Discussion about the Korg PolySix synthesizer

I looked at the KLM-366B board again. It has 6 holes. Holes 3 and 5 are not connected to any traces on the board. Hole 3 does have a pin from the P1501 connected to it, but the P1501 has no internal connection on pin 3.
 
The pin numbers on the VTL parts don’t match up with the pin numbers on the old P1501, but the resistor side of the VTL5C2 and VTL5C3 are pins 3,4 on the datasheet, not 1,2,3. They have two pins on the resistor, not three. The VTL5C3/2 has 5 pins and does have 3 pins on the resistor side numbered 3,4,5. Since pin 4 looks like a center tap on the resistor, and pin 5 on the KLM-366B is not connected to anything, you could safely put pins 3,4,5 into holes 4,5,6 on the board if you happened to have a VTL5C3/2 on hand and didn’t want to buy a VTL5C2 or VTL5C3.
 
Don B.



________________________________
From: Arp Duex <arpm234@yahoo.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com> 
Sent: Thursday, April 18, 2013 2:50 AM
Subject: Re: [PolySix] VTL5C2 opto coupler versus VTL5C3

  


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 <mailto:backshall1%40bellsouth.net>
To: mailto:PolySix%40yahoogroups.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: mailto:PolySix%40yahoogroups.com [mailto:mailto:PolySix%40yahoogroups.com] On Behalf Of
arpm234
Sent: Wednesday, April 17, 2013 2:39 PM
To: mailto:PolySix%40yahoogroups.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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