Discussion about the Korg PolySix synthesizer

Hi and welcome to the list!

1) PWM:
IC13/pin1 should change in the range of -5V .. +5V with the front
panel "PWM SPEED" knob.
You should see on IC20/pin12 a sawtooth which changes the period
with the PWM SPEED setting. If it is not there, IC20, IC15, or C32
are defective; I would go for IC20 (a LM13600) first. But C32
could be a faster (and cheaper) try ..

2) ADSR:
Does the envelope work for the filter?
As with the PWM SPEED the first thing to check are the control
voltages output from the D/A converter - demultiplexers - hold
amplifiers: IC10/IC11/pin1/pin7. Each must swing from -5V to +5V.
Plus the EG mode switch: this is output at IC34/pin3. Switching the
front panel EG MODE switch back and forth should toggle the voltage
between 0 and +5V (ca). If not the culprit might be IC34 or on the
KLM-370 front panel or the cabling between KLM-377/KLM-370/KLM-366.

Be aware that other patch settings (such as Cutoff Freq, Resonance)
may cause the ADSR effect less audible. I suggest that you use a
setting with the filter all the way open and no resonance and the
EG setting at center position ("0").

I hope this helps,

Johannews

On 11.02.2014 20:11, victoranalo32@yahoo.es wrote:
>
>
> Hey guys, I found this site and I think fabulous,
> first thank any aid,
>
> I have a P6, I'm repairing but has 2 faults.
> First ruling in manual mode (ADSR) always sounds like gate, I think the
> switch does not work and does not reach the order,
>
> Second failure, I do not work the depth of pwm Speed.
> Greetings to all and thanks.
>
>
>
>
>

>
> Hello, I've been trying to find out about Speed ​​Pmw, now, in the output
> of operational ic 13, I see the change in line with the oscilloscope.
> Also at the base of Q2, D1 .. It seems that up here is good, do not you
> think?
>
> About the other problem, which does not work ADSR, is a problem in the EG
> switch, there are some presets that work with release, but other preset
> have no adsr, that does not work well for commutation, I looked, and belongs
> to do2 I've looked and I see a sign with my oscilloscope, and continuity
> with other ics ...
>

hello Johannews , 

Hi Victor,

The sawtooth will be more a triangle, sorry. And it is very slow, so you
should set the oscilloscope to DC.
Check the following (with oscilloscope or DVM):
- IC20/pin12: you say it follows the PWM SPEED potentiometer
- the same but ca 0.6V higher should be at IC20/pin7
- again the same but this time 0.6V lower (than pin12) at IC20/pin8
- check that IC15/pin6 is the same as IC20/pin8
- IC15/pin5 is constant, please tell the value (about 3V)
- IC15/pin7 is constant as well, probably about 13.5V
The circuit is fairly simple there should not go wrong much ...

Johannes

On 13.02.2014 18:26, zc40@hotmail.com wrote:
>
>
> hello Johannews ,
> thank you very much, I measured the level Ic13 pin 1, the probe, and
> have in dc -5 to +5. That seems fine.
> The IC 20 pin 12 output. I see nothing in ac, but putting the selector
> in DC, I see -01 to -5 v that I can modulate PWM Speed ​​potentiometer.
> I do not see the waveform you told me to AC, I changed IC20, c32, ic 15.
> But still does not work.
>
> Victor
>
>
>