820-00239 - No power

[nameless]

Hey everybody

I've got a 820-00239 with no power

HISTORY : a customer brought this laptop with no power issue. He said that first there was image issue when moving the screen, but he was able to use it with an external monitor. After that, he said that the laptop stopped powering on at all.

WHAT WAS DONE : I disassembled the motherboard and spotted some corrosion around UB400 chip.

So I think in first place there was an issue with the flex from the screen, because it worked only in certain position - and I can fix it later if I manage to power it up ))

MEASUREMENTS :

I measured some pins on UB400 :

PP1V8 LDO - 1.8v
PP3V3 LDO - 3.3v
PP1V1 LDO - 0v
PP1V8 LDOA -1.8v
USBC_TB_CC1 - pulsing from 1V to 2V like a crazy

AMP meter

on power it takes 20.41V from the wall and AMP go up to 0.8A and drops to 0.40A

Is the UB400 - CD3215A dead ?

You'll find some pics around UB400 corrosion

Thank you for your support

Best regards

 

[2informaticos]

You must clean the area and replace damaged components.
All USB-C ports have the same behavior?
Check all in both connection ways.

 

[nameless]

Hey thanks for your support

Ok I cleaned the oxidized area

All four port have basically same behaviour : it goes up to 0.9amp then drops to around 0.37 amps and drawing 20.41V

I don't see any damaged components, except that PP1V1 LDO pulls 0v instead of 1.1V on UB400,300 U3200,3100

here are all LDO's from all ports :

UB300
PP1V8_UPC_TA_LDOD - 1.8V
PP3V3_UPC_TA_LDO - 3.3V
PP1V1_UPC_TA_LDO_BMC - 0v
PP1V8_UPC_TA_LDOA - 1.8v

UB400
PP1V8_UPC_TB_LDOD - 1.8V
PP3V3_UPC_TB_LDO - 3.3V
PP1V1_UPC_TB_LDO_BMC - 0v
PP1V8_UPC_TB_LDOA - 1.8v

U3200
PP1V8_UPC_XB_LDOD - 1.8V
PP3V3_UPC_XB_LDO - 3.3V
PP1V1_UPC_XB_LDO_BMC - 0v
PP1V8_UPC_XB_LDOA - 1.8v

U3100
PP1V8_UPC_XA_LDOD - 1.8V
PP3V3_UPC_XA_LDO - 3.3V
PP1V1_UPC_XA_LDO_BMC - 0v
PP1V8_UPC_XA_LDOA - 1.8v

 

[2informaticos]

1V1 LDO should appear only on the powered port...

 

[nameless]

oh okok then I do have it )))

Should the fans startup when plugin in the mb ?

 

[nameless]

Because I don't have fan spin, nor I have an image on external monitor. The monitor seems to detect HDMI output as a source, but external monitor screen remains black

 

[2informaticos]

Check L7210/20 voltage after 15 seconds.

 

[nameless]

L7220/10 - 0.64V

 

[2informaticos]

Looks like board is booted.

Disconnect internal LCD and test external video again.
Also check for USB activity.

Fans will run when CPU gets hot.

 

[nameless]

ok thats cool it boots at least )

All tests were done with the mb outside the case, so normally all cables are already disconnected

But i'll try again.

What kind of usb activity should I expect ?

 

[2informaticos]

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

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