Would you mind expanding on this a little? I am asking because it was recently discovered there are some bad CDXL boards.... I may have a couple, or I may not. Regardless, my assembled versions don't work. Compound the potential for a bad board with the ambiguity of the correct orientation of the Vactrol, and the cause mine not working is potentially compounded, and certainly frustrating.
If I understand it, half the vactrol is just an LED, and the question I am asking really is about the orientation of the LED in the board. If I understand you, you are saying generally the short leg of the LED is the cathode, and it would go in the square hole. Is that correct?
In the OP, you can see the printing on the opto-isolator device and that the printing of "XVIVE" & "LED+" is oriented on top. That "plus" symbol, indicates which side is the anode. The anode wants the positive voltage and the cathode wants to be grounded. So, when you insert the photocoupler, you want that printing to face down. The image of the PCB clearly indicates that the round hole is directly connected to the ground plane. The long leg of the LED side should be inserted in the square pad insert point. That is an industry standard. Most square pads are indicative of either positive for polarized components, or pin #1 for pots, ICs and other multi-legged creatures. The LDR side has no polaris orientation - just the middle lead needs to go into the middle hole for that part. See the attached image for physical orientation. (While image provided does not indicate which lead is longer, and the photo of the XVive 5V4/2 has no dimple on the body to identify the cathode, the printing on the device body indicates the positive lead (anode) of the LED inside the device body.)Alright, something is amiss here. My boards definitely do not match the rendering. In the rendering, there is a trace between the 10K and 100K resistors, implying there should be continuity between them. My boards do not have this trace. But on the back side of mine, there is trace that connects the 10K and other 10K resistors, as shown below with my red circles. And this doesn't seem to match any of the schematics I've found online.
View attachment 2091
Picture: my boards have a trace (on the back side) that creates continuity between the 2 red circles. Mine do not have the trace between the 10K and 100K resistors.