Lenovo Yoga 710-14IKB only turns on with AC present

[philuk86]

Hi guys, I have a Yoga 710-14IKB that will only turn on (cold start) when plugged in. Once turned on I can disconnect the AC and it continues to run and the battery charges fine. Restart on battery is also fine.

If the laptop is switched off and i plug in the power cord the charging indicator LED will come on for a few seconds but then it turns off, i.e. it only charges when switched on.

I did a quick check with a multi-meter and there is no 0v at VCC on pin 8 of what i believe is BIOS ROM (W25Q64FV) when switched off-battery only.

Anyone have any ideas?

Thanks Phil

[MJ-meo-dmt]

Re: Lenovo Yoga 710-14IKB only turns on with AC present

Should check all parts of the power rails. Report all voltages here. If you can maybe even take a nice high quality photo and color in the voltages as you find them.

Here is a power rails chart from a Yoga 460. See what's different from AC only and Battery Only.

[piernov]

Re: Lenovo Yoga 710-14IKB only turns on with AC present

Did you try to replace the battery yet? If it thinks the battery is too low when off with AC adapter disconnected, it won't turn on (BATLOW# signal low going to the PCH for example).

[philuk86]

Re: Lenovo Yoga 710-14IKB only turns on with AC present

Yes both of the batteries I have exhibit the same problem.

The 3.3, 5 and 1.05v are on with the AC but none with the battery alone.

[philuk86]

Re: Lenovo Yoga 710-14IKB only turns on with AC present

After a bit of digging it looks similar to an older LA-A921P. I think PQ305 and PQ306 are the high and low drivers (on the back of the board) and PQ304 is connected to FF201 from the battery. These are the measurements i get AC, battery and AC+battery.


On AC

PQ305
1. 8.4v
2. 8.4v
3. 8.4v
4. 10v
5. 20v
6. 20v
7. 20v
8. 20v

PQ306
1. 0v
2. 0v
3. 0v
4. 0v
5. 8.3v
6. 8.3v
7. 8.3v
8. 8.3v

PQ304
1. 0.21v
2. 0.21v
3. 0.21v
4. 0v
5. 0v
6. 0v
7. 0v
8. 0v


On Battery

PQ305
1. 1.5v and falling..
2. 1.5v and falling..
3. 1.5v and falling..
4. 0v
5. 6v and falling..
6. 6v and falling..
7. 6v and falling..
8. 6v and falling..

PQ306
1. 0v
2. 0v
3. 0v
4. 0v
5. 0v
6. 0v
7. 0v
8. 0v

PQ304
1. 0v
2. 0v
3. 0v
4. 0v
5. 0.2v
6. 0.2v
7. 0.2v
8. 0.2v



On Battery with AC plugged in

PQ305
1. 9.56v
2. 9.56v
3. 9.56v
4. 11.5v
5. 20v
6. 20v
7. 20v
8. 20v

PQ306
1. 0
2. 0
3. 0
4. 0
5. 9.6v
6. 9.6v
7. 9.6v
8. 9.6v

PQ304
1. 0.2
2. 0.2
3. 0.2
4. 0
5. 8.6v
6. 8.6v
7. 8.6v
8. 8.6v

[on/off]

Re: Lenovo Yoga 710-14IKB only turns on with AC present

What kind of charging chip?

[philuk86]

Re: Lenovo Yoga 710-14IKB only turns on with AC present

What kind of charging chip?

I think its this one (PU301 very bottom left on back of board) 955 20AHRZ W632NB

http://www.alldatasheet.com/datashee.../ISL95520.html