Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

Hello all,

I just signed up today. I bought a Polysix off ebay which I arrived
here in Trondheim, Norway just before the holidays. It needs a fair
amount of work to be in 100% good condition and I've just been
checking the machine over to get an idea of what work it needs.

(I ought to introduce myself first: I'm Thomas, 31, living in
Trondheim, Norway. My main field of competence in electronics is
anything "obsolete", mainly stuff that's got tubes in it, but
anything analog is cool. I've built lots of amps, speakers etc. over
the years but have finally gotten around to exploring sound effects,
tone generators and synths as I'm getting back into performance
related music electronics. My main musical instrument is the flute,
but I find that synths are fun and useable even when I'm not much of
a keyboard player, for making "textures" and sonic "backdrops", sound
effects etc. I like progressive/psychedelic (and "space") rock,
mostly older stuff (Gentle Giant, Caravan, Camel, Yes, ELP, Gong
etc.) but am also a huge fan of Ozric Tentacles and some "neo" prog.
I previously own a Roland alphaJuno-1 and am in the process of
building a modular from RJ Wilsons designs.)

Yeah, anyway... I nervously unpacked the Polysix, described by the
seller as having "definitely seen better days", (certainly, from the
looks of it, knocked off corners on the wood parts, everything
covered with dust and grime...) Good thing all the keys and pot knobs
were undamaged. The plastic key covers are missing from three of the
memory select switches.

When I first powered it up, there was disappointingly little life in
it. Having read Old Crow's service instructions, I was anxious to
find out whether the battery had ever been replaced. Opened the thing
up and found that a lithium cell had been installed. I've ordered
a new SAFT 3.6V lithium battery just to be sure. At first glance
the circuit boards all looked surprisingly good apart from quantities
of dust. After brushing and blowing the worst dust out, sorting out
some intermittant connectors etc. the synth came to life. Still,
on closer inspection, it turned out that something I take to be
beer (rich, thick British variety) must have found its way into the
synth (through memory keypad area) and spread evenly over both the
KLM-367 and KLM-366. These both need a good cleaning. The KLM-366
seems only to have one of the VCOs off tune, otherwise works fine.

As I have no experience in washing&cleaning beer residue off PCBs,
I have asked around. Everybody seems to have their favorite
approaches. Soap/water, ultrasound, aerosol products etc. Most also
warn against washing a PCB that has trimmers/pots. I would like to
give the KLM-366 board as good a cleaning I can without risking
damage to the trimmers and/or having to retune all the oscillators.
I am hoping that most of the goo will come off with isopropanol (in
spraycans) and that I can protect the trimmers that way.

There is obviously something wrong with the KLM-367, in the
patch selector logic, and that PCB will probably get a good soak in
water w/ dish soap. There's a good layer of sticky goo covering
the top side of it. I mentioned the problem to Ingar
(iotech/analog.no), and he thought it most likely to be a problem
caused by insufficient cleanup after a past battery leak. There's
no sign of corrosion or damage to PCB trace, but there could be
some invisible residue from a battery leak still on, who knows.

I also have to come up with a safe and effective scheme for cleaning
all the control panel assemblies, with pots and everything. These are
quite dusty and I'd like to clean them as well. Or maybe I should
stick to the "if it ain't broke, don't fix it" wherever there's a
risk of messing up the pots? Any ideas?

Also, when preparing the KLM-367 for cleaning, I suppose I'll have
to remove the battery...? Will this erase the memory? Where can I get
the tapes with original patches?

I got the complete service manual the other day, but the synth is in
a workshop at a friend's place. I hope to get started on the cleanup
job within a few days.

Also, there's something not right with the octave and waveform
selectors and the VCF/VCO/VCA selector in the MG. With the schematics
in the manual I should be able to sort this out, or it could be
partly related to whatever is wrong with the KLM-367...?

I most urgently need to know what PC board cleaning schemes are
safe and effective since everything in the digital section will need
a good cleaning. Hope somebody can help!

Regards,

analogfuture/Thomas Dunker