Discussion about the Korg PolySix synthesizer

I found out that IC 1 pin 3 (the data pin) on the 370 board reads -2.3
and before it warms up.  that as it warms up and I can hear the cutoff
open, the voltage goes to -2.1 or so and stays stable.  
Maybe this ic1 14051 is bad.



--- In PolySix@yahoogroups.com, "synthmdl76" <synthmdl76@...> wrote:
>
> 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).
> >
>