Lenovo 730-15IWL No energy

[dagolard]

Hi everyone.
I have a Lenovo Yoga, where the charging doesn't work.

- No charging/Battery LED, even with battery disconnected
- power supply is tested and okay (65W and 135W version tested)
- onboard fuse PF202 is okay
- until cable I can measure the voltage (Clip22 removed, measured the wires).
If I press power button, a little "click" sound from speaker appeares. Seems he want to start, but not enaugh battery.

I think it is the FET PQ302 (see picture). Looks a little... defective in one corner.
Can anyone tell me what type it is?
How can I check, if it is that part?

Regards Holger

Redacted because of horrible english

[mon2]

Pour some ipa (alcohol) onto the part. This will enhance the topside markings. Share a good pic or all markings. Then google should help to find a datasheet for this component. This mosfet will be an n-channel or p-channel mosfet.

To test if the part is ok or not, remove all power. Meter in resistance mode.

Measure the resistance across the mosfet.

Source (1-2-3) & drain (5-6-7-8)
source & gate (4)
gate & drain

pick a pin from each group. Post each measurement in ohms.

[dagolard]

Okay. Will do it in evening.

[mon2]

NVM. I think I found the schematic and have the details for PQ302.



PQ302 is an N-channel mosfet. This implies that the gate pin must be higher than the voltage being passed between the source & drain pins. This part is acting like a solid-state relay / switch and will fully enable if the gate voltage is ~25v (since adapter voltage is ~19v).

Do perform the resistance checks as above (without power to the board!!). This will allow us to confirm if the mosfet is defective or not. Repeat with the 2nd DCin mosfet. Often, it is the 2nd DCin mosfet that is defective. If either of these mosfets is defective, the defective mosfet will stop the other one from working as well because they are sharing the gate (driver) pins.

Do review the charger bible as per the sticky above by @piernov.

Post your measurements when convenient.

[dagolard]

Source-Drain: 1.1R
Source-gate: 2.1R
Gate-Drain: 2.4R

[mon2]

Post the details of your meter face for the above measurements. Is the meter an automatic scaling type or manual select version?

1.1R = 1.1 ohms?

Better if you post a pic of the meter face to show one of the above measurements.

[dagolard]

R is Ohms. Sorry, sometimes we are used this naming in the industry.
I always cleaned up my workpace. It is a automatic scaling multimeter (see photo). Not the newest, but not bad at all.

[mon2]

The meter is auto-scaling. Take a pic of one of the measurements so we can confirm if you are truly @ 1R1 = 1.1 ohms which is a serious short. Suspecting you are not - check the top right corner of the LCD to note the units of measurement.

[dagolard]

Guys, maybe I´m not good at newer high integrated electronics (I´m 62 and learned the electronics job in 1982) but I can read a multimeter. 😉
The difference (1.3 ohms) probably depends on a little shakey fingers while measuring AND make the picture with two hands only. Was between 1.1 and 1.2 most time.

[dagolard]

So it looks like I have to get a EMB04N03H. 🤔
Will look on monday in our company. Maybe there are some in the "assortment drawer" of our electronic engineers left over from older projects.

[mon2]

This part is shorted. Flux and remove the part. Then repeat the testing with the part on your work bench. Very likely the part will remain with low resistance = defective.

Repeat testing with the next dcin mosfet. It may also be defective.

[mon2]

The part can be replaced with many others. Check almost any motherboard for n-channel mosfets of the same physical size.