Discussion about the Korg PolySix synthesizer

Thanks for the awesome response... I just did a lot more soldering. So
far im not getting the random cutoff and the parameters seem good and
solid. Their is one remaining issue.

When I power it on, the presents work fine.  But in manual mode it
takes a minute for the cutoff to open.  what do i mean by this? i have
all the parameters set in a basic setting so i get a nice buzzing
sawtooth wave.  when I power it up when its been sitting for a while
and set it to manual, its like the filter cutoff is set to level 5, I
can barely hear it.  then after a minute (like it need to warm up)it
works fine.  now get this, before the warm up when the cutoff is not
working I can control the cutoff with the PW/PWM knob in the VCO
parameters. odd eh?
then after its warmed up I can shut it off and turn it back on and it
works fine.  its like a cap or a resister my be getting bad and it
needs to warm up.  I want to get some of that electronic cold blast
stuff to spray around to see if I can locate the suspected part.

Thanks everyone for reading... I hope other get use out of this post





--- In PolySix@yahoogroups.com, "synx508" <philyahoo@...> wrote:
>
> --- In PolySix@yahoogroups.com, "synthmdl76" <synthmdl76@> wrote:
> >
> > 
> > 
> > Sorry I meant board 367 not 376
> > 
> > Im checking the TP voltages righ now, then im testing the RESET.  If I
> > move VR1 when the cutoff is jumping that seems to effect the jumping
> > 
> 
> The fun thing about the battery leakage problem is that it can do many
> different things. The SIL pullup resistor near IC30/31 can go open
> circuit for certain lines, the lines can go open circuit to the
> microcontroller, they can go short (or effectively short for small
> signals) to other lines. The short problem is the hardest to track
> down and is also the reason that it's best to physically remove any
> tracks that appear to have been damaged. Once the corrosion has got
> into a track you can be sure it has also leaked under the protective
> coating on top of the board - this causes the PCB itself to become
> conductive!
> 
> If you have a 'scope you'll quickly be able to find a problem on one
> of the lines that feed in and out of IC30/31.
> 
> I don't think it can be emphasised enough that battery leakage is a
> tricky thing to fix if you're not already experienced in the many ways
> it can mess with your brain while you fault-find. It can be quite
> difficult to estimate the amount of repairs required, of the 3 I've
> done the cleanest looking was the one with the most damage. If I came
> across another unmodified polysix I'd remove IC30,31 and the
> microcontroller's socket and replace them all with sockets, cut and
> hard wire all the lines in and out of IC30,31 and perhaps the SIL
> resistor and maybe do the same for the CMOS stuff beside the battery
> before I even powered it on. ...or maybe I'd just rip its guts out and
> work on that Polytwelve project that I keep in a dark corner of my
> brain (which would be two 366s hanging off a modern microcontroller
> board).
>