Lenovo Yoga 910 Charging Problem

[mgrharry]

Re: Lenovo Yoga 910 Charging Problem

I don't see any mosfets in the immediate vicinity of where the DC in ribbon connects but here's a pic of the closest ones


Application of freeze spray to these doesn't reveal any obvious faults.

Spec sheets can be found here:
https://www.digikey.com/product-deta...5-1-ND/3061123
and here
https://www.digikey.com/product-deta...506-ND/3973606

[mgrharry]

Re: Lenovo Yoga 910 Charging Problem

One more thing I noticed: the system will not power on or show any signs of life when AC power only is connected. However if the battery is connected and then the AC adapter is connected the charging light on AC adapter board starts blinking and the system powers on by itself.

[mgrharry]

Re: Lenovo Yoga 910 Charging Problem

Yes, the system powers up and runs off battery no problem. I do have a DC power supply but I'm not sure where on the motherboard to apply power.

Here are some pics with the DC in board and ribbon connected.



Negative clamp applied to ground obviously but where to apply the positive clamp?

[mcplslg123]

Re: Lenovo Yoga 910 Charging Problem

Dear mgrharry, start with pwer fets just after dc jack. Check the mosfet datasheet and see whether you are getting correct gate voltage on pin4 of fets. next to check is charging ic voltage. You can download datasheet for charging IC and help yourself in diagnosis. Non availability of schematic is not the end of road in troubleshhoting as long as you are focussed and keep your head cool.

[BlueMidnight]

Re: Lenovo Yoga 910 Charging Problem

You never explicitly stated whether it powers up on either battery or AC adapter power. In other words, is the board dead or does it simply not charge properly?

[Stevie2001]

Re: Lenovo Yoga 910 Charging Problem


Get it from ebay cheap and very good.
having a dc power supply would be a good thing as it can inejct amps into the bad componant witch will heat up and by using your fingers you can quickly locate the bad part.

Just connect the dc power supply red black to dc then set voltage i to 1v and amps to 0.50 and slowly increase it as your feeling it with fingers,look up on youtube how to use dc power supply to find short.
Thermal camera is best,it takes seconds to locate it and fix it,so in future get this fast.

watch this how to use dc power supply to find short
https://youtu.be/CW87dyYIimE?t=8m44s
time 8:45

You mentioned you have freeze-spray spray one side and connect the power wire and se witch part on board gets visible first assuming the board is iced up.



you can buy cigeratte lighter petrol $1
and add it one one side of the board connect power and se witch part gets dry fast.
the good thing about this is it don't evaporate quicky and also when the petrol is over a component and its bad it will dry up than when you unplug the ic will get covered with petrol again automaticly like jelly very works good.

watch this and so it helps
https://youtu.be/CW87dyYIimE?t=10m
time 10.00

[mgrharry]

Working on a Lenovo Yoga 910-13IKB, model name 80VF. This unit had liquid damage to the USB C DC in board and ribbon that was preventing it from charging properly when the adapter was plugged in. The unit would sometimes not detect the charger at all, other times it would rapidly cycle from charging to not charging (about every 1-2 seconds) when the adapter was plugged in. There was some corrosion evident the DC in board and ribbon so I replaced them both with a new unit however the same symptoms still persist in the form of rapid cycling between charging / not charging. Clearly there is some component damaged on the motherboard itself however there is no visible corrosion or damage to the motherboard itself.

I have a hot air station and microscope so if I can locate the defective component I can probably replace it but I can't locate any schematics for this board and other than haphazard application of freeze spray in the general vicinity of where the ribbon for the DC in board connects, I'm not sure where to start.

You can view photos of the board below.

Any tips would be greatly appreciated.