[sdiy] Original MS20 pitch tracking issue

[Tony K]

Hello, what exactly does "tracking in an uneven intervals" mean? I am not familiar with that converter, are you sure it is calibrated, i.e. exactly double the voltage for every octave? Measure it with a digital voltmeter , 41/2 digit if you have one. 

As others have pointed out , make sure you are using the Hz/V input , where normally the keyboard would be , VCO+VCO2 CV IN (Not the OCT/V or VCO1+2 Ext. Freq. control input , that one is the exponential input.) Always found this confusing myself. The schematic makes things clear what is what. VCO2 is also a linear input , or "Hz/V" . 

Inject voltages of 1.02, 2.05, 4.12 and 8.24 approximately into it and tune the synth according to the Korg service manual. (C1, C2, C3, C4)

Also the keyboard on the MS-20 provides a base voltage (transposition) and it might be something is screwy with that part of the circuit. 

Coincidentally we have been discussing all this Hz/V business , you might want to have a look at that.

Good Luck.






> On May 9, 2017, at 3:24 PM, Douglas Hock <hockd654 at newschool.edu> wrote:
> 
> Hi everyone,
> 
> I recently purchased an ms20 that was sawed in half to be rackmounted, but abandoned as a project. I installed it into the rack, powered and wired it up, and revived it.
> 
> Everything seems to work perfectly except for the pitch tracking on the oscillators. I'm sending HZ/V out of an Elektron Analog Keys (the racked ms20 has no keyboard) and it's tracking in uneven intervals. I have calibrated both oscillators with a tuner.
> 
> I was wondering if anybody here had some recommendations on where and what to look for. I figure some of you might have seen this issue.
> 
> Thanks!
> Doug
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