Vintage Synth Repair

My MS-20 is acting up a bit, and I'm wondering if any of you have 
encountered and/or resolved similar problems to these.  The first is 
that if I turn the level control for VCO1 all the way down, and leave 
VCO2 level at maximum volume, I can affect the pitch of VCO2 with the 
scale control of VCO1.  This works the other way as well.  This seems to 
clear up after the synth has been powered on for some time (> 30 
minutes).  The other issue is that even with the cutoff frequency 
modulation level controls set to zero, the MG still has a small effect 
on the low-pass filter.  This symptom also seems to clear up similarly 
to the other problem, but not as consistently.

Hopefully these descriptions make sense.  If anyone has any suggestions 
or possible solutions, I would appreciate hearing them.

Thanks,

George

--- In vintagesynthrepair@yahoogroups.com, gnw <atonal@...> wrote:
>
> 
> My MS-20 is acting up a bit, and I'm wondering if any of you have 
> encountered and/or resolved similar problems to these.  






Sounds like a classic case of BCB contamination, where the problem varies with humidity/temperature. As it is pretty impossible for something to get poured into an MS-20 due to it's case design, perhaps a cap has leaked in there? Every MS-series synth I have had in for service lately has had bad electro's, they seem to be reaching their use-by date in those synths, and need replacing. My PS3100 was the same, every electo had leaked and started corroding the boards. In MS synths the leakage is much less, usually just some green on one of the legs of each cap.
>

Thanks for the suggestion; I was wondering about the possibility of it 
being cap-related.  I'll plan on opening it up this week and inspecting 
the boards.  I hear so many conflicting opinions regarding the 
replacement of electros; some say just go through and replace them as a 
preventive measure in older synths, while others seem to insist that the 
majority of these caps get replaced unnecessarily.  Obviously, if there 
is leakage evident as you've suggested, the replacement is warranted.

Thanks again!


thirteentech wrote:

> --- In vintagesynthrepair@yahoogroups.com, gnw <atonal@...> wrote:
>   
>> My MS-20 is acting up a bit, and I'm wondering if any of you have 
>> encountered and/or resolved similar problems to these.  
>>     
>
>
>
>
>
>
> Sounds like a classic case of BCB contamination, where the problem varies with humidity/temperature. As it is pretty impossible for something to get poured into an MS-20 due to it's case design, perhaps a cap has leaked in there? Every MS-series synth I have had in for service lately has had bad electro's, they seem to be reaching their use-by date in those synths, and need replacing. My PS3100 was the same, every electo had leaked and started corroding the boards. In MS synths the leakage is much less, usually just some green on one of the legs of each cap.
>   
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>
>

> Oops, my post should have read "PCB contamination" not BCB contamination. The issue of re-capping does come up a lot, and both answers are true - many caps get replaced unnecessarily, and many machines are also laboring under a load of bad electrolytics. 

Some reasons to replace electros in very old machines are:

Obvious leakage. 
Obvious lack of bottom end response.
If the machine has had periods of years where it has not been powered up. Electro's need voltage across them to keep them properly formed.
Situations where the model is known to be reaching the end of it's cap life, and as far as I have seen, Korg PS and MS series are definately there.
Caps that are being overheated, such as those mounted next to heatsinks and power resistors.

Reasons NOT to replace electro's:

If the caps are high quality, such as Spragues, and are in machines that have been kept in service. Outboard gear in large studios is a good example.  IN this case, removing a few caps and testing capacitance and ESR would be the obvious thing to do, and if they are still in spec, and the machine sounds good, then I would say leave it alone and re-test every 3 years.

The other option, is a "mini-re-cap" where you replace the caps in the audio path and VCF's only with high quality audio grade electrolytics such as Panasonics.

NOT the best advice dude.

Electrolytics capacitors have a very specific shelf life, whether charged regularly or otherwise. The chemicals breakdown over time regardless of use. Since most MS-20's are approaching 30 years of age or more, most of them have exceeded this time period, by about 5 years. Electrolytics do not only exist in the audio, but also play a role in control and timing of circuits, so lack of bottom end end is only one small symptom. Also a bad electrolytic may not show sign of leakage.

Furthermore, a mini recap in the audio chain only and VCF section, is the most intrusive choice sonically. It also wouldn't address the issues in this situation.

His problem sounds to me to be a cap related one, since there is a time factor in the problem. Sounds to me like the caps are becoming weak chemically are are taking longer to charge to full capacity.

Most vintage synths from the 70's and early 80's are at the end or way past their life in terms of electrolytics. Once you reach 25 years in age that's pretty much it, used often or never is irrelevant.

That's coming from an MSEE.

just my twocents

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

>
> 
> > Oops, my post should have read "PCB contamination" not BCB contamination. The issue of re-capping does come up a lot, and both answers are true - many caps get replaced unnecessarily, and many machines are also laboring under a load of bad electrolytics. 
> 
> Some reasons to replace electros in very old machines are:
> 
> Obvious leakage. 
> Obvious lack of bottom end response.
> If the machine has had periods of years where it has not been powered up. Electro's need voltage across them to keep them properly formed.
> Situations where the model is known to be reaching the end of it's cap life, and as far as I have seen, Korg PS and MS series are definately there.
> Caps that are being overheated, such as those mounted next to heatsinks and power resistors.
> 
> Reasons NOT to replace electro's:
> 
> If the caps are high quality, such as Spragues, and are in machines that have been kept in service. Outboard gear in large studios is a good example.  IN this case, removing a few caps and testing capacitance and ESR would be the obvious thing to do, and if they are still in spec, and the machine sounds good, then I would say leave it alone and re-test every 3 years.
> 
> The other option, is a "mini-re-cap" where you replace the caps in the audio path and VCF's only with high quality audio grade electrolytics such as Panasonics.
>

--- In vintagesynthrepair@yahoogroups.com, "John LeVasseur" <jrlaudio@...> wrote:
>
> NOT the best advice dude.
> 
> Electrolytics capacitors have a very specific shelf life, whether charged regularly or otherwise. The chemicals breakdown over time regardless of use. Since most MS-20's are approaching 30 years of age or more, most of them have exceeded this time period, by about 5 years. Electrolytics do not only exist in the audio, but also play a role in control and timing of circuits, so lack of bottom end end is only one small symptom. Also a bad electrolytic may not show sign of leakage.
> 
> Furthermore, a mini recap in the audio chain only and VCF section, is the most intrusive choice sonically. It also wouldn't address the issues in this situation.
> 
> His problem sounds to me to be a cap related one, since there is a time factor in the problem. Sounds to me like the caps are becoming weak chemically are are taking longer to charge to full capacity.
> 
> Most vintage synths from the 70's and early 80's are at the end or way past their life in terms of electrolytics. Once you reach 25 years in age that's pretty much it, used often or never is irrelevant.
> 
> That's coming from an MSEE.
> 
> just my twocents
> 

Did you actually read my post? Your advice sounds like it is coming from a classroom rather than from the real world.

> Did you actually read my post? Your advice sounds like it is coming from a classroom rather than from the real world.
>

Yes I did read your post. And with any machine over 25 years old there is NO REASON not to replace electrolytics, IN THE REAL WORLD. Even if the machine has been operating at relatively low temperatures (under 45 C) they are way past their life expectancy. Particularly in the case of Japanese electronics of this vintage. The capacitors used where not of the best quality from that era. That's the real world.

Also, Panasonics are not good capacitors by modern standards, when compared to manufacturers like Cornell-Dubilier or Nicon for instance. Panasonics actually have a relatively high variation in values and lower tolerances to temperature and life expectancy. That also is a real world assessment.

John is not kidding, some of these older synths did not make it even that
long with some of the lower
quality electrolytics. A good example, the Casio DH-100, while not something
you call a vintage synth, it
failed mainly due to the cheap off the wall electrolytic.

dale

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----- Original Message ----- 
From: "John LeVasseur" <jrlaudio@...>


>
> > Did you actually read my post? Your advice sounds like it is coming from
a classroom rather than from the real world.
> >
>
> Yes I did read your post. And with any machine over 25 years old there is
NO REASON not to replace electrolytics, IN THE REAL WORLD. Even if the
machine has been operating at relatively low temperatures (under 45 C) they
are way past their life expectancy. Particularly in the case of Japanese
electronics of this vintage. The capacitors used where not of the best
quality from that era. That's the real world.
>
> Also, Panasonics are not good capacitors by modern standards, when
compared to manufacturers like Cornell-Dubilier or Nicon for instance.
Panasonics actually have a relatively high variation in values and lower
tolerances to temperature and life expectancy. That also is a real world
assessment.

Im defintely of the 'if it aint broke dont touch it' school with caps. 

Yes of course electrolytics break down with age, but temperature and on-time have a huge role in accelerating that too.
 
I repair vintage arcade machine monitors for people. I re-cap every monitor as a matter of course. Many caps are shot in this situation. Re-capping fixes maybe 25% of faults and usually makes the picture look a bit better too. The monitors are subject to high temperature, high voltage, and very long on-time so it's not suprising.

I have to say in Roland synths I would never do such a thing. The rewards for doing so really are negligableas far as i'm concerned. They are on the whole still perfecly servicable...much more common to find bad sliders, pots, buttons..transistors, etc in this situation.

I Just troubleshooted a VP-330...bad SAD1024, SAD512, 2SC1815, BA662,..30 years old and the caps are still working fine..

But then take the Arp Omni and it's another story....the tants are terrible in that machine..as are the cmos IC for dying in that beast...

I just take it case by case using my experience(and others) as a guide, but I would never automatically cap everything just based on it being over 25 years old.

As a synth service tech for the last 28 years, I agree in principle that electros in old synths would be best replaced, and in some machines like Korg MS and PS series it is manadatory because they are all failing now. Minimoogs are the same, they always sound hugely better after a re-cap. As a tech I would love it if every customer that has an old piece of gear came in now wanting a re-cap, I could employ a couple of apprentices and make a fortune, but It would be untrue and unethical of me to start telling people that their old gear needs a lot of expensive work when the truth is that every day millions of people are making music with old un-recapped equipment.

Some machines respond better than others. I re-capped my Roland SH-7 a few months ago, the caps were actually starting to leak. I had another SH-7 in at the same time, and after replacing every electro in the synth is made absolutely no difference sonically in before and after comparisons with the other SH-7. Go figure. It needed to be done of course, the caps were leaking. 

But I also must say that I come across a lot of old outboard gear that has been constantly in service, and when I removed and tested the electros for capacitance and ESR, and they were all in spec. Yes, it would be nice to change them out anyway, but by real-world I mean that very few people have the money to have all of their old gear re-capped, and I don't think that it is really helpful to start people panicing by telling them that they must get every piece of vintage gear re-capped because all electros over 25 years old are completely degraded.


--- In vintagesynthrepair@yahoogroups.com, "John LeVasseur" <jrlaudio@...> wrote:

>
>  
> > Did you actually read my post? Your advice sounds like it is coming from a classroom rather than from the real world.
> >
> 
> Yes I did read your post. And with any machine over 25 years old there is NO REASON not to replace electrolytics, IN THE REAL WORLD. Even if the machine has been operating at relatively low temperatures (under 45 C) they are way past their life expectancy. Particularly in the case of Japanese electronics of this vintage. The capacitors used where not of the best quality from that era. That's the real world.
> 
> Also, Panasonics are not good capacitors by modern standards, when compared to manufacturers like Cornell-Dubilier or Nicon for instance. Panasonics actually have a relatively high variation in values and lower tolerances to temperature and life expectancy. That also is a real world assessment.
>

On Monday 13 April 2009 05:53:45 pm John LeVasseur wrote:
> NOT the best advice dude.
>
> Electrolytics capacitors have a very specific shelf life, whether charged
> regularly or otherwise. The chemicals breakdown over time regardless of
> use. Since most MS-20's are approaching 30 years of age or more, most of
> them have exceeded this time period, by about 5 years. Electrolytics do not
> only exist in the audio, but also play a role in control and timing of
> circuits, so lack of bottom end end is only one small symptom. Also a bad
> electrolytic may not show sign of leakage.
>
> Furthermore, a mini recap in the audio chain only and VCF section, is the
> most intrusive choice sonically. It also wouldn't address the issues in
> this situation.
>
> His problem sounds to me to be a cap related one, since there is a time
> factor in the problem. Sounds to me like the caps are becoming weak
> chemically are are taking longer to charge to full capacity.
>
> Most vintage synths from the 70's and early 80's are at the end or way past
> their life in terms of electrolytics. Once you reach 25 years in age that's
> pretty much it, used often or never is irrelevant.
>
> That's coming from an MSEE.
>
> just my twocents

Chemicals breakdown?  Can you point me toward any place that documents such 
stuff?  First I've ever heard of this,  and I'm pretty dubious about the 
whole recap thing to start with,  if it's not needed.

This coming from a tech for four decades or so...

> --- In vintagesynthrepair@yahoogroups.com, "thirteentech" <thirteentech@...> 
wrote:
> > > Oops, my post should have read "PCB contamination" not BCB
> > > contamination. The issue of re-capping does come up a lot, and both
> > > answers are true - many caps get replaced unnecessarily, and many
> > > machines are also laboring under a load of bad electrolytics.
> >
> > Some reasons to replace electros in very old machines are:
> >
> > Obvious leakage.
> > Obvious lack of bottom end response.
> > If the machine has had periods of years where it has not been powered up.
> > Electro's need voltage across them to keep them properly formed.
> > Situations where the model is known to be reaching the end of it's cap
> > life, and as far as I have seen, Korg PS and MS series are definately
> > there. Caps that are being overheated, such as those mounted next to
> > heatsinks and power resistors.
> >
> > Reasons NOT to replace electro's:
> >
> > If the caps are high quality, such as Spragues, and are in machines that
> > have been kept in service. Outboard gear in large studios is a good
> > example.  IN this case, removing a few caps and testing capacitance and
> > ESR would be the obvious thing to do, and if they are still in spec, and
> > the machine sounds good, then I would say leave it alone and re-test
> > every 3 years.
> >
> > The other option, is a "mini-re-cap" where you replace the caps in the
> > audio path and VCF's only with high quality audio grade electrolytics
> > such as Panasonics.
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>


-- 
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

> But then take the Arp Omni and it's another story....the tants are terrible
> in that machine..as are the cmos IC for dying in that beast...

Well,  yeah,  but they went and used a 25V part in a circuit where it could 
have 30V across the part,  a fact that came to my attention at the ARP 
factory in 1977.   :-)


-- 
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

Caveat:  I'm a total newb at this synth tech thing. ;) 

--- In vintagesynthrepair@yahoogroups.com, "thirteentech" <thirteentech@...> wrote:
*snip*

>  As a tech I would love it if every customer that has an old piece of gear came in now 
>wanting a re-cap, I could employ a couple of apprentices and make a fortune, but It 
>would be untrue and unethical of me to start telling people that their old gear needs a 
>lot of expensive work when the truth is that every day millions of people are making 
>music with old un-recapped equipment.

*snip*


>...Yes, it would be nice to change them out anyway, but by real-world I mean that very 
>few people have the money to have all of their old gear re-capped, and I don't think that 
>it is  really helpful to start people panicing by telling them that they must get every piece 
>of vintage gear re-capped because all electros over 25 years old are completely
>degraded.


It's always good to look out for one's customers and to approach business with an ethical mindset.  However, that also includes giving them accurate information about their synth.  Customers may want to spend the money for a recapping job, especially if it's a synth that's notorious for bad caps.  Give them the information and let them decide. 

As we mainly restore synths here, not repair them, recapping is standard procedure.   
I actually find it quite enjoyable work, especially with a cup of tea and a fully charged iPod.  And yes, having a power desoldering gun is a big part of it being an enjoyable job. ;)

~Monica

Quote:
> It's always good to look out for one's customers and to approach business with an ethical mindset.  However, that also includes giving them accurate information about their synth.  Customers may want to spend the money for a recapping job, especially if it's a synth that's notorious for bad caps.  Give them the information and let them decide. 
> 
> As we mainly restore synths here, not repair them, recapping is standard procedure.   
> I actually find it quite enjoyable work, especially with a cup of tea and a fully charged iPod.  And yes, having a power desoldering gun is a big part of it being an enjoyable job. ;)
> 
> ~Monica
>


Hi Monica, I absolutely agree with you, in any vintage restoration job a re-cap is mandatory. Therein lies the difference between restoration and repair. I do both, and I always give the customer the option to land anywhere along the scale from repair only to full restoration. Any synth that comes in that I feel would really benefit from a re-cap I let the customer know, and I often end up doing it. 

But the other side of the coin is far more common for a synth repairer, as an example: A kid brings in a scrappy OBXa with a couple of dead voices, bad key shims, bad pots and switches, the usual. The machine is a mess, he is nervous anyway as he doesn't have much money, and in the end I have to shave the cost down anyway because I finish up fixing the issues for which he brought the machine in, but I fix a half dozen smaller problems for free because I can't have a machine going out that isn't fully functional with my name attached to it.  Do you think I would bring up the subject of a re-cap in that circumstance? Absolutely not, he would never go ahead, and now he is going to go home and start worrying about capacitors. This is what I meant by "real world" in my earlier post.

It's fine for purists to jump up and down saying that every old machine must be re-capped when the come in for a repair, but they might as well say that every old car on the road should have and engine and tranny re-build next time it goes in for a service. It is a nice idea, but it is just not in not people's budget. 

I agree that customers should be informed about old electro's, but in a service centre you soon learn to know which customers it is a waste of time discussing the matter with, so I don't. I do a lot of re-caps every year, and I enjoy doing it, but I know when not to go there too.

Thanks to everyone who chimed in on this discussion!  I appreciate all 
the input very much.  I'll report my findings in a few weeks, once I get 
the MS-20 on the bench and have a look.

-George


thirteentech wrote:

>
> Hi Monica, I absolutely agree with you, in any vintage restoration job a re-cap is mandatory. Therein lies the difference between restoration and repair. I do both, and I always give the customer the option to land anywhere along the scale from repair only to full restoration. Any synth that comes in that I feel would really benefit from a re-cap I let the customer know, and I often end up doing it. 
>
> But the other side of the coin is far more common for a synth repairer, as an example: A kid brings in a scrappy OBXa with a couple of dead voices, bad key shims, bad pots and switches, the usual. The machine is a mess, he is nervous anyway as he doesn't have much money, and in the end I have to shave the cost down anyway because I finish up fixing the issues for which he brought the machine in, but I fix a half dozen smaller problems for free because I can't have a machine going out that isn't fully functional with my name attached to it.  Do you think I would bring up the subject of a re-cap in that circumstance? Absolutely not, he would never go ahead, and now he is going to go home and start worrying about capacitors. This is what I meant by "real world" in my earlier post.
>
> It's fine for purists to jump up and down saying that every old machine must be re-capped when the come in for a repair, but they might as well say that every old car on the road should have and engine and tranny re-build next time it goes in for a service. It is a nice idea, but it is just not in not people's budget. 
>
> I agree that customers should be informed about old electro's, but in a service centre you soon learn to know which customers it is a waste of time discussing the matter with, so I don't. I do a lot of re-caps every year, and I enjoy doing it, but I know when not to go there too.
>
>
>