[sdiy] Jp-8 head scratcher

Jack Jackson jackdamery at hotmail.co.uk
Thu Nov 7 14:17:28 CET 2013


Slight thread hijack...Are the Jupiter 8 knob caps exactly the same part as the ones on the Juno 60?


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> From: diy at artefacts.nl
> To: synth-diy at dropmix.xs4all.nl
> Date: Thu, 7 Nov 2013 12:14:45 +0100
> Subject: Re: [sdiy] Jp-8 head scratcher
>
> 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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