10-18-2018 06:48 AM
11-20-2018 05:52 AM
I too had a not charging yoga700-14isk on my desk got from a friend. after a longer resarch i came to this thread
which pointed me to the right direction.
Summary: The usb adapter is a dual voltage atapter 5v normally without any yoga connected (or e.g. a cellphone) and ca. 20V if the additional line (the adapters usb has 2 outer additional fingers - lets name it 5/20V control-line further) is pulled to 3.3V by a voltage divider (200Kohm to gnd) in the yoga in case pluged into.
In my case (which took me several 10H to realize) the input resistance (Yoga side) of the additional 5/20V control-line was 2.5Kohm instead 200K. The reason was that the parallel connected PD104, actually a TVS-ESD protection Diode - was blown ( a very tiny sod-882 device which I removed as first step -> 200Kohm -> charging was working again.
So my advise: check the input resistance first on the 5pin-MB connector in disconnected Yoga Battery and Power adapter situation to rule out the fault I had.
Actually, alternatively you can check the adapter by asserting 3.3V to this control line by a external power source (with e.g. a serial resistor of e.g. 5K) and check with the voltmeter that the Adapter output-voltage changes from 5 to 19-20V on the USB Vbus lines- normally pin 1,4.
Because The control line(s) are the 2 additional outer pins we are counting 1-6 on this special adapter usb-socket. therefore pin 1,6 are the control line - connected together by the charging cable, but only one used at the adapter side. pin 2,5 the usb voltage (5/20V). Pins 3,4 data bus - unused and not connected at the adapter side.
Maybe I'll give some extra pictures if of interest.
In order for easy acces and checking the voltages/resistances - the MB-power(-USB) connector PJP1 pins are as follows:
Note: seen from above and connector at right side and counting from top to bottom.
1 - GND
2 - Control line (should be 3.3V if adapter connected)
3,4 - USB Data Bus
5 - +5/20V
good luck !