[help]lenovo thinkpad 16s gen 2 TOTALLY DEAD

[phantomEVO]

Hi to all! thinkpad p16s gen 2 totaly dead. i have only 5v on both ports.

pd controller is tps65994

i don't know where to start: could you help me? thank

Schematic & Boardview - https://www.badcaps.net/forum/troubl...atic-boardview

[reformatt]

This has a NVDC power supply, so should boost the USB-C 5V to around the battery voltage. So first thing to check is for a short on the B+ rail, then presence of your +3V LDO. 20V negotiation is irrelevant.

[phantomEVO]

hi reformat thank you for your answer...

i don't know what is a nvdc power supply

battery has very very low voltage

on the pd controller i have

5v ON DOCK_VBUS20

0v on Vin3,3

5v on Charger in

3,3v on Vcc3 Ldo

now what can i check?

Thank you

[mon2]

https://forum.monolithicpower.com/t/...power-path/162

[phantomEVO]

Thank you...so ..what could be the next step?

[mon2]

0v on Vin3,3

?? Suggest to use the exact netname from the schematics otherwise it becomes a game of 'Where is Waldo?'. Our PCB designer does the same often and we have to spend time to hunt for the new label created in his head.

Where was the above measured?

To me, if the Vbus voltage is not 20V then there is something wrong with the PD controller. The PD controller is often a stand alone negotiator for the power delivery contracts. Provided the firmware is ok and the pd controller is not defective, the Vbus rail should be @ 20v, supplied by the power adapter.

Any power rail that is @ 0v or not in the normal range, test its resistance to ground (without power to the board) to check if the rail is shorted or not.

[phantomEVO]

all measurements done on pd controller no shorts on the pd controller

with vin3,3 i mean vin_3v3

[mon2]

This is of concern since the rail is also used by the PCH (CPU).

Remove all power. Meter in resistance mode. Measure the resistance to ground of VIN_3V3. Checking if there is a shorted part on this rail. What is the exact resistance in ohms?

[phantomEVO]

25k

[phantomEVO]

even with another pd controller, i have the same behaviour

[phantomEVO]

ok i0ve disconered something .... i have short on pl5301

i've removed the coil and the short is on the right side (pin 1)

this side is connected to 2 mosfet and charger ic....now??

removing mosfet pq5302 the short is gone...should i replace it? its is an n-channel 30v 85a mosfet...should i mount the same identical?

[reformatt]

This is a buck/boost converter power supply. You will get 5V on USB-C initially, then it will be in boost mode to get your B+ voltage (which should be around the same voltage as marked on the battery, and not +19V). The PD controllers will only negotiate 20V once you have some ancillary power rails come up. But for that you need the main power supply to be working and providing B+. When you get 20V, then the power supply goes into buck mode and reduces the voltage to that of the battery.

All of this is in Piernov's sticky at the top of the forum BTW and some troubleshooting steps.

https://www.badcaps.net/forum/troubl...arging-circuit

You haven't mentioned what the B+ voltage is, if any. Very rare for these MOSFET's to fail.

[phantomEVO]

thank you for your amazing explaination i tought it would work like macbook!

for "b+" you mean the voltage of the battery? or the voltage of the battery measured on board while charging?

[reformatt]

Mac's work similar. As I said, 20V is irrelevant as a starting point in these designs with a buck/boost converter.

Are you even looking at the schematic? B+ is the main power rail. Should be around the same as what the battery voltage is. 12V or so.

Just had a dead Lenovo on the bench. No current draw at all. Just needed batteries removed, along with the CMOS battery. So just needed a BIOS reset, so make sure you cover the simple stuff first.

[phantomEVO]

thank you for your amazing reply!!!

i'm starting to understand how it works...a little bit complicated for me...but i'm trying to understand.

but why don't you take attention to what i have found?

short on pl5301: following the path, i have removed a mosfet (pq5302) and the short is gone...now my problem is to replace it. it is 30v@70a!!!!

do you think that this mosfet could be the reason of the main problem?

[phantomEVO]

so, i've temporaly replaced the mosfet with a irf3205

https://www.alldatasheet.com/datashe...F/IRF3205.html

connected the charger only i have had charging led

so i have installed the battery, and press the power button

i have seen white led from the power button,then suddenly i have heard my power supply "switching" and notebook power off itself (ive seen that my power supply was set to 20v 1,1a, so i have think to connect it's original power supply (19v 3,25a) but nothing.

no charging light, no 19v on amp meter , nothing. motherboard dead like before.

the shorted path where i have changed the mosfet, is not shorted