CDXL Vactrol Orientation
- Thread starter Bravin Neff
- Start date
DGWVI
Well-known member
Generally, the short leg (cathode) would go in the square hole. I think it's just this board that has it flipped.
Bravin Neff
Member
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?
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?
DGWVI
Well-known member
I'm looking at schematics for this circuit found elsewhere on the web, and they have the cathode of the LED running to ground. The round hole from the LED portion on this board is connected to the groundplane, so that would be cathode according to the schematics.
I could also be completely wrong, and PedalPCB may have worked his board from a different schematic than I've seen
The Vactrol is actually an LED and a Light Dependent Resistor (LDR) rolled into one. The side with two holes is the LED, the anode being marked with the + symbol. The other side is the LDR, in this case it has three legs, similar to a potentiometer.
Most PCBs will have the LED oriented so that the cathode goes to the square pad. This particular board seems to be one exception.
DGWVI
Well-known member
I'd still wait for PedalPCB to chime in just to be certain
Bravin Neff
Member
Is it possible to destroy a vactrol by installing it backwards? Since the LDR side seems more or less like a potentiometer, I guess I'm really asking about the LED side. Going by your comments above, I installed the vactrol in backwards and powered it on.
Bravin Neff
Member
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.
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.
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.
Cybercow
Well-known member
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.)
Hope this helps.
I Love Music
New member
May I suggest, insert a regular red LED in the holes without soldering, to test the VACTROL orientation for actual functionality. This is how I discovered I had a bad board in the first place.
Chuck D. Bones
Circuit Wizard
Let's all buy boards before the build docs are published! You guys are crazy. 
Bravin Neff
Member
Let's all buy boards before the build docs are published! You guys are crazy.
1. I bought it before I realized the build docs weren't published. After all, it was for sale.
2. I didn't realize I had any reason to be worried about anything.
Lesson learned.
Chuck D. Bones
Circuit Wizard
On the bright side, it does provide an opportunity for us to hone our reverse-engineering skills. 
benny_profane
Well-known member
Thanks for this. Is this for the forthcoming revised board? Any updates on the replacements?
