Lenovo ThinkPad X1 Yoga 4-го поколения — мертвый ThinkEngine (чип EC)

Hi guys. I bought this one to see if I can fix it to use.

Immediately under the thermal camera I can see the ThinkEngine is glowing red hot - clearly an internal short. Absolutely zero corrosion or water damage anywhere.

Two pins shorted have low impedance - PGPIO0 (5 ohms), RD0_ON/5MUBAY (0.7 ohms).

It is the BD4179 (the schematic has it labeled as a TC62D518FTG_BD4179MW V-E2_W QFN56_7X7). I can of course solder a replacement IC, but can find no information on whether its self reprogramming. I do not see a seperate ROM chip, I understand these have internal ROM, and on some laptops, soldering a blank one means the motherboard will self reprogram it?

Does the same apply in this scenario? Can I buy a blank one on Aliexpress, solder it and be good?

Board is FX 490 NM-B861, Rev 1.0.

Found the answer on another thread.

The ThinkEngine (BD4179MWV) does not need to be programmed when replaced

Just solder a blank IC and power it on, and wait a few minutes. The board will automatically reprogram it, just dont interrupt it out of impatience so it doesn't fail, corrupt and then refuse to program again.

Source: https://www.badcaps.net/forum/troubl...shooting/page2

I retract my statement. I ordered a replacement ThinkEngine from AliExpress from a well-rated seller.

I replaced it today and upon powering on the board, it's just power cycling extremely rapidly. My USB C Ameter doesn't even have a chance to boot up because of how rapidly it's cycling.

I presume from these symptoms that the issue is the lack of firmware, but the previous post said that it auto-programs. Of course, it's entirely possible that the IC itself is faulty or came with the wrong firmware.

Can anyoneh elp and confirm whether or not this requires external programming?

Hi [автор темы](https://www.badcaps.net/member/281081-автор темы)

Your post is from a while back, but I'd like to ask if you were able to resolve the issue back then?

Can you take a look at my post about a similar problem? Maybe you can share your experiences.

THX

​

The led that shows that pattern (i.e. 3 blinks) is the LED_PWR and it's controlled by the EC (page 85 of the schematic).

From post # 7 - you have ~20v onboard. If the power adapter is the USB Type C, this confirms that the TE is working since the power delivery contracts have been negotiated with the external USB C power adapter and the power rail has switched from the power on default of 5v to 20v. Can you confirm this detail? The communication is over the CCx pins. There is CC1 on one side of the USB C connector; CC2 pin will be on the other side of the USB C connector.

Turn off all power and unplug the USB C power adapter from the wall - personally do not trust them at all - then rotate the USB C plug to your laptop by 180 degrees. Now plug the power adapter to the AC socket. Do you see ~20v again? If yes, the PD controllers are working.

Yes, I can confirm that the PD negotiation seems to work properly. I tried with the USB-C connector in both positions (and disconnected the AC adapter from the wall as you suggested each time).

In both cases, on the board I can measure 19.8v on pin 45 (VREGIN20) of the TE.

To me, TE is working fine due to this 20v negotiation.

Carefully, measure the voltage to ground on each pin of the DCin mosfet that follows this power path to power the main power rail.

Test the voltage to ground on mosfet @ PQ0201.

Interested in:

**source (1-2-3) ; select any pin.

gate (4)

drain (5-6-7-8) ; select any pin.**

Post each measurement.

On my board, the PQ0201 is a Dual N-channel MOSFET:

Here are the measurements:

pin
measure

pin
measure

1
~400mV

5
0v

2
20v

6
0v

3
20v

7
0v

4
20v

8
5.8v

9
~308mV

Mhhhh... while I was looking at page 102 for the measurements, I noticed that the -EXTPWR signal is originated there, and it's actually low!

Based on the power sequence from the X270 documentation, -EXTPWR should be the next in line to go up (in the other schematic it's called -EXT_PWR_GATE, but I guess both refer to the same signal)

My bad...indeed a dual mosfet inside a single package.

However, in the schematic there are 2 part numbers used for this component. Each is a DUAL N-channel mosfet so this implies that the gate voltage must be higher than the voltage being passed betwee source / drain pins to enable.

On the BQ series, the N-channel driver pin should be ~25v and is based on adapter voltage + REGN voltage = 20v + 6v = ~25v to enable the mosfet.

Noting that we do not have this voltage from the BQ charger IC, proceed to test the following pins of interest.

Remove all power. Meter in resistance mode.

Measure the resistance across each mosfet pin:

**source / drain

source / gate

gate / drain**

of the 1st mosfet inside this package

then repeat for the 2nd mosfet inside this package.

We are checking if there is a low resistance which often means the mosfet is shorted and needs to be replaced. Each measurement should be hundreds of k ohms or higher if normal.

Assuming the resistance checks are ok, carefully review the voltage to ground of the following pins of interest on the charger IC:

**VBUS ; pin # 1

REGN ; pin # 28

ACN ; pin # 2

ACP ; pin # 3**

See attached for the datasheets for the dual mosfet parts used at this location by the PCBA shop:

Вложения: https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/3465716-thinkpad-t14s-gen-1-nm-c891-no-power-i-could-use-some-help-with-the-troubleshooting/filedata/fetch?id=3523485&d=1733595828

The Dual MOSFET on the board is marked 0924NDI, so it's the Infineon.

High side (gate:1 -- source:9 -- drain: 2,3,4) source / drain
150k and raising

source / gate
220k

gate / drain
450k and raising

Low side (gate: 8 -- source: 5,6,7 -- drain: 9) source / drain
87k

source / gate
210k

gate / drain
346k

On the IC charger I find: pin
name
measure

1
VBUS
20.12v

2
ACN
20.11v

3
ACP
20.12v

28
REGN
6v

The low side mosfet inside this dual mosfet looks to be quite low (87k ohms) for a good mosfet.

Suggest to flux and remove this dual mosfet and test the component while it is on your workbench. Are these measurements still this low on your bench? Each should be hundreds of k ohms or higher. This part may be defective.

Can you measure in the same manner the dual mosfet @ PQ0202? Post your measurements.

Your voltage measurements look good.

Here what the PQ0201 shows when off the board:

High side (gate:1 -- source:9 -- drain: 2,3,4) source / drain
4M

source / gate
OL

gate / drain
OL

Low side (gate: 8 -- source: 5,6,7 -- drain: 9) source / drain
123k

source / gate
OL

gate / drain
OL

And the PQ0202 (in circuit):

High side (gate:1 -- source:9 -- drain: 2,3,4) source / drain
160k and raising

source / gate
219k

gate / drain
229k

Low side (gate: 8 -- source: 5,6,7 -- drain: 9) source / drain
141k

source / gate
201k

gate / drain
340k

​

Both PQ0201 & PQ0202 look too low for me. Suggest to flux and replace both dual mosfets. Before you do this, measure the fresh ones while they are on your work table. You can use the measurements as a comparison of a known good mosfet. Each will be much higher in measurement. Recommendation is to source from tier 1 distributors like Digikey / Mouser / Arrow and only if you must, Aliexpress but select a vendor with very high ratings.

Many thanks for the suggestion. I'll give it a try.

As a matter of fact, I have another board from the same Lenovo generation but based on AMD Ryzen architecture. This part of the board is based on the same BQ charger IC. I'm tempted to take the dual mosfets from there What do you think?

I'd replace the Infineon 0924NDI with SM7360EKQG (more beefy), and the SiZ340DT with AONH36334 (a bit smaller in amps). The latter code is from the schematic, the package is actually marked "M6 VUA 2W0E08" on the board, but I couldn't find a datasheet using this identified. I'm attaching the datasheets for reference.

Attached Files
Premium supporters get full download access and other benefits.

•
SM7360EKQG.PDF

(331.5 KB, 77 views)

•
AONH36334.pdf

(729.6 KB, 3 views)

_Вложения: SM7360EKQG.PDF

							(331.5 KB, 77 views), AONH36334.pdf
							
								
							
							(729.6 KB, 3 views)_

I finally found some time and replaced the dual mosfets.

I replaced both PQ0201 and PQ0202 with their counterparts from a similar board I have (let's call it blue-pcb). The latter has other problems, but the power stage seems fine since it comes up, charges the battery and shows BIOS screen.

Unfortunately, I still get the 3 blinks on the power button white led. So no visible change in behavior.

The blue-pcb donor board keeps working the same way with the mosfets from the board I'm trying to repair.

Any other idea?

Recently, I had the same problem, and it was resolved by flashing the EC controller and selecting the correct BIOS.

​

Forgot about this thread. Are you still working on it? Do you get VSYS15 at all or is the main power rail dead? Have you checked it isn't shorted?

Originally posted by участник

Recently, I had the same problem, and it was resolved by flashing the EC controller and selecting the correct BIOS.

​

Hi there! Thanks for sharing. Honestly, I also considered trying that Provided that I'll be able to find a bin to flash for this board, is it something I could do with a ch341a?

Hi all, I'm thrilled to finally be able to close this thread! I managed to fix the issue and everything is working perfectly now.

A massive thank you to everyone who jumped in, offered suggestions, and helped me troubleshoot. This community is just incredible, and I genuinely appreciate the time you all took out to help me solving this puzzle.

In case someone else ends up here facing a similar problem, I want to leave a few additional observations. Hopefully, this saves someone else a bit of headache down the line!• The ThinkEngine (BD4179MWV) does not need to be programmed when replaced

• The white LED on the power button blinking three times when plugging the AC adapter in it turns out to be totally normal. I noticed it, by chance, on another T14s. This pushed me away from the solution for quite sometime, since it made be suspect issues with the MEC EC

• Once the previous point was cleared, I went back to my suspect that a misalignment between EC and BIOS could prevent the board to start correctly. Unfortunately, in my case, the person who previously tried to fix the board removed the BIOS chip and didn't bother putting it back on, so I was not able to find any clue about the original BIOS version. I tried a couple of BIOS dumps I found on this forum and on another community channel but without success. Eventually, the one shared on this post did the trick for me! (it's a N2YET35W v1.24)

After I fixed the board, I confirmed that the EC runs version 1.08, hence I needed a BIOS version >= 1.15

In fact, from [Levovo BIOS changelogs for this model](https://download.lenovo.com/pccbbs/mobiles/n2yur19w.html):

UEFI: 1.15 / ECP: 1.08

- (New) (Note) If the UEFI BIOS has been updated to version 1.15 or higher, it is no longer able to roll back to the version before 1.15.

- (Fix) Fixed an issue where wrong battery remaining percentage might be shown.

Man, it feels so good!

Where you buy good TC62D518FTG ? I buy from aliexpres 2 pieces and they dead,no volt,only 20v in..

Originally posted by участник

Where you buy good TC62D518FTG ? I buy from aliexpres 2 pieces and they dead,no volt,only 20v in..

Following the suggestions I found in the forum, I tried to find a seller with high number of reviews on Aliexpress. If I remember correctly, I bought both BD4179MWV and EEPROM from SUHMS

Good evening...

Please tell me.

How and with what did you load the 32M BIOS?

I read and loaded the RT809H, but it was 290 bytes in size.