[sdiy] seek help on Jupiter 6 repair

[jdm at synthcom.com]

At 11:53 AM 9/13/02 -0400, Anderson, Robert O wrote:
>The calibration procedure then says that the tune LED should
>extinguish after a few seconds..  Unfortunately it remains on. 

If there are ANY problems with the voice boards, the tune light will stay
on.  You could just as easily have a digital problem as an analog one.


>The volume and tune pots look damaged.  I would assume that the signal used
>in the tuning process comes before the volume pot.  Also, I assume that the
>tune pot is used in the tuning process.

No, the autotune is performed w/o the tune pot.  The tune pot is scanned by
the A/D and turned into a signed offset to the autotune value.


>  If these are the culprit I'll
>repair them at once, but I want to minimize removing the boards.

No need.  Good luck finding replacements, though.


>Does anyone have any experience with the Jupiter 6.  Is there any way to
>know where the tune is getting stuck, i.e. voice number.  

I guess I do - I reverse engineered and helped do a total rewrite of the
firmware on the controller board.  ;)  AFAIK, the only way to figure out
what is happening on the voice boards is to debug them the old fashioned
way.  One of the things on my to-do list is to add some diagnostic code to
the voice boards to help in debugging.  I've been getting more and more JP6
repair work, and could use the help.

JDM