The pinMode and digitalwrite should be to "buzzer_IO, OFF" not POT_DIO. This also occurs elsewhere in the code, I copied and pasted the original and it definitely doesn't work.
This is really bizarre, I still have the window open from when I tested it this morning and the code is correct. The posted version must have been an unfinished version. I've now updated the sketch with the version I have and should work fine. We've only just put this product on sale so you are probably the first person to use this code.
I think I've spotted the issue with LED D1 being permanently on. The existing LED on the UNO uses a 5V output to switch it on whereas your LED relies on a GND to switch on the LED this means that there is current flow between 5V and Gnd through both LEDs.
The section of schematic you have posted appears to be from a really old design (pre 2011) and Uno's built to reference designs for the past few years do not have the LED connected to pin 13 in this way. See here for reference:
http://arduino.cc/en/uploads/Main/Ardui ... ematic.pdf
This would indeed explain why you are having the problem with this LED, but your board would have to be very old and not conform to at least the last two major Uno revisions?
I don't directly deal with the eBay messages but you should expect a reply from someone today.
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