Discussion about the Korg PolySix synthesizer

One thing to mention...   When you see a signal that looks wrong at the output of
a logic gate, the first thing to do is look at the inputs to that gate.   A floating or 
incorrect input can cause the output to be wrong.   Also, if the gate is being 
loaded down, that can affect its output.   To check for a load issue, with the synth 
powered off, measure from pin 4 to ground, and also from pin 5 to ground with a 
multimeter in the ohms position.   Keep the polarity of the leads the same for 
both measurements.  The readings should be similar, since both feed the INH inputs
of 4051 chips. 

IC23 contains four gates.   Of course, if one is bad, then the whole chip would be 
replaced.  Just saying that each of the four gates has two inputs and one output 
and they act independently.   
  
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On Wed, 8/24/16, 7zlwncpbis4x22jwvkd4oc5hzu2njcsjeup42is6@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:

 Subject: [PolySix] Re: Trying to Restore a P6.
 To: PolySix@yahoogroups.com
 Date: Wednesday, August 24, 2016, 4:10 AM
 
       
       I feel like I'm on to something
 here.The signal coming from pin 4, IC 23 is smeared
 on my scope, especially when it is compared to the pin 10
 signal. Not an inverse or any relation
 whatsoever.     Not only that, but I looked at
 the signals coming from the other side of IC 19, and I found
 that I could see the voltage change on all connections from
 IC 19 to such things as MG Level, MG Decay, KBD track, etc.
 The signal goes up about 70% on all of them, and then falls
 back to the lowest voltage. MG Freq, was the only one that
 didn't fall back to the lowest voltage. 
  When I looked at that side of IC 18....nothing on all
 parameters.   Did the corrosion get to IC 23?
 There are no external components in that part of the circuit
 to account for the smearing.Thanks for the
 pointers, Bob. I'm glad I got out my old analog scope,
 and am learning from it.