Discussion about the Korg PolySix synthesizer

Quite tricky because I've looked at the board itself and pin 3 has a trace that goes somewhere. That contradicts the schematics which shows no pin 3 connected. 

5C3 has 3 pins and i had a look at the datasheet and the middle pin (pin 2) is connected to middle
of the photoresistance, something like a tapper in a potentiometer. 

pin 1 ----/\/\/[2]\/\/\/------ pin 3. 

If you look at the board all these pins are connected so wtf ?!?!?! :)

Razvan

________________________________
 From: backshall1 <backshall1@bellsouth.net>
To: PolySix@yahoogroups.com 
Sent: Thursday, April 18, 2013 4:40 AM
Subject: RE: [PolySix] VTL5C2 opto coupler versus VTL5C3
 


  
There are really only four pins used on the old optocoupler. If you number
them like a 6-pin DIP chip starting with the corner nearest R93 and move
counter-clockwise, then they would be:

1 - (+) Diode Anode, connected to ground

2 - (-) Diode Cathode, connected to R93

3 - Pin not connected to anything

4 - One side of photo-resistor

5 - No pin

6 - Other side of photo resistor

So, it's pin 3 that is not used on the diode side. I've used both VLT5C2 and
VTL5C3 as replacements, as well as the Silonex NSL32. On the last one I did,
I left the old R93 in and was able to tune it just fine. Usually I put in a
trimmer so I can see what R93 needs to be, but I got lucky that time. I know
it was a VTL part but I'm not sure if it was C2 or C3. Unfortunately, it
seems that these parts must be installed label-side down to get the diode
polarity right, so then you can't see the part number on it.

Don Backshall

_____ 

From: PolySix@yahoogroups.com [mailto:PolySix@yahoogroups.com] On Behalf Of
arpm234
Sent: Wednesday, April 17, 2013 2:39 PM
To: PolySix@yahoogroups.com
Subject: [PolySix] VTL5C2 opto coupler versus VTL5C3

Hello guys, 

I've just started to work on tunning the voices and i realised my opto
coupler is dead. 

So i read through the topics and learned that VTL5C3 would be the sollution.
However i only got VTL5C2 which has only two pin on the photoresistor side,
with a connection in the middle of the resistor which is connected to R93
which is said requires some changes. 

So what is that middle pin required for ? How can a 2 pin photocoupler be
used if possible at all ?

Any thoughts? 

Thanks
Razvan

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