Discussion about the Korg PolySix synthesizer

I brought home an oscilloscope last night.  It is indeed a square wave at Pin 7 of IC16.  Great!

In looking at its amplitude, I see that the amplitude of the square wave at the R53-R54 junction is the same as the amplitude of the triangle wave coming out of Q1.  So, if I want to use the square wave for my MG (LFO), I even know how to scale it! (come off Pin 7 of IC16 with a 47K/33K voltage divider)

So, now I have to figure out how to do the switching.  I need to be able to switch out the triangle wave and switch in the square wave.  And, it needs to be done in a way that doesn't mess up the timing of the MG oscillator, which means that I can't disconnect R26 from IC21 without reconnecting it to ground somewhere.  Should be straight forward enough, it'll just take some consideration.

Chip

--- In PolySix@yahoogroups.com, "chipaudette" <chipaudette@...> wrote:
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> Taking another look at the schematic (I don't have my oscilloscope right now, so I can't just go measure things to answer my own question), I think that I now see that Pin 7 (ie, the output) of IC16 might be a square wave.
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> Can anyone confirm (either through analysis or through measurement) that this is true?  At Pin 7, does it swing +/- 5V, or +/- 15V, or something else? ...I can't see where the power supply pins for IC16 are defined...
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> If this is a square wave at this location, I'd need to grab that signal, scale it with a voltage divider to get it the right amplitude for IC21, and then inject it into Pin 3 of IC21.  If I want a square wave MG, I'd inject this signal instead of the triangle wave coming down from R26.  That doesn't seem too hard to implement.  Cool.
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> The main trick is figuring out where to put a switch for this!
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> Chip
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>