Discussion about the Korg PolySix synthesizer

yeap. you are right. pin 3 not connected. problem solved. 

but then another question. what in the world was pin 3 used on the old part ? htv p1501 ? they use half a photo resistor or ?

--- In PolySix@yahoogroups.com, "backshall1" <backshall1@...> wrote:
>
> 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
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>