Vintage Synth Repair

I've narrowed my tuning problem to VCO-1 on Voice 1 in any
articulation mode (solo, unison, poly 1 and 2).  It won't respond to
the Computune command.  All other VCO's work great.  How does the
Computune feature work on the circuit level?  In other words, what
happens electrically when I press the TUNE button?  What could be
causing one VCO on one Voice to ignore the message?

Thanks for thinking it over with me.

Stephen


--- In vintagesynthrepair@yahoogroups.com, "easterleggs"
<milotoll@...> wrote:
>
> Hi, group.
> 
> I was fortunate enough to acquire a Roland Jupiter 8 w/Encore MIDI
> recently.  I've determined that it is the 12 bit version with variable
> split point.  (serial 120978)  Do the first two digits of the serial
> number refer to month (1 = January) and year (2= 1982)?  Assuming the
> numbering started at 0100 for the remaining four digits, would it be
> reasonable to assume mine is the 878th unit?
> 
> Also, what is the procedure for updating the D/A converter to 14 bit?
>  Is it as simple as replacing the 12 bit DAC or will it require more
> extensive modification?
> 
> Last, it is in need of calibration as there are some slight tuning and
> level variations among the voices.  Does the JP-8 have a 'voice
> defeat' feature so I can effectively mute the bad voices until I can
> calibrate it?  I saw no mention of it in the manual.
> 
> Any other information on this particular version or any tips and
> tricks would be appreciated!
> 
> Thanks,
> Stephen
>