[sdiy] Jp-8 head scratcher

[Adam Inglis]

Hi Maarten
Is the square wave of the affected oscillator at Test Point 1  
identical to the square wave the CPU reads from that board?
I'm thinking if the problem is on the voice board, then maybe the  
signal that goes back to the CPU is faulty? It must be pretty subtle  
though, the tuning difference is fairly minimal.

Adam
On 07/11/2013, at 1:48 AM, Maarten Halmans wrote:

> Hi all,
>
> I have some serious strange thing going on in a Roland Jupiter-8 and  
> I have no more clues where to look. I tuned all 16 voices and they  
> are very nice in tune over all octaves. They are well tuned on start  
> up (in test mode) and when the synth is on for several hours. So far  
> so good!
>
> The problem arrises when I use the auto tune. All voices stay tuned  
> except for 2 voices(on the same voice board). Oscillator 1 of both  
> voices is tuned to high. One voice is 12 cent off the other 6 cent.  
> Oscillator 2 of both voices is still in tune. So I swapped the voice  
> card to make shure it is not in de keyboard cv sample&holds or auto  
> tune multiplexers and the problems moves with the voice card. I also  
> disconnected all the modulation sources but all with no result.  
> Swapped the CV summing amp and the transistor array, which does not  
> make sense but you have to try something. I am completly in the dark  
> now. Sounds familiar to someone or does someone have suggestions or  
> ideas the find the problem? They are very welcome!!
>
> Best Maarten
>
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