[sdiy] Jupiter-6 Osc Sync?

[Tom Wiltshire]

Doug,

That looks tricky!

Looking around it, and looking at the CEM3340 diagram on another  
page, it looks like Cf is the 1000pF between pins 11 and 12 (C85A /  
C95A). I haven't looked much at the internals of the 3340 before, but  
it looks like a triangle core. Given that they're not using the on- 
chip sync pins, they must be either discharging the cap or switching  
the direction externally. Pin 11 is my bet for this, as this pin is  
connected to the ungrounded end of the cap, and also to the Roland  
custom chip that follows the osc. The sync reset is presumably done  
in there.

Good luck,
Tom



On 10 Feb 2010, at 07:29, Doug Terrebonne wrote:

> Hi, I've got a JP-6 here where on 1 voice VCO1<-VCO2 sync does not  
> work. Sync in the other direction on that voice does work. Can  
> anyone explain how the JP-6 does osc sync? It does not use the sync  
> onboard the CEM3340 (the pins are tied to ground) and all the  
> service manual says is "sync is accomplished by external  
> connections"... The service manual is here -
>
> http://manuals.fdiskc.com/flat/Roland%20Jupiter-6%20Service% 
> 20Manual.pdf
>
> The voice board schem is on page 16.
>
> Thanks for any help,
> Doug
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