Help please..Lenovo ideapad 5 14itl05 power and charging problem

[Dr.d]

I have a lenovo ideapad 5 14itl05, board LA-K321P, That will only power up on Battery only, or with battery disconnected and power adapter only. If battery is connected and usb-c power plug connected. It only works on battery and will not charge. I can however force it to charge by connecting the battery from a disconnected state while the power USB c plug is powering the laptop.

Additionally....to add to this strange situation. The usb-c power plug ONLY works to power the laptop on one side when inserted into the boards power usb c plug. If you rotate it 180 degrees, the board gets no power. The power adapter is confirmed good and tried another with same results! Any help would be greatly appreciated.

[mon2]

Hi. You have either a physical problem with the USB Type C connector or an electrical one linked to the side that is non-functional.

Start with inspecting the side that does not function. It will help if you have a USB Type C meter (Amazon, Aliexpress) to place between the power adapter and this target logic board. The USB Type C meter will offer details on the voltage and current draw by the logic board. Being power delivery based, the CC1 and CC2 pins on the USB Type C connector are used. Each single pin is used for communicating with the power delivery controller onboard this laptop.

Consider to use IPA and a Q-tip to clean up the contacts on the side that is not working. If the contacts have been BBQd then the connector may need to be replaced or just not used by the user.

Next, focus on the side that does function. You will need to review the DCin mosfets in the power path from this Vbus voltage rail onto the logic board.

Remove all power. Meter in resistance mode (not DIODE mode).

Measure the resistance across the mosfets to check if they are leaking.

Review the following mosfets (PQB13, PQB1, PQB2) by checking:

source (1-2-3) & drain (5-6-7-8) ; place one meter probe (either color) onto 1 or 2 or 3; other probe on 5 or 6 or 7 or 8
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. We are checking for a low resistance reading which means the mosfet is defective and needs to be replaced.

[Dr.d]

Thank you kindly for your input/help mon2! I do have the usb c meter and on the side that doesn't work, nothing displays at all. The working side I get the 20v and low amps draw. I was going to check the components that you suggested but am having a hard time locating them on the board. I have schematics but no Boardview. Do you happen to have that for this laptop motherboard so I can locate the components you suggested checking? Thanks

[mon2]

Yes, see attached.

[Dr.d]

Hello Mon2....I took the measurements and wanted to let you know what I found. They seem to be okay and nothing too low. But wanted to show you and see what you thought I might check next. Here they are..thank you!

PQB13 > Source to Drain: 2.4M ohm
Source to Gate: 3.2M ohm
Gate to Drain: 6.8M ohm

PQB1 > (Pin1=Gate1),Pin2,3,4=Drain; Pin5,6,7=Source; Pin8=Gate2
Source to Drain: 1.58M ohm
Source to Gate2: 207k ohm
Source to Gate1: 275k ohm
Drain to Gate1: 1M ohm
Drain to Gate2: 1.5M ohm

PQB2 > (Pin1=Gate1), Pin2,3,4=Drain; Pin5,6,7=Source; Pin8=Gate2
Source to Drain: 2.0M ohm
Source to Gate2: 123k ohm
Source to Gate1: 153k ohm
Drain to Gate1: .8M ohm
Drain to Gate2: .6M ohm

[mon2]

The source to gate readings of PQB1 and PQB2 are considered to be low.

Do you have hot air tools to remove PQB2 off the board for testing?

Do not, repeat do not power up without the PQB2 mosfet. It is required to dial down the high voltage to a safe lower voltage for the main power rail.

[Dr.d]

Okay, thanks. ....I do have tools. Once I remove should I re-measure them out of circuit? What value should the source to gate have normally?

[mon2]

A good mosfet should be with a higher resistance for each permutation of the same tests. Megaohms is ok.

reference:

https://electronicsbeliever.com/how-...-is-defective/

[mcplslg123]

To me,it appears to be a simple worn out usb-c jack which needs to be replaced.Most of the motherboards usb-c jack needs them to be replaced after a usage of almost 2 years.

[Dr.d]

Okay, thanks mon2, I'll dig into that and check it out.
mcplsmg, thanks for your input. I have one on order now to try.

[Dr.d]

Mcplslg123...... Just wanted you to know I did replace the USB-C , it didn't make a difference. Same issues...only receives 20v on 1 side of the input plug. If you rotate it to the other side 180 degree. Nothing on the meter and laptop doesn't not power up. Strange stuff. I cannot find any shorts on the board

[mon2]

Review the ESD protector @ UT2. Remove all power. Meter in DIODE mode (not resistance mode). Red meter probe, yes red, to ground. Black meter probe to point to test.

Measure on pin # 12 (TCP0_CC1) and then #11 (TCP0_CC2) - each to ground. Post each measurement. Checking to see if this ESD device is shunting the side that is not working.

[Dr.d]

Thanks mon2.... I just checked and get .423v on each #11 and #12

[Dr.d]

I'm thinking that one of the input lines on the bad side is not getting the signal to fire up the 20v. I also don't know if it is related to the charger not working together with the battery unless you disconnect the battery and then connect it while the adapter is plugged in (The good side).

[Dr.d]

I also check DT7 and DT8 diodes. They both check good on Pins 1,2,4,5 to ground at .637v

[Dr.d]

Mon2, do you know what signal line on the USB c port, into the motherboard triggers the board to turn on the adapter to feed it 20v? I'm thinking that on the one good side circuitry is getting that signal. The other side no. My input meter doesn't even light up on the bad side. 20v on the good. Thank you.

[mon2]

Yes, it will be CC1 on one side and CC2 on the other side. These CCx pins are used for the USB Type C power delivery communication. If not done already, remove all power. Meter in DIODE mode.

Measure the DIODE mode readings of each pin on the USB Type C connector with red meter probe to ground; black meter probe to the pin to test. Make a table of these readings for the good side and then compare the same measurements against the non-working side. There must be a difference.

[Dr.d]

Will do...thanks!

[Dr.d]

Hello mon2.... I went ahead and did the diode checks on the USB-C pins ... I did not find anything that seemed off at all and both sides matched with the Diode check voltages. But it did lead me to check the Diode Array chip. DT16 and DT1. DT16 ic has the CC1 usb c pins going to it. I check it out and the Diodes all check out with the exception of pins 2= ground and pin 5 =Vcc . I cannot seem to find where the Vcc goes to or comes from on that pin. Looking at the schematics it just says Vcc and on the Boardview I click on pin 5 of the DT16 ic and it doesn't show any connections. Anyways...Pin 2 and pin 5 represent a Zener Diode. I took it out of the circuit/removed from pcb and it shows shorted out of circuit. What do you think?

[mon2]

Good stuff. For sure this component can shunt the operation of the USB Type C device. For now, you can leave this part off the board. From our experience, such TVS ESD devices are designed for a flow-through PCB layout. Meaning that the signals travel on the PCB to a protection device, touch the part for protection and carry on. Respectively, the part is not required for the flow through of the signals but of course the protection is lost when this part is removed. Also, this part is sacrificial and it jumps into a live volcano to suppress the ESD transient. A high enough transient can kill this part but it has saved your more sensitive logic components but now this part will need to be replaced.

The pins # 2 and # 5 are most likely spiked to hidden layers of this multi-layer PCB. Often, the ground plane and the power planes are sandwiched inside of the PCB layout and then mated with pcb vias (small diameter pads).

Keep this ESD device off the board and test again.