Lenovo T570 not turn on

[arber1232]

Re: Lenovo T570 not turn on

i not understand what you need





Is normal to heve 0v in other side R6905?


I see VCC3M missing in board

[mon2]

Re: Lenovo T570 not turn on

No it is not. Confirm that R6905 is onboard.

Remove all power -> meter in resistance mode -> check the resistance between the 2 pads for R6905.

This missing voltage is used to power THE1B core.

[arber1232]

Re: Lenovo T570 not turn on

This is boarview

https://www.badcaps.net/forum/showthread.php?p=1235558
.

[mon2]

Re: Lenovo T570 not turn on

Check if R6905 is now a broken / open trace.

[arber1232]

Re: Lenovo T570 not turn on




Se resistence in photo

The resistot value in board is 385kohms

[mon2]

Re: Lenovo T570 not turn on

R6905 (pin #2) to VREGIN20 should be ~0 ohms, according to the schematic.

R6905 value - not sure. DO not bypass R6905 till we know the value for sure.

[arber1232]

Re: Lenovo T570 not turn on

Yes from VREGIN20 to pin 2 R6905 is ohms

[mon2]

Re: Lenovo T570 not turn on

What resistance do you measure for R6905? Remove all power. Measure across the R6905 pads.

[arber1232]

Re: Lenovo T570 not turn on

Value change is not stably start from 10 Mohms

[mon2]

Re: Lenovo T570 not turn on

This is not a good value for this resistor. This resistor and the one below it work together to lower the adapter voltage. Acting like a voltage divider.

What is not known at this time is the true value of this resistor.

Is the resistor below this one in the schematic stuffed on the logic board?

At this time, we do not want to bypass R6905 till we know more about this design. The target chip can be damaged if the power rail of ~19v (adapter) is applied.

[arber1232]

Re: Lenovo T570 not turn on

R6901 and R6902 Value is 10ohms and voltage is 11,96v

[mon2]

Re: Lenovo T570 not turn on

What about R6908 resistance ?

R6905 & R6908 work together to build a voltage divider to lower the main voltage rail to a safe value for THE1B.

[arber1232]

Re: Lenovo T570 not turn on

What about R6908 resistance ?

R6905 & R6908 work together to build a voltage divider to lower the main voltage rail to a safe value for THE1B.

R6908 is 1.2 Mohms

Who enable vcc3m signal ? becouse is missing

[mon2]

Re: Lenovo T570 not turn on

Then r6908 cannot be a voltage divider resistor with such a high resistance value. If this THE1B is able to support a high VCC power rail, only then we can consider to short the missing resistor. Is this a part on the logic board or a pcb trace? Can you post a clear pic of this area?

[arber1232]

Re: Lenovo T570 not turn on

[arber1232]

Re: Lenovo T570 not turn on

CAn i help me ?

[arber1232]

Re: Lenovo T570 not turn on

when i replace R6905 with R6908 laptop turn on . on side R6905 is 12 v an other side is 7.5 v . I remove R6905 and resistor is bad not value . Can i replace R6905 with value 1.2Mohms ?

[mon2]

Re: Lenovo T570 not turn on

R6908 is too high of a value.

Can you post a pic of your meter face while you are measuring r6908?

To me, at 1.2 mega ohms, this circuit leg cannot function.

[arber1232]

Re: Lenovo T570 not turn on

i find another board For Lenovo T570 and resistor R6908 and R6905 is 1Mohms Voltage one side is 5 v other side 12v

[mon2]

Re: Lenovo T570 not turn on

Is your meter auto-scaling in the resistance mode or is it a manual setting?

Post a pic of this setting used on your meter for these measurements.

Need to be sure the resistance readings are correct.