Originally Posted by
Tyrbiter I received the KMV78Y update this morning, and finally got round to checking the contact voltages after applying it.
The centre contact is now at 0V as it should be, the one next to the ground contact (reset switch end) is showing 1.755V and I can feel a tingle with my tongue across those contacts. That doesn't seem right to me. Originally both these contacts measured 1.7-1.8V, so the centre one is definitely powered off now.
I will be interested to hear what you get from them about a replacement, the 2 contacts on mine, especially the centre one, are pitted and missing not just the gold plating but also noticeable amounts of the base metal.
I have been provided with a replacement by the Google Play store, and have been using it for about a 10 days, unfortunately the replacement is behaving the same way as the original. I applied the KMV78Y firmware update as soon as I received the new watch, I did not wear it at all without the data pin voltage 'fix'.
The contact next to the ground (nearest the reset button) is still showing 1.755V on a high impedance voltmeter and I can see today that the gold on this contact is partially gone and the metal below is starting to pit and corrode away. This is really very disappointing.
Some more investigation reveals that the contact next to the ground is the spare contact on a micro USB connector, sometimes known as 'ID' and used for various purposes. In this case, a similar Qualcomm design I found on the web has the signal connected to this line called FORCE_USB_BOOT, so it's used to put the SoC chip inside into a mode where it boots differently. I suspect that means that there is no way to turn off this voltage without a hardware change inside the watch.
Checking the charging dock reveals that it is a simple straight through design, the matching pogo pin is not connected to either ground or apparently anything else. Shorting the ground contact on the watch to this adjacent contact via an ammeter reveals a current of 8.8uA flowing, so shorting the pins together would reduce battery life by a bit less than 0.1%. A better solution is to carefully cover the ID contact with something non conductive, glue or paint, and prevent it from touching the skin.
This means there is a simple fix if people are prepared to make this small modification; in my case the contact is being corroded away so it is worth doing it.
I've had mine for 3 days and had no signs of corrosion or pain-It's a colder country here so less sweat. It seems likely it's that. To be safe I put a spare dbrand skin I had left over from my N4 (they sent me two because my original didn't get delivered in the Christmas Rush) just beside the pins to keep it lifted up. If it starts corroding I might put it over and try to get a NATO strap. Fairly cheap on ebay
