LA-B921P Yoga 3 11 - No power

[magneh]

Hi

I have a Yoga3 11 inches with no power.
I managed to find the schematics, here in att.
I have no voltages in any of the main coils, and no shorts.

When charger connected I get 5V as you can see on the image here.
But 0V at VIN, diode mode to ground 2.33V there, seems too high...
Resistance to ground 256kohm

What would be the approach here?
Are the 5V normal on these ? and then they boost to 20v?
Kinda confused with this particular one, and I see the charger is rated to 5V and 20V.

Board had no liquid damaged. One burned component,U52 . Removed it , its USB 3.0 port related, and no shorts in any pins,

Any guidance is appreciated! thank you

[ktmmotocross]

Re: LA-B921P Yoga 3 11 - No power

JDCIN looks like a normal usb connector, with data lines and id line, so 5V is normal

but on other page VIN is regular 19V with bq charger ic.

it is really weird

[brew99]

Re: LA-B921P Yoga 3 11 - No power

I think you need to concentrate on the VIN section (page 27), and ensure you get your 19V rail. Not exactly sure what that JDCIN1 section is, but it's not boosting, just enabling 5Vusb power.

[khaahk]

Re: LA-B921P Yoga 3 11 - No power

check esd protection diode, pd105.