Discussion about the Korg PolySix synthesizer

Hi!

You know I had the very same problem last week with a new board I was
building. I just couldn¹t get the calibration of the d/a converter right.
What had happened was I had selected the wrong resister for R84. It should
be 1K 1%. 1% resistors have a four band colour scheme where the fourth
denotes the number of zeros. I had mistaken it for a three band resistor and
soldered in a 10K 1%. So do be absolutely certain that R56, 57, 73, 74, 75,
83, 84, 85 and VR6/7 are the right values. Also check that you have soldered
the test switch in the right way and that you are in the default mode (see
Fig 1 service manual, section 8) and that the Œmanual¹ mode is selected.

Although I doubt it highly you might also want to substitute IC27 and let us
know which DAC chips you used for the clone board?

Cheers,
Andy


On 13/01/2011 01:01, "ML" <f115@rocketmail.com> wrote:

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> I had to set my 367 clone aside for some time and finally had a chance to get
> back to it. Sadly I can't get past that first step in the calibration. Patch
> LEDs 1-8 won't light up no matter what I do. I combed the earlier threads in
> the hopes of pinpointing the problem but so far it hasn't yielded results. One
> downside to my build here was that I originally set up headers that turned out
> to be problematic.
> 
> I followed the steps in an earlier thread:
> 
> - Check the continuity of the test mode switch
> - Make sure C28 is correctly positioned
> - Check resistive values around IC27
> - Carefully examine circuitry around IC33
> 
> I checked all resistor values. Some had some dips in resistance now that they
> were soldered onto the board but it didn't strike me as abnormal. Numerically
> they checked out so I carried on.
> 
> I checked all the caps and diodes against one of my original boards.
> 
> I've started to check all the voltages on the ICs. If a scope can show me the
> logic pulses you refer to on CN10 I should be able to hook something up but
> I'm pretty new to that. I only have a probe that connects to a sound card and
> I'm using an app called 'Scope' [go figure :)].
> 
> Any help would be greatly appreciated. Thanks!
> 
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