[sdiy] Jp-8 head scratcher

[The Laboratory of Sound]

On 2013-11-08 09:54, Maarten Halmans wrote:
> Hello,
> 
>> Maybe try deliberately detuning those oscillators by the opposite  
>> amount in calibration mode, and see what Compu-tune does then? Might  
>> be a workaround!
> 
> Nah, tried that. Oscillators are tuned again to the same/wrong
> frequency. Cheers,
> Maarten

So what happens if you calibrate the other voice cards to the wrong 
frequency of the misbehaving one? Will autotune overrule that as well?

Cheers,

Jack





> 
> 
>> Adam
>> On 07/11/2013, at 9:14 PM, Maarten Halmans wrote:
>> 
>>> Hello All.
>>> 
>>>> So you have *only* the KCV input driving the VCO pitch ?
>>>> Even after it leaves auto-tune ?
>>>> And it still has an error, even if you move the voice card to a  
>>>> different
>>>> location ?
>>> 
>>> Yes I disconnected all modulation sources and the problem still  
>>> persists! Moving the card moves the problem, so this rules out  
>>> wiring, module controller board, interface board and cpu board. I  
>>> moved the board serveral times because the problem I am having  
>>> points more to these boards than to the voice board. I also replaced  
>>> the tuning multiplexers, cv summing amp, transistor array.
>>> 
>>>> Could there be some kind of HF oscillation coming from somewhere  
>>>> that's
>>>> affecting the tuning ?
>>> 
>>> I looked with my scope at the cv summing amp, tuning output of the  
>>> oscillator but I don't see any oscillations nor on other places in  
>>> the tuning circuit (sample&holds multiplexers etc).
>>> When I look at the output of the comparator which goes to the  
>>> counter I see no difference between working and bad channels. I also  
>>> compared the output of the cv summing amp of the channels but the  
>>> slew rate is the same. I stop the repair for now because I keep  
>>> running in circles and keep testing the same things. But suggestions  
>>> are still more than welcome.
>>> 
>>> Best,
>>> Maarten
>>> 
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