Hi,
I wanted to let you know that I've finally managed to repair my
Precious (Polysix). It was indeed the opto resistor, the PC-1, that
was faulty. It was suggested to me that I replace the old mysterious
PC-1 component with a VTL5C3 and change R93 from 4k7 to 1k2 (to get
the VTL5C3 working properly). I did and then the synth was as good
as new!
Appearently, the PC-1 is what stabilizes the expo-converter circuit.
If it's broken, the circuit can't manage to keep the synth in tune
as the voltages vary (which is especially noticeable during the time
the machine is warming up).
Thanks for the help!
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/
> >>>>>>>
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> >>>>>>>
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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/
> >>>>>
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> >>>>>
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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:
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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:
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> >
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