtual-music.at/webseiten_d/zubehoer/moog_d.htm

(for some reason this isn't to be found on the English version of the site).



Re: [vintagesynthrepair] Re: minimoog pitch center detent

2011-02-23 by PeWe

Well,- these wiper thingys wear out soon.
I replaced mine by a replica made from nylon,- since then all is fine since decades.

Yes to 3.)

No to 2.) if the wheel is replaced

Terje,- where are you located ?
I have a new old stock moulded wheel and nylon wiper thingy as replacements and never used.
The nylon wipers are custom made and extremely reliable.


Am 23.02.2011 13:49, schrieb Doug:
Show quoted textHide quoted text

Hi,

The spring loaded teflon "wiper" thingy (can't think of a good term for it on only one cup of coffee) would wear and become a bit flat on the surface, thus not wanting to find it's notch in the detent as easily with use.

You can do one of a couple things.
1) File the wiper teflon to a bit more of a point (not really the best approach)

2) Use a drill to enlarge the detent _SLIGHTLY_. A little at a time becauwe a little goes a long way.

3) Replace the wheel with one of the newer moulded versions, though this would kill some of the early serial number's value.

The diode idea someone else suggested is also good, although I don't recall the modification right at the moment. You'll need to do a fair bit of mods to the Mini to get this to work.

Hope that helps.

Doug

--- In vintagesynthrepair@yahoogroups.com, Terje Winther wrote:
>
> Hi all,
> I have a minimoog in for minor service/calibration from a
> professional. Low serial number, and in very good shape.
> The owner wants to have a larger center detent on the pitchbend wheel,
> and playing the mini I kind of agree: it is a bit hard to fint the
> exact center spot.
> The center detent "click" is there, and careful playing in the studio
> is fine, but on the fly live I can imagine some strange off-tune
> unwanted sideeffects.
> I think I remember seeing some mod to augment the center of the
> pitchwheel, but I can´t seem to find this. Anyone heard of this?
> It is the standard, early thin white pitch and mod wheels with smooth
> surface.
> Also, applying large amounts of pitchbend causes the VCOs to bend
> apart in pitch. I don´t think there is an individual calibration for
> this, so I will have to dig into the CV-summer and see what is wrong,
> I think.
>
>
> Terje Winther
> terje.winther@...
> http://www.wintherstormer.no/
>


[vintagesynthrepair] Re: minimoog pitch center detent

2011-02-23 by Malte Rogacki

The deadband mod is now in the file section.

I did this on my MiniMoog (which has the newer type wheels). Before the mod
it would not reliably hit "zero" and just very miniscule moving of the
wheel resulted in clear out-of-tune-ness. After the mod the bending is rock
solid. Having to run an additional wire to the mod pot is a bit
inconvenient, but the results were exactly what I had hoped.

The deadband wiring was stock with a number of other synths - pre-PPC ARP
Odysseys (and probably other ARP's, too) and also later Moogs (at least the
Rogue).

Re: [vintagesynthrepair] Re: minimoog pitch center detent

2011-02-23 by Terje Winther

Excellent!
Thanks a lot.
Will do the mod and report back.

Terje Winther


Den 23. feb.. 2011 kl. 14.14 skrev Malte Rogacki:

The deadband mod is now in the file section.

I did this on my MiniMoog (which has the newer type wheels). Before the mod
it would not reliably hit "zero" and just very miniscule moving of the
wheel resulted in clear out-of-tune-ness. After the mod the bending is rock
solid. Having to run an additional wire to the mod pot is a bit
inconvenient, but the results were exactly what I had hoped.

The deadband wiring was stock with a number of other synths - pre-PPC ARP
Odysseys (and probably other ARP's, too) and also later Moogs (at least the
Rogue).



Re: minimoog pitch center detent

2011-03-01 by Quazimodo

Silicone grease!


--- In vintagesynthrepair@yahoogroups.com, PeWe <ha-pewe@...> wrote:
Show quoted textHide quoted text
>
> Well,- these wiper thingys wear out soon.
>

Re: minimoog pitch center detent

2011-03-02 by Doug

Capital idea Sir.  Available in the "plumbing" ailse!

--- In vintagesynthrepair@yahoogroups.com, "Quazimodo" <noddyspuncture@...> wrote:
Show quoted textHide quoted text
>
> Silicone grease!
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, PeWe <ha-pewe@> wrote:
> >
> > Well,- these wiper thingys wear out soon.
> >
>

Re: [vintagesynthrepair] Re: minimoog pitch center detent

2011-03-22 by Terje Winther

Hi all,
Thanks a lot for the responses regarding the center detent for the minimoog.

I think that's done with two diodes in parallel, but opposite directions. Also you need to route a -10v feed to the wheel if I recall. Looks a simple mod, though I've never done it.

I finally did the mod. Had to wait for my parts supplier to find the right precision resistors (332k - fairly odd). Quite easy to do the mod.
It did make the center detent a notion wider, Not much, rather subtle change, actually, but probably enough for a performer to notice.
The mod is also said to improve on VCO stability, and I did actually notice that. Probably subtle that too, being an early minimoog with the early VCO card so it is probably drifting a little anyway.
I am happy with the mod, and I hope my client is too.
Thanks a lot for all the feedback on this.



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