Identify old capacitor?

Discussion in 'General Electronics Chat' started by CurlsOnKeys, Jan 4, 2015.

  1. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Hi all,

    opened up my old Rogue Moog synthesizer. I'm trying to identify all the "old" parts in it, but some are easier to find than others. All the elco's in my Moog are Matshusita, now known as Panasonic, really good quality elco's; ESR is perfect, even after 30 years.
    There are some TI IC's, two great tempco's (Tellab Q81's, not available anymore), but there's a brand of caps that I'm unable to find online. All the polyester/ceramic caps have "Mexico" printed on them, so I'm guessing that's where they were made, but I can't find the company. They all have a mysterious symbol, best described as a compass needle (or a double flag, or double arrow, or a diamond, or a double triangle, believe me, I googled all possibilities...).

    By accident I found a picture online of the exact same ceramic cap (I googled for "S3N", which seems to be the dielectric material), but there's no brand mentioned. You'll find it here: http://www.vetco.net/catalog/images/VUPN6742.jpg. The ceramic in the Moog is a 100 pF, 1000V (which seems extremely high by the way, any ideas why?) Maybe "S3N" can be a clue, since not a lot of caps seem to use this dielectric material (whatever "S3N" maybe, can't really find much info online about that either...). I found a company called Vishay who make caps with S3N as dielectric material, but they don't seem to use that compass needle symbol.
    The other cap in the Moog that also has Mexico and the strange symbol printed is a .01 uF 50V cap, with axial leads, that looks a bit like a small resistor or diode. No picture of that one (yet, I might upload one if extra clues are needed).

    So all you vintage electronic freaks 'n lovers out there, care to join me on this treasure hunt? :)
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Why are you so particular about who makes the capacitor?

    Once you can identify the capacitor's function and location in a circuit it would be easy to find modern replacements with proper type, value, tolerance and voltage.
     
  3. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Absolutely true. It's more out of curiosity on one side and also because I'd like to know if a certain type of cap has influence on the sound and if there were particular reasons to use that specific capacitor... For example, in the Moog, there's a .01 µF cap with the strange symbol and another totally different .01 µF cap with a much higher voltage rating (630, which to me seems totally unnecessary in a +12/-12V application), with another strange symbol (some kind of "9" reversed...). Why the difference? Also "S3N" seems a seldom used dielectric material. Is that pure coincidence? Or are there specific reasons?

    It puzzles me as to why one would pick a certain cap. I know, I know, it's not all that important and maybe they just picked a cap because they could buy it cheap, but maybe there are other reasons.
    Aside from that, I simply like the challenge to track down the parts in my old synth :)
     
  4. takao21203

    Distinguished Member

    Apr 28, 2012
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    sure each capacitor kinds gives a different sound.
    Ceramics have some microphonic effect and piezoelectric effect.
    At small voltages, and little vibration, its virtually not observeable.

    Also ceramics can change capacitance with voltage depends on the dielectric.

    Where's the schematic / board picture?

    For most circuits, you can almost use just any capacitor, resistor, transistor, change values and kinds, and the circcuit still does the same thing. You get a few parts maybe where you cant change the value so much.
    And a few critical circuits which are more noisy when you change the kind of component- particulary sensitive amplication circuits such as inside televisions or VCRs.

    In the end, as for audio, each circuit as a whole unit, will have its transmission spectrum, it will transmit/amplify some frequencies different than others. With an equalizer you can level it out and get that sterile noiseless studio sound- dynamic compressed, equalized, filtered and so on.

    Not sure if the moog relies on certain components to introduce some kinds of noise.
     
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  5. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Oh, but the Moog is not at all "sterile noiseless", so that's why I'm particularly interested in the "noise" or inequalities induced by certain components. There are lots of discussions about the impact of different capacitors on the sound (this one goes pretty deep http://forum.moogmusic.com/viewtopic.php?f=1&t=21944), so they certainly influence what comes out of a synth. Moog's famous ladder filter for example was constructed by cascading transistors. The transistors were simple 2N3904's, but the caps (playing a major roll in filtering) were maybe what defined the sound of the filter the most (as you can read in the above topic). Sure such a filter would work with new caps, but it would certainly sound different...

    You can find the schematic here (click to enlarge: http://www.cykong.com/Synths/Moog Rogue (Oakley)/Images/Moog Rogue Schematics Coloured.gif)

    I'm particularly interested in the caps used in the filter (C30, C31, C32, C33 in the "ladder" of transistors to the right of the schematic); they are the white boxes with some kind of underlined P-symbol as you can see here IMG_20150104_122216.jpg ) and also C17, C19, C20, used in the oscillator section in the middle; they are the ceramic disk cap and the axial cap, both labeled "Mexico", both with the compass needle symbol as you can see here (C17 IMG_20150104_122244.jpg and here C6 IMG_20150104_122315.jpg )

    Again: I'm convinced and perfectly agree that you can find new replacements for those old caps that will sound almost alike, but I'm still eager to find out what the old brands were they used. Sure some vintage electronic lovers must have come across some of these?
     
  6. bertus

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  7. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Well have you ever... I've been looking at this page for days now and never noticed the link! Thanks! Don't really fully get it though, S means 3.3 parts per million per °C, N means multiplier -1000 which gives -3300, which means that... for every drop of 1 °C, you get 3300 ppm less capacitance (+/- 2500 ppm tolerance as indicated by "N"). Which seems not particularly good?
     
  8. #12

    Expert

    Nov 30, 2010
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    Why, oh why, would a designer or builder choose such-and-such a part? Oh the anguish! Who can go back in time and read his/her mind for me??

    Here's a clue: About 40 or 50 years ago, there were so many 1000 pf caps rated at 1000 volts available on the surplus market that I still have about 40 of them. They aren't sonically pure, they're just cheap.
     
  9. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    They're sonically impure, that's what's nice about them :)

    Anyway, maybe this is the wrong place to ask this question. I'd seen some Moog fora with people arguing about certain caps and their sonic differences, struggling to identify some of them, so I thought I'd ask it on a dedicated electronics forum where maybe people would say "Hey, I recognize that cap; it's an old bladiebla from bladiebla". That's all. Nobody has to go back in time and ease my pain; I can perfectly live with it if nobody has ever seen these kinds of capacitors or if I'm the only one out here wondering what they are...

    I think I stated from the beginning I knew the main reason would probably be economics. Yet for example the caps in the Moog filter (the 27 nF, not the "1000 pF 1000V ones") are hand matched by 1%; people put a lot of time and effort in the design of those things, so I can't imagine they'd just pick the first and cheapest cap that landed on their desk... Hence the curiosity.
     
  10. #12

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    This isn't necessarily the wrong place, just I'm the wrong person to ask.
    I used to work with musicians in L.A. and I have been through this jungle of superstition so many times that I just can't stand it any more. Almost all engineers don't have a clue why an Orange Drop sounds different from any other brand of film capacitor. Only the Audiophiles know, and they all seem to know a different answer.

    You want Orange Drops in your Super Showman and green Chiclets in your TS-9? Fine. I can do that. What I can't do is explain the sonic characteristics of each brand.
     
    Last edited: Jan 4, 2015
  11. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Yeah, that tends to be a thing with Audiophiles (capital A). Relax, I'm not that kind of guy who tells you you should only record on tape, listen to vinyl and use a certain kind of wire gauge to connect your speakers :) I'm just interested in old synths, that's all. I'm trying to figure out which choices were made deliberately because of sonics or design and which choices were made because of economics.

    Let that be all for me motivating my question; back to answers! :)
     
  12. #12

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    Bringing it home now...Almost all engineers don't have a clue why one brand supposedly sounds different from another brand. This is mostly an engineers site. If I said XR brand electrolytics have a harsh, edgy sound, I would have to put this whole thread on my, "Ignore" list to keep my ego from being demolished by the uproar it would cause. You can have all the opinions you want, and you might get help identifying several particular brands and old markings, but you aren't likely to find anybody (here) saying, "why" somebody chose this or that brand 40 or 50 years ago.

    Personally, I read dozens of spec sheets about capacitors and found that metal film capacitors have the lowest dielectric energy absorption of all the capacitors I read about. That might be a reason some people like Orange Drops, but I don't know why any other brand of metal film cap is different.
     
    Last edited: Jan 4, 2015
  13. ian field

    Distinguished Member

    Oct 27, 2012
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    After capacitance value - tempco is probably the most important parameter to be aware of.

    Particularly with ceramic dielectrics, there's a wide variety of temperature coefficients.

    In this case "if it ain't broke - don't fix it" are wise words to follow.
     
  14. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Let me rephrase it one final time: I don't really expect anyone to say as to why somebody used a certain cap (unfortunately Bob is dead, so I can't e-mail him), but if people have certain insights in the cap used (being it the brand or other information), the rest is easy to deduct, no? If someone says: "I recognize the Mexican cap! They were very hard to get and you don't see them often in old gear", than I know it's probably an "expensive" piece, picked for certain reasons. The reason I posted this topic was for answers like Bertus gave or ian field here: if someone can tell me "S3N" is about temperature stability and someone else tells me that's a really important parameter, than I know: Ha, that cap was maybe picked for that particular reason! Knowledge leads to ehm more knowledge!

    ian, cool, thanks for the insights! "S3N" as temperature coefficient doesn't seem that great though or am I wrong? (S means 3.3 parts per million per °C, N means multiplier -1000 which gives -3300, which means that... for every drop of 1 °C, you get 3300 ppm less capacitance (+/- 2500 ppm tolerance as indicated by "N"). Which seems not particularly good?)
     
  15. takao21203

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    Apr 28, 2012
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    looking at the board pictures, my opinion is these parts are what was available back then, nothing special
    The circuit sections on the pictures dont look particulary finicky.

    High voltage ceramic capacitors are often blue these days if you inisist on that.

    the glass embedded parts are no longer made but inside there is kindof of an ordinary 1206 ceramic multilayer chip.

    The resistors are quite ordinary carbon film parts, the sliding pots arent high quality, look quite standard to me, just what was available back then.

    i guess if you change over the whole circuit to SMD it wont sound any different.
     
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  16. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
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    Cool, thanks. The glass and ceramic caps are least important, I particularly wonder what the white ones are, since they play an important role in the filter section. But nice to know about the 1206!
    Any thoughts on why they'd have used such high voltage ceramics? I don't really see a need, since all circuit voltages operate between +12 en -12, no?
     
  17. #12

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    That's the word that confuses me, but my opinion is: There were a butt load of high voltage, surplus ceramics on the market that decade. You could buy them by the pound.
     
  18. takao21203

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    boxed metal film capacitors, nothing special at all but sometimes sold at high prices online
     
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  19. CurlsOnKeys

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    Jan 3, 2015
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    So you study electronics, start reading schematics of devices that you really like, stumble upon strange symbols that you can't find, notice weird values that seem odd and you never ask yourself "why?" Ages ago, my math teacher started his first lesson with one word which he wrote on the blackboard: "curiousity!", upon which followed a lesson of great mathematical/scientific discoveries that were all made by people who were curious to know how certain things worked and started looking for answers. I like "why".
     
  20. MrChips

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    Oct 2, 2009
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    Why are certain types or characteristics of components selected over others?

    With the unit in question I would have to guess that it most cases the specific component was installed because that was what they had plentiful at hand.

    Take tolerance, for example. Someone may have installed resistors or capacitors with 1% tolerance in a filter or tone generator circuit. But does it make any sense to specify a resistor with 1% tolerance in series with a 10kΩ trim or control pot, for example?

    One may specify mica or polyester capacitors over ceramic, for example, for reliability or stability reasons but certainly not for audio qualities.

    The majority of long standing contributors here on AAC have strong science and engineering backgrounds and do not engage in audiophoolery or similar pseudoscience. We tend not to engage in discussing the virtues of tube amps vs solid-state amps, oxygen-free audio cables, or replacing capacitors for better sound.

    If those are the kinds of discussions and answers you seek then you have come to the wrong place.
     
    Last edited: Jan 4, 2015
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