[sdiy] The Korg MS-20 VCO core is oscillating!

[Mike Beauchamp]

Glad you got it working!

Someone told me that they proof read with the paper upside down. I've
never bothered trying it, but I wonder if tracing a breadboard
rotated 180 degrees would help to avoid "seeing" the expected.

Mike


On Sat, Apr 23, 2011 at 4:57 AM,  <lanterma at ece.gatech.edu> wrote:
> My students and I were able to get the MS-20 VCO core going on the breadbaord; thanks to the many people who offered advice.
>
> The problem, was, uhm, err... well... there's this diode, D4:
>
> http://www.korganalogue.net/korgms/images/service/ms20/circ1.gif
>
> It turns out it the circuit works much better if you have it the correct direction. ;)
>
> *Aaron hangs head in shame*
>
> I checked over their wiring around the CA3083 transistors multiple times, *including* looking at the diode, and somehow just never saw it until just recently, and I went "hey, is this diode going the right way?"
>
> It's like my brain interpolates what it expects to see and doesn't see what's there. I have that problem when proofreading all the time, especially if I'm proofreading something I just wrote; I have the same problem with equations I've just written on the board.
>
> (We're having trouble getting it to oscillate at low frequencies, but I think that's now just a matter of tweaking the current source.)
>
> - Aaron
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-- 
[mike]