Discussion about the Korg PolySix synthesizer

Hi,

I bought an old Polysix that have been standing in a cellar for a longtime, and it was non working, and I suspected the leaking battery of course.

And that was one of the problem, the leaking battery.

So I replaced the battery and cleaned up everything and I repaired all the broken leads I could find on the circuit board.

And I have been checking every lead around the Processor and IC 30 and IC 31 and they all seems fine now.

And all the patchbanks works as they should now after my repair.

So now I get sound out from the Polysix and most of the functions seem to work as they should, but there is one big problem and that is the envelope generator controls.

When I turn the ADSR buttons it sounds like they controlling the filter instead of the envelope, they dont do any changes of the envelope at all.

So my question is: Can this malfunction still due to broken leads that I dont have found on KLM-367 or is it more likely that the problem is on another board now?

Peter

If you look at the schematic for the KLM-370 front panel pcb, you can see that the filter
controls and the ADSR controls are in the same 4051 analog mux.   The A,B and C select
inputs select one of the 8 analog values to be measured by the CPU board.   If the C line is stuck 
high, or possibly floating high, then the CPU will always select the D, S, and R pots along with the 
keytrack one.   It would select those pots even when it thinks it is measuring the filter cutoff and resonance
ones.   So maybe check that signal to see if it's connected all the way from the KLM-370 front panel board 
through the KLM-369 board, and back to the CPU board with a DMM in resistance mode.  
(synth powered down, of course)   If you have a scope, just check the signal at the 4051 mux on the KLM-370
to see that it is switching.

The chip could be bad.  Another thing you could try would be 
to (carefully) measure the DC voltage at these three pins with a DMM when the synth 
is powered.  You should see some voltage other than 0V or 5V, as the signals
should be changing and the meter will respond to the average.   Actually, 
if you use a DMM, the voltage values may jump all over the place due to the 
meter sampling, but at least that would tell you that the signals are changing 
at the chip, which is a little more definitive than measuring the resistance.

If it's easy for you to change the chip, then that would be something to try.
I can't say for sure that it's the problem.   Tough to diagnose things by email...

Good luck.

--------------------------------------------
On Tue, 5/2/17, peterovesterlund@gmail.com [PolySix] <PolySix@yahoogroups.com> wrote:

 Subject: Re: [PolySix] Envelope generator problem
 To: PolySix@yahoogroups.com
 Date: Tuesday, May 2, 2017, 8:30 AM
 
 
  
 
 
 
   
 
 
     
       
       
       Thank you for your answer Bob, I really appreciate
 it.And it sounds like the problem is somewhere in
 that area after your description about how A, B and C
 works.
 But today I
 measured both A, B and C line all the way from the MUX to
 the respective leg on the CPU, and it is full contact all
 the way.I dont have a scope so I cant check the
 MUX switching.Can it be the MUX itself that are
 broken maybe?
 I tried
 the control pots again and the Cutoff and the Decay makes
 almost exact the same changes in the filter.
 Peter
 
 
 
 
 
 
 
 
 
 
     
      
 
     
     
 
 
 
 #yiv7143848202 #yiv7143848202 --

The chip could be bad.  Another thing you could try would be
to (carefully) measure the DC voltage at these three pins with a DMM when the synth
is powered.  You should see some voltage other than 0V or 5V, as the signals
should be changing and the meter will respond to the average.  Actually,
if you use a DMM, the voltage values may jump all over the place due to the
meter sampling, but at least that would tell you that the signals are changing
at the chip, which is a little more definitive than measuring the resistance.

If it's easy for you to change the chip, then that would be something to try.
I can't say for sure that it's the problem.  Tough to diagnose things by email...

Good luck.



(re-sending.   I forgot to remove all of the junk that Yahoo's mail program 
inserts into my replies...)

One thing to keep in mind: it's not enough to check if the lines have
continuity; it's also important to check that they don't have contact to
another line.