Discussion about the Korg PolySix synthesizer

First, infinite thanks to Jered, Andrew, and their team for all the terrific work in making these available!  I got mine on Thursday night and starting right in filling the vias, then installing the components.

I had ordered almost all the parts from Mouser and Digikey a few weeks ago so that they'd be ready when the PCB got here (another great thanks for the BOM that went along with the groupbuy!). 

It took me a total of about 6-8 hours to stuff the board - it was very helpful to have the old board right next to me to find component locations and double-check values.  Also, the old board provided a few key components that I couldn't easily track down.  Some unfun desoldering was involved, but all has gone pretty well so far.

I'm in the midst of recalibrating the new KLM367a in my Polysix.  The note I wanted to make was that I did just find an error in the PCB: 

R52 in the MG oscillator circuit (150 Ohm, 5%) was missing the trace tying it to ground.  It's an easy fix, as it's neighbor R51 (220 Ohm, 5%) also runs to ground, so you could make a jumper or a solder bridge.

More to come as I progress.  Again, I'm quite happy to be resurrecting this Polysix!!!

Hi,

Thanks for the Œheads up¹. I haven¹t actually seen the run of boards you
have because we are all covered in volcanic ash in the UK and hence no US
deliveries here in the UK! This is a weird one because R52 is a potential
divider feeding the inverting input  of the trans-conductance amp. Without
it I would imagine the oscillator would stall rendering the MG inoperative.
Not something we spotted during the R¹n¹D phase, plenty of others, but not
this one! Perhaps this is something that had crept in after the last wave of
mods. 

We¹ll be keeping a list of field issues and any subsequent run of boards
(would that be necessary?) will have the trace included.

Cheers,
Andy


On 18/04/2010 00:55, "kb_cheapmods" <kerrybradley@earthlink.net> wrote:

>  
>  
>  
>    
> 
> First, infinite thanks to Jered, Andrew, and their team for all the terrific
> work in making these available!  I got mine on Thursday night and starting
> right in filling the vias, then installing the components.
> 
> I had ordered almost all the parts from Mouser and Digikey a few weeks ago so
> that they'd be ready when the PCB got here (another great thanks for the BOM
> that went along with the groupbuy!).
> 
> It took me a total of about 6-8 hours to stuff the board - it was very helpful
> to have the old board right next to me to find component locations and
> double-check values.  Also, the old board provided a few key components that I
> couldn't easily track down.  Some unfun desoldering was involved, but all has
> gone pretty well so far.
> 
> I'm in the midst of recalibrating the new KLM367a in my Polysix.  The note I
> wanted to make was that I did just find an error in the PCB:
> 
> R52 in the MG oscillator circuit (150 Ohm, 5%) was missing the trace tying it
> to ground.  It's an easy fix, as it's neighbor R51 (220 Ohm, 5%) also runs to
> ground, so you could make a jumper or a solder bridge.
> 
> More to come as I progress.  Again, I'm quite happy to be resurrecting this
> Polysix!!!
> 
>  
>    
> 
> 



[Non-text portions of this message have been removed]

In looking into this further I discovered that once the MG section was working properly my own board I had LFO noise present on all the oscillators. 

This was a known problem with the original boards. The solution (which involves lifting one resistor leg, cutting one trace, and running one jumper wire) can be read about here: http://launch.groups.yahoo.com/group/PolySix/message/2125

I'm not sure if I should call this a new bug, an old bug, or just a KLM-367 bug!

Anyways, if others run into this problem you might try this solution.

I'm keeping my fingers crossed for no other errors.

Best,

Jed