Discussion about the Korg PolySix synthesizer

I've got a Polysix here that doesn't seem to initialize properly on cold mornings. Symptoms range from mild to bizarre. Sometimes I turn it on and the lights all come on, then it switches to just A,1,Poly like it should, but doesn't seem to have loaded all of patch A1 parameters properly. Hit the "1" button again and it's fine. Other times, none of the lights go off and hardly any knobs respond. If I leave it on for a few minutes, then turn it off and back on, it fires up properly. The Reset adjustment procedure was done after it was warmed up, as per instructions. Could it need tweaking for cold starts? How exactly does it work? With that big C21 and a zener, it looks like it just delays the initial reset until the 5v supply is up to snuff. 
Don B.

Hi Don,

Best thing to do measure pin 4 on the CPU at switch on.
The output from the comparator should drop active low for
about a second and then swing back to five volts. I had
a very similar problem a while back which looked like this.
One end was coming off the ceramic resonator! So do check the
REST pulse and draw you conclusions.

Cheers,
Andy




On 18 May 2010, at 14:14, "longenough2002" <backshall1@bellsouth.net>  
wrote:

> I've got a Polysix here that doesn't seem to initialize properly on  
> cold mornings. Symptoms range from mild to bizarre. Sometimes I turn  
> it on and the lights all come on, then it switches to just A,1,Poly  
> like it should, but doesn't seem to have loaded all of patch A1  
> parameters properly. Hit the "1" button again and it's fine. Other  
> times, none of the lights go off and hardly any knobs respond. If I  
> leave it on for a few minutes, then turn it off and back on, it  
> fires up properly. The Reset adjustment procedure was done after it  
> was warmed up, as per instructions. Could it need tweaking for cold  
> starts? How exactly does it work? With that big C21 and a zener, it  
> looks like it just delays the initial reset until the 5v supply is  
> up to snuff.
> Don B.
>
> 


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

I've removed them successfully several times to replace just tact switches. It's definitely ok if you're careful and you can even salvage the LED in the process.




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

Ermm. Whoops! Wrong thread :D




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

Well, the reset seems to be okay. That 6 MHz crystal on the other hand does not seem to be behaving well. I can't actually get a good picture of it on the oscilloscope. My probe has some obvious adverse effects on the signal, but is seems obvious that the frequency is increasing significantly as well as the amplitude over the first few minutes when the synth is on. The CPU is in big trouble until it gets a steady clock from the crystal. Should this be a sine wave? It looks like a sine now that it's warmed up. It was very spiky when cold. Not sure it any of this can be blamed on either of those two little capacitors. How safe is it to unsolder and resolder a crystal from another KLM-367?
Don B.

--- In PolySix@yahoogroups.com, Andrew Jury <andy@...> wrote:

>
> Hi Don,
> 
> Best thing to do measure pin 4 on the CPU at switch on.
> The output from the comparator should drop active low for
> about a second and then swing back to five volts. I had
> a very similar problem a while back which looked like this.
> One end was coming off the ceramic resonator! So do check the
> REST pulse and draw you conclusions.
> 
> Cheers,
> Andy
> 
> 
> 
> 
> On 18 May 2010, at 14:14, "longenough2002" <backshall1@...>  
> wrote:
> 
> > I've got a Polysix here that doesn't seem to initialize properly on  
> > cold mornings. Symptoms range from mild to bizarre. Sometimes I turn  
> > it on and the lights all come on, then it switches to just A,1,Poly  
> > like it should, but doesn't seem to have loaded all of patch A1  
> > parameters properly. Hit the "1" button again and it's fine. Other  
> > times, none of the lights go off and hardly any knobs respond. If I  
> > leave it on for a few minutes, then turn it off and back on, it  
> > fires up properly. The Reset adjustment procedure was done after it  
> > was warmed up, as per instructions. Could it need tweaking for cold  
> > starts? How exactly does it work? With that big C21 and a zener, it  
> > looks like it just delays the initial reset until the 5v supply is  
> > up to snuff.
> > Don B.
> >
> > 
> 
> 
> [Non-text portions of this message have been removed]
>

Hi Don,

I am actually away from the lab at the moment so can¹t give you an
absolutely definitive answer, but shouldn't a CPU clock be a square wave, or
there abouts? It certainly should be stable, even from a cold switch on. If
not then the patch banks and presets would go crackers until the P6 had
warmed up. It is perfectly possible to transplant the ceramic resonator from
one board to another, this I have done quite successfully in the past (it
only has two pins). However, do NOT make the same mistake as I did once and
use a 6Mhz clock crystal instead of a ceramic resonator. A crystal would
require extra circuitry. The Œ367 goes utterly bonkers with a crystal
fitted! Furthermore, ceramic resonators are available Œoff the shelf¹ from
most of the major component suppliers.

Hope this helps,
Andy

BTW. Let us know what you find. Your postings always make for good reading.


On 21/05/2010 17:16, "longenough2002" <backshall1@bellsouth.net> wrote:

>  
>  
>  
>    
> 
> Well, the reset seems to be okay. That 6 MHz crystal on the other hand does
> not seem to be behaving well. I can't actually get a good picture of it on the
> oscilloscope. My probe has some obvious adverse effects on the signal, but is
> seems obvious that the frequency is increasing significantly as well as the
> amplitude over the first few minutes when the synth is on. The CPU is in big
> trouble until it gets a steady clock from the crystal. Should this be a sine
> wave? It looks like a sine now that it's warmed up. It was very spiky when
> cold. Not sure it any of this can be blamed on either of those two little
> capacitors. How safe is it to unsolder and resolder a crystal from another
> KLM-367?
> Don B.
> 
> --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , Andrew
> Jury <andy@...> wrote:
>> >
>> > Hi Don,
>> > 
>> > Best thing to do measure pin 4 on the CPU at switch on.
>> > The output from the comparator should drop active low for
>> > about a second and then swing back to five volts. I had
>> > a very similar problem a while back which looked like this.
>> > One end was coming off the ceramic resonator! So do check the
>> > REST pulse and draw you conclusions.
>> > 
>> > Cheers,
>> > Andy
>> > 
>> > 
>> > 
>> > 
>> > On 18 May 2010, at 14:14, "longenough2002" <backshall1@...>
>> > wrote:
>> > 
>>> > > I've got a Polysix here that doesn't seem to initialize properly on
>>> > > cold mornings. Symptoms range from mild to bizarre. Sometimes I turn
>>> > > it on and the lights all come on, then it switches to just A,1,Poly
>>> > > like it should, but doesn't seem to have loaded all of patch A1
>>> > > parameters properly. Hit the "1" button again and it's fine. Other
>>> > > times, none of the lights go off and hardly any knobs respond. If I
>>> > > leave it on for a few minutes, then turn it off and back on, it
>>> > > fires up properly. The Reset adjustment procedure was done after it
>>> > > was warmed up, as per instructions. Could it need tweaking for cold
>>> > > starts? How exactly does it work? With that big C21 and a zener, it
>>> > > looks like it just delays the initial reset until the 5v supply is
>>> > > up to snuff.
>>> > > Don B.
>>> > >
>>> > > 
>> > 
>> > 
>> > [Non-text portions of this message have been removed]
>> >
> 
>  
>    
> 
> 



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

Both the crystal and capacitors have characteristics quite important to achieving god oscillation, especially in the old days. ;-)  Make sure all the values are spot on and that the crystal is of the correct type/cut. You should be able to use the crystal from the old board using normal desoldering techniques. Hope the old crystal is functional. Also be careful of too much flux or other contaminants in osc area.  

The scope will probably show a weak sine wave only. I don't have a Polysix, so I'm just speaking in general terms here. Where you should see a decent square wave is on the address lines (as low order as you can get without running into the data lines if they are multiplexed on this CPU).

GB

Thanks to Andy for clarifying the difference between the ceramic resonator and a crystal. If I had gone looking for a replacement, I would have purchased the wrong part for sure. I did move a resonator from another board to this one, and this board still has the problem. Sometimes it just flatlines for a few minutes after being turned on, then seems to resonate just fine. I replaced the 22pf and 10pf capacitors and now it resonates immediately but is fairly unstable. Actually, I didn't have a 22pf so I used a 20pf. So..... I ordered a bunch of tiny capacitors and now I guess it's also time to invest in a capacitance meter of some sort so I can see what I'm really sticking in there.

Don B.



--- In PolySix@yahoogroups.com, "grantpbt" <grantbt@...> wrote:

>
> Both the crystal and capacitors have characteristics quite important to achieving god oscillation, especially in the old days. ;-)  Make sure all the values are spot on and that the crystal is of the correct type/cut. You should be able to use the crystal from the old board using normal desoldering techniques. Hope the old crystal is functional. Also be careful of too much flux or other contaminants in osc area.  
> 
> The scope will probably show a weak sine wave only. I don't have a Polysix, so I'm just speaking in general terms here. Where you should see a decent square wave is on the address lines (as low order as you can get without running into the data lines if they are multiplexed on this CPU).
> 
> GB
>

Hi Don,

Of course the resonator is connected across pins 2 and 3 of the 8048. If you
have a spare it might be worth seeing if how it behaves with an alternative
connected. Also, if you still have the old blue 40 pin holder on this board
check very carefully that there is no hidden contamination beneath it. When
the wire link repairs were in vogue I would always replace the holder as a
matter of course. Just a thought...

Cheers,
Andy


On 28/05/2010 02:46, "longenough2002" <backshall1@bellsouth.net> wrote:

>  
>  
>  
>    
> 
> Thanks to Andy for clarifying the difference between the ceramic resonator and
> a crystal. If I had gone looking for a replacement, I would have purchased the
> wrong part for sure. I did move a resonator from another board to this one,
> and this board still has the problem. Sometimes it just flatlines for a few
> minutes after being turned on, then seems to resonate just fine. I replaced
> the 22pf and 10pf capacitors and now it resonates immediately but is fairly
> unstable. Actually, I didn't have a 22pf so I used a 20pf. So..... I ordered a
> bunch of tiny capacitors and now I guess it's also time to invest in a
> capacitance meter of some sort so I can see what I'm really sticking in there.
> 
> Don B.
> 
> --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , "grantpbt"
> <grantbt@...> wrote:
>> >
>> > Both the crystal and capacitors have characteristics quite important to
>> achieving god oscillation, especially in the old days. ;-)  Make sure all the
>> values are spot on and that the crystal is of the correct type/cut. You
>> should be able to use the crystal from the old board using normal desoldering
>> techniques. Hope the old crystal is functional. Also be careful of too much
>> flux or other contaminants in osc area.
>> > 
>> > The scope will probably show a weak sine wave only. I don't have a Polysix,
>> so I'm just speaking in general terms here. Where you should see a decent
>> square wave is on the address lines (as low order as you can get without
>> running into the data lines if they are multiplexed on this CPU).
>> > 
>> > GB
>> >
> 
>  
>    
> 
> 



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

Yes, the old blue 40-pin socket was still in there. Removed it, did a thorough cleaning, put in a new socket, and things are running much better. The resonator resonates with good stability and several of the signals from the CPU seem much cleaner. I've got another Polysix here with a similar problem so I'll have to find another 40-pin socket to try on that one. I finally got a capacitance meter but maybe I won't need it.

Don B.

--- In PolySix@yahoogroups.com, Andrew Jury <andy@...> wrote:

>
> Hi Don,
> 
> Of course the resonator is connected across pins 2 and 3 of the 8048. If you
> have a spare it might be worth seeing if how it behaves with an alternative
> connected. Also, if you still have the old blue 40 pin holder on this board
> check very carefully that there is no hidden contamination beneath it. When
> the wire link repairs were in vogue I would always replace the holder as a
> matter of course. Just a thought...
> 
> Cheers,
> Andy
> 
> 
> On 28/05/2010 02:46, "longenough2002" <backshall1@...> wrote:
> 
> >  
> >  
> >  
> >    
> > 
> > Thanks to Andy for clarifying the difference between the ceramic resonator and
> > a crystal. If I had gone looking for a replacement, I would have purchased the
> > wrong part for sure. I did move a resonator from another board to this one,
> > and this board still has the problem. Sometimes it just flatlines for a few
> > minutes after being turned on, then seems to resonate just fine. I replaced
> > the 22pf and 10pf capacitors and now it resonates immediately but is fairly
> > unstable. Actually, I didn't have a 22pf so I used a 20pf. So..... I ordered a
> > bunch of tiny capacitors and now I guess it's also time to invest in a
> > capacitance meter of some sort so I can see what I'm really sticking in there.
> > 
> > Don B.
> > 
> > --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , "grantpbt"
> > <grantbt@> wrote:
> >> >
> >> > Both the crystal and capacitors have characteristics quite important to
> >> achieving god oscillation, especially in the old days. ;-)  Make sure all the
> >> values are spot on and that the crystal is of the correct type/cut. You
> >> should be able to use the crystal from the old board using normal desoldering
> >> techniques. Hope the old crystal is functional. Also be careful of too much
> >> flux or other contaminants in osc area.
> >> > 
> >> > The scope will probably show a weak sine wave only. I don't have a Polysix,
> >> so I'm just speaking in general terms here. Where you should see a decent
> >> square wave is on the address lines (as low order as you can get without
> >> running into the data lines if they are multiplexed on this CPU).
> >> > 
> >> > GB
> >> >
> > 
> >  
> >    
> > 
> > 
> 
> 
> 
> [Non-text portions of this message have been removed]
>

Hi Don,

I am glad that worked out for you. As before it is an area of the Œ367 that
generally gets overlooked, but there is just enough space between those 40
legs for battery electrolyte to creep under and reek no end of havoc!

Cheers,
Andy


On 10/06/2010 03:57, "longenough2002" <backshall1@bellsouth.net> wrote:

>  
>  
>  
>    
> 
> Yes, the old blue 40-pin socket was still in there. Removed it, did a thorough
> cleaning, put in a new socket, and things are running much better. The
> resonator resonates with good stability and several of the signals from the
> CPU seem much cleaner. I've got another Polysix here with a similar problem so
> I'll have to find another 40-pin socket to try on that one. I finally got a
> capacitance meter but maybe I won't need it.
> 
> Don B.
> 
> --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com> , Andrew
> Jury <andy@...> wrote:
>> >
>> > Hi Don,
>> > 
>> > Of course the resonator is connected across pins 2 and 3 of the 8048. If >>
you
>> > have a spare it might be worth seeing if how it behaves with an alternative
>> > connected. Also, if you still have the old blue 40 pin holder on this board
>> > check very carefully that there is no hidden contamination beneath it. When
>> > the wire link repairs were in vogue I would always replace the holder as a
>> > matter of course. Just a thought...
>> > 
>> > Cheers,
>> > Andy
>> > 
>> > 
>> > On 28/05/2010 02:46, "longenough2002" <backshall1@...> wrote:
>> > 
>>> > >  
>>> > >  
>>> > >  
>>> > >    
>>> > > 
>>> > > Thanks to Andy for clarifying the difference between the ceramic
>>> resonator and
>>> > > a crystal. If I had gone looking for a replacement, I would have
>>> purchased the
>>> > > wrong part for sure. I did move a resonator from another board to this
>>> one,
>>> > > and this board still has the problem. Sometimes it just flatlines for a
few
>>> > > minutes after being turned on, then seems to resonate just fine. I
>>> replaced
>>> > > the 22pf and 10pf capacitors and now it resonates immediately but is
>>> fairly
>>> > > unstable. Actually, I didn't have a 22pf so I used a 20pf. So..... I
>>> ordered a
>>> > > bunch of tiny capacitors and now I guess it's also time to invest in a
>>> > > capacitance meter of some sort so I can see what I'm really sticking in
>>> there.
>>> > > 
>>> > > Don B.
>>> > > 
>>> > > --- In PolySix@yahoogroups.com <mailto:PolySix%40yahoogroups.com>
>>> <mailto:PolySix%40yahoogroups.com> , "grantpbt"
>>> > > <grantbt@> wrote:
>>>>> > >> >
>>>>> > >> > Both the crystal and capacitors have characteristics quite
>>>>> important to
>>>> > >> achieving god oscillation, especially in the old days. ;-)  Make sure
>>>> all the
>>>> > >> values are spot on and that the crystal is of the correct type/cut.
You
>>>> > >> should be able to use the crystal from the old board using normal
>>>> desoldering
>>>> > >> techniques. Hope the old crystal is functional. Also be careful of too
much
>>>> > >> flux or other contaminants in osc area.
>>>>> > >> > 
>>>>> > >> > The scope will probably show a weak sine wave only. I don't have a
>>>>> Polysix,
>>>> > >> so I'm just speaking in general terms here. Where you should see a
>>>> decent
>>>> > >> square wave is on the address lines (as low order as you can get
>>>> without
>>>> > >> running into the data lines if they are multiplexed on this CPU).
>>>>> > >> > 
>>>>> > >> > GB
>>>>> > >> >
>>> > > 
>>> > >  
>>> > >    
>>> > > 
>>> > > 
>> > 
>> > 
>> > 
>> > [Non-text portions of this message have been removed]
>> >
> 
>  
>    
> 
> 



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