Discussion about the Korg PolySix synthesizer

You're right, searching for "2SC1583" does give me a bunch of 
interesting matches. No seller in Sweden but there are shops in 
Germany, for example, selling both that and the 2SA733. I'll ask a 
friend to get them and post them to me. Like you say, the opto 
resistor (PC-1) could be tough to get hold of, though. I'll start by 
replacing the transistors anyway and see if that does anything. Oh, 
and what about those amplifier ICs? Is that a long shot you think? 

Peter

--- In PolySix@yahoogroups.com, Johannes Hausensteiner 
<jo.synth@c...> wrote:
> I read from the schematic:
> * Q12 is a dual npn transistor, common emitter.
>    The used type is 2SC1583.
>    I found a company Dönberg Electronics, who does sell this
>    component, by entering "2sc1583" into Google
> 
> * Q3 is a standard (Japanese) pnp small signal transistor,
>    type 2SA733. Dönberg also do have this one or you can take
>    a BC557 as a substitute. But be careful, the pinout is
>    different:
>                   2SA733          BC557
>                    B-C-E          E-B-C
> 
> * PC-1 seems to be a Korg custom component. Doesnt it have a
>    black rubber tube on it? It is drawn in the schematics as
>    an LED optically coupled to an LDR. Hm.
>    Maybe someone of the list has a spare?
> 
> Johannes
> 
> 
> 
> Peter Andersson wrote:
> > Wow, that's very useful info! Thanks Johannes!
> > 
> > The control voltage must be crucial for the expo conversion to 
work 
> > properly then. If any of the amplifier circuits would be broken 
> > (IC17, 18 or 19), could that cause this behaviour do you think, 
or 
> > would that just make everything fail "from start"?
> > 
> > Well, speaking of which... The synth no longer tunes up 
correctly 
> > after 20 minutes. Now the tuning and the note intervals are 
screwed 
> > up period. So whatever needed "warming up" a few days ago seems 
to 
> > have failed permanently now.
> > 
> > I just went over the soldering points around the components you 
> > pointed out and resoldered most of them to be sure. I still get 
the 
> > same problem, though, so I guess it's time to start replacing 
> > components. I'll definitely try testing with cooling spray. Good 
> > suggestion! 
> > 
> > BTW, it seems I can replace all components in the expo 
conversion 
> > circuitry easily except Q12, Q3 and PC-1. Can't seem to find 
info on 
> > these anywhere. You wouldn't happen to know of components 
compatible 
> > to any of these three, would you?
> > 
> > Peter
> > 
> > 
> > --- In PolySix@yahoogroups.com, Johannes Hausensteiner 
> > <jo.synth@c...> wrote:
> > 
> >>The hold capacitors are C56 in unit0..5. But I do not think that 
it
> >>is the hold capacitors very likey. If it were, not all six voices
> >>would be affected equally. No, it must be something common. If it
> >>is not the wires to/from KLM-396, then the "expo converter" is my
> >>no.1 candidate. KLM-396 seems to be a part of it. The KBD works
> >>logarithmically; that is going up a certain number of keys (e.g.
> >>12 for one octave) multiplies the frequency of the generated note
> >>by a certain factor (times 2 in case of an octave). So the KBD CV
> >>logarithmic by its nature, whereas the oscillators work linear;
> >>that is, the generated frequency changes linearly with the 
control
> >>voltage (e.g 1V gives 1000Hz, 2V give 2000Hz, 3V give 3000Hz, 
> > 
> > etc.).
> > 
> >>These two schemes are not compatible to each other but it is 
> > 
> > possible
> > 
> >>(and necessary) to convert from one to the other. When converting
> >>from logarithmic to linear you have to do the opposite of 
logarithm
> >>which is exponential function. It happens that diodes and 
> > 
> > transistors
> > 
> >>have exponential transfer curves, so they can be used for this
> >>purpose. But the exponential function is extrem sensitive to 
small
> >>variations; a small variation of the input causes a big change at
> >>the output. Furthermore the human ear is very sensitive to 
changes
> >>in pitch. This means that there must be taken special measures 
that
> >>the whole thing does not run out of tune.
> >>The expo converter in the Polysix is made of IC17, 18, and 19, 
Q12
> >>(the expo component), PC-1 (kind of an opto-coupling device), Q3,
> >>and surrounding components. In case of "old production" units
> >>KLM-396 belong to this circuitry, too. Polysix has 6 voices but
> >>the analog (de)multiplexers for the CV have 8 inputs/outputs. The
> >>additional 2 inputs/outputs are used for some kind of calibrating
> >>the exp. amplifier and thus stabilizing tuning of the instrument.
> >>I am not 100% sure how this works as the CPU never measures any
> >>value and therefore cannot adjust to changing values. From what I
> >>can see from the code there is always the value 0 ouput 
to "voices"
> >>6 and 7.
> >>
> >>According to what you tell, it may be a thermal problem. So I 
would
> >>carefully check all solder points and try to heat up / cool down
> >>the PCB in the area where these components are located. With 
> > 
> > cooling
> > 
> >>spray you may identify a faulty component.
> >>
> >>Johannes
> >>
> >>
> >>Peter Andersson wrote:
> >>
> >>>Yes, it's an old production unit alright. I've checked the 
wires 
> >>>between the 366 and the 396. It seems ok, the solder joints too.
> >>>
> >>>Can you tell me which major components are actually involved in 
> > 
> > the 
> > 
> >>>lin/log conversion/tuning? I've been told to "check" the key 
> > 
> > voltage 
> > 
> >>>selector chip, the DAC and the S/H capacitors as well as 
> > 
> > something 
> > 
> >>>called an expo converter. (I don't understand half of this 
stuff 
> > 
> > to 
> > 
> >>>be honest - I know you're not surprised. I'm learning, 
though... 
> >>>quickly!). These are some of the key components of the 366 as 
> > 
> > far as 
> > 
> >>>I understand. Do they handle the conversion/tuning you're 
> > 
> > refering 
> > 
> >>>to? I thought I'd start out by replacing the S/H capacitors. 
The 
> >>>cheapest and easiest operation to start with, I thought. 
> > 
> > However, I 
> > 
> >>>haven't even been able to locate them. It's nearly impossibe to 
> > 
> > read 
> > 
> >>>the numbers on the 366 schematics I got off the Old Crow web 
> > 
> > site. 
> > 
> >>>(Man what a fantastic resource his site is, btw!).
> >>>
> >>>Again, thanks for helping!
> >>>
> >>>--- In PolySix@yahoogroups.com, Johannes Hausensteiner 
> >>><jo.synth@c...> wrote:
> >>>
> >>>
> >>>>From what you tell I would say it is a problem on the KLM-366, 
> > 
> > in
> > 
> >>>>the log/lin conversion/tuning section.
> >>>>Or maybe you have one of the rare "old production" units. Is 
> > 
> > there
> > 
> >>>>a small add-on board "KLM-396" to the KLM-366?
> >>>>It could be a lose wire (if "old production") and/or a bad 
solder
> >>>>joint.
> >>>>I can see that you are located in Sweden; maybe you ask Ricard
> >>>>( http://home.swipnet.se/ricard2/p6index.html ) for technical 
> > 
> > help.
> > 
> >>>>
> >>>>Peter Andersson wrote:
> >>>>
> >>>>
> >>>>
> >>>>>Actually, tones are quite stable even during the first 20 
> >>>
> >>>minutes, but
> >>>
> >>>
> >>>>>the synth is not in tune generally. Also, an octave is a 
quite 
> >>>
> >>>stable
> >>>
> >>>
> >>>>>major 7 interval for the first 20 minutes, until suddenly, 
the 
> >>>
> >>>synth
> >>>
> >>>
> >>>>>goes into tune and then the octave is correct as well. I'll 
> > 
> > check
> > 
> >>>>>tonight if a single generated tone changes a lot during the 
> >>>
> >>>first 10
> >>>
> >>>
> >>>>>sec.
> >>>>>
> >>>>>All six voices are affected. If I play a chord when it 
suddenly 
> >>>
> >>>slides
> >>>
> >>>
> >>>>>out of pitch, all notes follow. It actually sounds like I'm 
> >>>
> >>>turning
> >>>
> >>>
> >>>>>the pitch wheel. (I disconnected the pitch wheel, btw, just 
to 
> >>>
> >>>be sure
> >>>
> >>>
> >>>>>it wasn't playing tricks on me).
> >>>>>
> >>>>>It is not related to the MG setting and I've played around 
with 
> >>>
> >>>all
> >>>
> >>>
> >>>>>three - VCA, VCF and VCO. I'm quite sure it's not affected by 
> > 
> > the
> > 
> >>>>>waveform setting either (whether I use a saw or a pulse) but 
> > 
> > I'll
> > 
> >>>>>double check that tonight. The PWM setting does not make any
> >>>>>difference.
> >>>>>
> >>>>>Does this give you any clues? Thanks for helping!
> >>>>>
> >>>>>
> >>>>>--- In PolySix@yahoogroups.com, Johannes Hausensteiner 
> >>>
> >>><jo.synth@c...>
> >>>
> >>>>>wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>>>It is not normal that it takes 20 miuntes to tune up. 
Usually 
> > 
> > it
> > 
> >>>>>>takes about 10sec to tune and then it is quite stable.
> >>>>>>Check the following: hold a key down when switching power 
on. 
> > 
> > The
> > 
> >>>>>>generated note should change quite a lot until it stabilizes 
> >>>
> >>>after
> >>>
> >>>
> >>>>>>a few secs.
> >>>>>>Are all six voice affected? Is the effect related to the MG 
> >>>
> >>>setting
> >>>
> >>>
> >>>>>>(VCA/VCF/VCO)? Is it related to PWM setting?
> >>>>>>
> >>>>>>
> >>>>>>Peter Andersson wrote:
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>>Hi all,
> >>>>>>>
> >>>>>>>I'm the proud new owner of a Polysix. I love it! Can't take 
my
> >>>>>
> >>>>>hands 
> >>>>>
> >>>>>
> >>>>>
> >>>>>>>off those knobs - the filters are just great! But I'm 
having 
> > 
> > a 
> > 
> >>>>>>>problem with it and I'm hoping someone can tell me what it's
> >>>>>
> >>>>>about 
> >>>>>
> >>>>>
> >>>>>
> >>>>>>>and maybe even what can be done...
> >>>>>>>
> >>>>>>>After I've played the synth for a while, notes start to go 
> > 
> > out 
> > 
> >>>of 
> >>>
> >>>
> >>>>>>>pitch every now and then. It happens randomly every 10-30 
sec 
> > 
> > or
> > 
> >>>>>so. 
> >>>>>
> >>>>>
> >>>>>
> >>>>>>>The notes go off pitch with a note or so and always jump or 
> >>>
> >>>slide 
> >>>
> >>>
> >>>>>>>back to the original pitch again within half a second.
> >>>>>>>
> >>>>>>>At first I thought it was some filter setting of mine that 
> >>>
> >>>caused 
> >>>
> >>>
> >>>>>>>it, but as it turns out I get this no matter how the Poly6 
is 
> >>>>>>>programmed (or if I use a preset or a fresh "manual" 
sound). 
> > 
> > (By
> > 
> >>>>>the 
> >>>>>
> >>>>>
> >>>>>
> >>>>>>>way, it takes about 20 minutes for the unit to get in 
perfect
> >>>>>
> >>>>>tune 
> >>>>>
> >>>>>
> >>>>>
> >>>>>>>after a cold start. Don't know if that's normal or if it's
> >>>>>
> >>>>>related 
> >>>>>
> >>>>>
> >>>>>
> >>>>>>>to this problem in any way).
> >>>>>>>
> >>>>>>>I'd be truly grateful for any help!
> >>>>>>>
> >>>>>>>Peter
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6 
> >>>>>>>
> >>>>>>>
> >>>>>>>Yahoo! Groups Links
> >>>>>>>
> >>>>>>>To visit your group on the web, go to:
> >>>>>>>http://groups.yahoo.com/group/PolySix/
> >>>>>>>
> >>>>>>>To unsubscribe from this group, send an email to:
> >>>>>>>PolySix-unsubscribe@yahoogroups.com
> >>>>>>>
> >>>>>>>Your use of Yahoo! Groups is subject to:
> >>>>>>>http://docs.yahoo.com/info/terms/ 
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6 
> >>>>>
> >>>>>Yahoo! Groups Links
> >>>>>
> >>>>>To visit your group on the web, go to:
> >>>>>http://groups.yahoo.com/group/PolySix/
> >>>>>
> >>>>>To unsubscribe from this group, send an email to:
> >>>>>PolySix-unsubscribe@yahoogroups.com
> >>>>>
> >>>>>Your use of Yahoo! Groups is subject to:
> >>>>>http://docs.yahoo.com/info/terms/ 
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>
> >>>
> >>>
> >>>PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6 
> >>>
> >>>Yahoo! Groups Links
> >>>
> >>>To visit your group on the web, go to:
> >>> http://groups.yahoo.com/group/PolySix/
> >>>
> >>>To unsubscribe from this group, send an email to:
> >>> PolySix-unsubscribe@yahoogroups.com
> >>>
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> >>>
> >>>
> >>>
> >>>
> > 
> > 
> > 
> > PolySix "Digiest" Page: http://www.acc.umu.se/~amber/Poly6 
> > 
> > 
> > Yahoo! Groups Links
> > 
> > To visit your group on the web, go to:
> >  http://groups.yahoo.com/group/PolySix/
> > 
> > To unsubscribe from this group, send an email to:
> >  PolySix-unsubscribe@yahoogroups.com
> > 
> > Your use of Yahoo! Groups is subject to:
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> > 
> > 
> > 
> >