Discussion about the Korg PolySix synthesizer

Hello there,


my  MK2 hat a broken joystick. I managed to fix it with an ancient fuse
holder made of a little tube and a bakkelit grip. (My grandpa got this
part from a telephone system somewhen back in the fifties.) Looks nice,
feels nice, works well.

But the external diameter of the joystick has increased. This means I do
net get the full octave any more when intensity is turned to 10 and I
pull the joystick intirely to the left or right. (The stick gets stopped
earlier due to the larger diameter.)

My idea was to adjust some trim pots somewhere to work around this
problem. But which of the many in the device are the right ones to start
tweaking?

BTW, I assume the tuning information that someone uploaded to the files
section of this group is still alright... the thing is a little detuned.

I gained some experience with the guts of the Trident and I'd like to
share them with others wo come along this wonderful device:

--snip---------------------------------------------------------------

PRECAUTION: Keep hands off the rightmost board and the big
transformer. High voltage. Electric hazard! Aaaaarg!
Everything at your own risk starting from opening the
lid anyways!

General advice for Trident (MK2) owners for repair:

- Clean potentiometers and switches with e.g. Kontakt 600 spray.
  Especially the volume knobs.
  These sprays are never perfect and some can do harms to
  potentiometers! Use them only if a potentiometer crackles.
  For the synthesizer section, use them if the knob doesn't
  change parameters continously but with jumps.
  For switches, it's relatively safe to use cleaning spreays.

- Replace the battery!
  The CPU will even crash if the battery is too low.

- Control the voltage of the battery directly after switching off
  and the next day.

- If voltage drops fast, check diode d3 in KLM-380, next to the
  battery. Replace if necesarry.

- If the battery has leaked heavily already, check carefully for
  damaged parts on KLM 380 and KLM 379. You might be in trouble.

Finding defective voices:

- turn on synthesizer section

- switch to key assign mode 2

- watch the LEDs on KLM-377; play in a way that they continously
  switch from one to the next. (fast re-trigger playing, but hold
  long, probably increase VCF release in the ENV section)

- the LEDs indicate which voice is used. Use your ears to find
  notes that don't sound as they should

-> No idea about electornics? Ask a professional and point
   him to the defective voice - will save you money.

-> Idea about electronics? Switch on oscilloscope!

- measure connectors 13--20 on LKM 378. This is the synthesizer board.

- on the leftmost wire, you should get a wave form that comes from
  KLM-379 (oszillator board). Switch VCO2 off and switch VCO1
  to simple sawtooth to get a clear picture.
  If you don't get a proper signal there, your KLM-379 may
  be in trouble.

- The rightmost wire seems to conduct trigger control voltage. If there
  there is no voltage when the corresponding LED turns on, you're
  having a problem somewhere between KLM-377 and KLM-378

- Still not found any hint? Erm. Most easy approach:
  Replace the SSM 2044 chip (this is the ADSR) with a neighbour
  voice that you know to work. Mark chips with little tape stripes
  to keep your overview.
  If you can "transplant" the error, you identified a defective chip.
  Do the same for the SSM 2056 (this one is for the VCFs).
  Use a special tang for this. The chips are expensive and you do
  not want to break the legs of a working one.

If you do not have a scope, you can count on your luck and just do
the last step...


--snap---------------------------------------------------------------

Enjoy the analog world!

Best,

   Niels



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