Discussion about the Korg PolySix synthesizer

Welcome.   In manual mode, the voltage at each output of the two 4051's 18 and 19 should be adjustable
by changing the pot on the front panel that corresponds to it.   But that assumes the CPU is able to read 
the pot, which requires the signals that control the muxes on the panel to be connected and working,
and also the DAC and its comparator must be working.  Getting the DAC calibration working involves
much less code and hardware than normal operation, which is why I sometimes suggest it.  If you can't 
get that to work, then I would fix it before worrying about 18 and 19.   The scope is a really powerful
tool.   I would suggest that you use this as an opportunity to learn more about using it.  One technique 
that can work with digital circuitry is just probing lots of digital signals and looking for floats (trace eaten)
or intermediate voltage levels (could indicate a short).  You could also look at the DAC output and see if
it's trying to convert the front panel controls.   I uploaded some photos a while back that may help.

Bob

--------------------------------------------
On Wed, 8/17/16, Jim Wright tchgtrst@hotmail.com [PolySix] <PolySix@yahoogroups.com> wrote:

 Subject: [PolySix] Trying to Restore a P6.
 To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
 Date: Wednesday, August 17, 2016, 3:43 PM
 
 
  
 
 
 
   
 
 
     
       
       
       
 
 
 
 Hi,
    New member here who has been struggling for years to
 get a P6 working that was not stored well, and had the
 typical battery leakage.
 It's in good shape, without extensive damage to the
 KLM 367 board, but all of my attempts to get it working
 correctly have failed.
     Symptoms are:
 1. Does not power up properly with A and 1
 buttons lit.
  2.  It is possible to get sound from it, but adjusting
 any parameters from the MG, EG ,VCO, VCF, Effects or VGA
 sections causes random Bank, Programmer, Write, and Manual
 LEDs to light, which produces patches, noises, and
 sometimes nothing. I can find no
  pattern to this, except that D4 usually seems to produce a
 patch of some kind.
 3. The Arpeggiator and Key Assign modes seem to work just
 fine.
     
    I recently got the mod wheels, and tuning functions
 working again when I found problems with the traces
 associated with CN05 pin 12, and its connection to R10 and
 other components.
    Also pulled VRs 2, 3, 4, 5, 6, and 7, and found more
 corrosion under them, but fixing that did not seem to change
 it's behavior much. 
 PSU voltages check out fine and are adjustable.
   I have replaced IC 31, and checked all traces to it,
 as well as IC30 (though I did not replace IC30), and most
 other ICs on the board. All bad traces I can find were
 repaired.
 Battery was replaced with coin cell holder, as per the
 Old Crow site.
 Based on reading here, I have repeatedly checked all
 data, and "P" lines for continuity and have not
 found any problems or shorts.
 Everything connected to IC 22 has been checked several
 times compared to the schematic, and I have noted the errors
 found in the schematic, as listed on this group.
 I would also add that it appears that R83 should switch
 positions with VR6 on the schematic.
 Board has been cleaned and brushed with alcohol to remove
 any corrosion found.
 Multi-pin connectors to the other boards have been tested
 for continuity and found to be fine.
 
 
 
 My questions would be: 
      Can anybody recommend a good way to test ICs 18
 and 19? It seems most of the wrong-working controls are
 connected to these two ICs in some way. They seem to have
 proper power and ground connections. 
    Same goes for IC 30. Do the symptoms make it
 suspect? Should I replace it? 
    I've seen folks here recommend the D/A
 calibration for people with similar problems, but I
 can't get it to step 2 of the Reset adjustment, where
 Bank A and number 1 LEDs are lit.
    I'm happy to hear any suggestions of other tests
 to try, or places to look for a solution. Would love to get
 this working, and start using it. I DO have an oscilloscope,
 but am not well versed on it's use, though I am happy to
 learn.
 Thanks in advance for keeping this group going, and any
 responses.
 Jim
 
 
 
 
 Sent from Outlook
 
 
 
 
 
 
 
 
     
      
 
     
     
 
 
 
 #yiv0166812404 #yiv0166812404 --