Discussion about the Korg PolySix synthesizer

Alright, thanks! I'll get me some cooling spray, then get to work.

 Peter 

--- In PolySix@yahoogroups.com, Johannes Hausensteiner 
<jo.synth@c...> wrote:
> I would not start to replace all components; I would rather try
> to find out the faulty one. Heat up the whole area of the PCB
> using a hot fan. Then you can selectively cool down single
> components with cooling spray. If you start the Arpeggiator
> before you can let play the Polysix for its own and hear changes
> immediately.
> 
> Johannes
> 
> 
> Peter Andersson wrote:
> > 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
> >>>>>
> >>>>>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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> > 
> > 
> > 
> >