Looking to learn about troubleshooting my Lenovo L14 Gen 1

[Lifeisfun]

That is toasty. Chip was replaced? Was the chip soldered in the proper orientation on the board?

Thanks for reply!
I did not replace the BQ chip, only the EC chip and I'm pretty sure I did orient it correctly and did not overheat it.

[Lifeisfun]

It's NVDC design (Narrow VDC), see https://www.badcaps.net/forum/troubl...arging-circuit
I agree with mon2, the BQ25700A is too hot, it's available at mouser if its determined to be faulty

So the main power rail and battery charge voltage is dependant on the battery configuration, so for 3S battery the fully charged voltage should be from 12.6v - 13v, similar as the Macbook charge circuit with the ISL chips
With battery unplugged you should get 12.6 or 13v
Could be the main rail (VSYS15) is unstable?, that may be the cause

Without the battery connected there is only 9.4V or so, must be something wrong then.
Will check the VSYS15

Does the BQ chip only handle the battery charging and battery to USB-C switching? If so, can I remove it and try to power on without it?

Thanks

[m1ch43lzm]

tt won't work, as the BQ generates the main power rail, and charge the battery at the same time
If working on battery only, the BQ connects the battery (BAT_PWR15) to the main power rail (VSYS15) by turning on PQ0201
So it's an essential component on the board

Do you still get the proper voltages at the 3.3v regulator?

[Lifeisfun]

tt won't work, as the BQ generates the main power rail, and charge the battery at the same time
If working on battery only, the BQ connects the battery (BAT_PWR15) to the main power rail (VSYS15) by turning on PQ0201
So it's an essential component on the board

Do you still get the proper voltages at the 3.3v regulator?

Oh, OK, thanks for the explanation, yes, the 3,3V rail is fine.
Will swap the BQ chip and report back

THANK YOU!

[Lifeisfun]

Another question, any reason for the BQ chip to be 49C when the battery is not even connected? The mosfets around tested OK and not shorted.
When I connect the battery (12.6V charged to 11.35V) the charging voltage is only 12.4V not 15V and it's slowly dropping not going up.
Could this be possible reason for the board not to post?

Thanks

I have another question about the VSYS15 voltage.
Considering I get on the VSYS15 only 9.4V without battery connected and 12.4 with battery connected, is there any way to test if something is causing this drop?
Can I inject voltage on the VSYS15 rail and see if anything is getting hot? If so what would be safe Voltage and Amp limit?
The PR0201 coil is warm without battery and very hot with battery connected.

Thanks

UPDATE: Just tested VSYS15 resistance to ground and its about 5M+ so I presume there is no problem there.

[m1ch43lzm]

The PR0201 coil is warm without battery and very hot with battery connected.

Do you mean PL0201? (at the other side of the BQ, on the top side of the board) Measure resistance to GND, that coil shouldn't get hot at all, it's part of the input to the charge circuit

You should have 20v there with the charger plugged in, and nothing (0v) with only the battery connected (charger unplugged)
Check with thermal cam what else gets hot, could be a cap, the BQ itself, anything

Something is really wrong in that area to make a coil get hot

Or PR0201, the current sense resistor? (near the M.2 connector) Same, it shouldn't get hot at all

[Lifeisfun]

Do you mean PL0201? (at the other side of the BQ, on the top side of the board) Measure resistance to GND, that coil shouldn't get hot at all, it's part of the input to the charge circuit

You should have 20v there with the charger plugged in, and nothing (0v) with only the battery connected (charger unplugged)
Check with thermal cam what else gets hot, could be a cap, the BQ itself, anything

Something is really wrong in that area to make a coil get hot

Or PR0201, the current sense resistor? (near the M.2 connector) Same, it shouldn't get hot at all

Sorry, that was oversight on my part ( assumed and I was wrong)
It is actually very strange, since even the board view doesn't ID that coil or the larger mosfet to the left above it.

The PL0201 is not present and the jumper is in place (jumper is 49K to ground) Yes there is 20V on that jumper and 20V on pin 1 of the BQ chip.

PL0202 (I assume since is not marked anywhere) is the one getting hot when battery is connected and warm without battery. (1K to ground on that coil)
The BQ chip is slightly above it on the other side of the board (BQ chip is definitely hot 50C or so)


Once again sorry for the wrong info before.

Thanks!

[m1ch43lzm]

Get the board view from post #19 https://www.badcaps.net/forum/troubl...16#post3231416

You can open it with flexbv free
https://www.badcaps.net/forum/troubl...acos-and-linux

That will help identify those components

Anyway, from the resistance measurements, likely PU0201 is faulty (BQ25700A), according to schematics there shouldn't be a way to get 1k resistance to GND at PL0202 unless either PQ0204 and/or PQ0205 are faulty, or the BQ itself is faulty

Now remove the BQ and check resistance to GND at PL0202, you should get OL

Don't apply power to the board unless you replace the BQ

The charge circuit while in operation shouldn't get hot at all, at most around 30-35 deg C, I checked on my laptop (HP), while the charger IC is an ISL the topology is similar NVDC, i couldn't feel anything hot with my fingers while charging the battery (I don't have a thermal camera)

[Lifeisfun]

Get the board view from post #19 https://www.badcaps.net/forum/troubl...16#post3231416

You can open it with flexbv free
https://www.badcaps.net/forum/troubl...acos-and-linux

That will help identify those components

Anyway, from the resistance measurements, likely PU0201 is faulty (BQ25700A), according to schematics there shouldn't be a way to get 1k resistance to GND at PL0202 unless either PQ0204 and/or PQ0205 are faulty, or the BQ itself is faulty

Now remove the BQ and check resistance to GND at PL0202, you should get OL

Don't apply power to the board unless you replace the BQ

The charge circuit while in operation shouldn't get hot at all, at most around 30-35 deg C, I checked on my laptop (HP), while the charger IC is an ISL the topology is similar NVDC, i couldn't feel anything hot with my fingers while charging the battery (I don't have a thermal camera)

You are great with all the hints and advice!
Thanks, will do!

[Sephir0th]

When the battery gets charged, the buck converter in NVDC designs can indeed get pretty "hot" till some extent. I won't agree with saying it is defective only from this observation. It's a common misunderstanding to think there is supposed to be 15V present just because there is "VSYS15" written. This is not true in any case. I can tell you that the engineers are just too lazy to change the rail designation...

In the end only the battery (nominal) voltage tells you how much voltage to expect on this raim

Also if with missing +VCCGFXCORE the internal graphics of the CPU is meant, it is absolutely normal for it not being present. This is not a issue per default. It will only come upnunder graphical load, at earliest in a Operating System environment.

From my understanding it's the point to check for picture/CapsLock response instead, before doing anything else.

[Lifeisfun]

When the battery gets charged, the buck converter in NVDC designs can indeed get pretty "hot" till some extent. I won't agree with saying it is defective only from this observation. It's a common misunderstanding to think there is supposed to be 15V present just because there is "VSYS15" written. This is not true in any case. I can tell you that the engineers are just too lazy to change the rail designation...

In the end only the battery (nominal) voltage tells you how much voltage to expect on this rail

Also if with missing +VCCGFXCORE the internal graphics of the CPU is meant, it is absolutely normal for it not being present. This is not a issue per default. It will only come upnunder graphical load, at earliest in a Operating System environment.

From my understanding it's the point to check for picture/Caps Lock response instead, before doing anything else.

Thank you very much for your time to respond!
There is something strange with the charging since the battery voltage is 11.35V but charging voltage is stuck on 12.4V and dropping.
Yes the coil is very hot when battery is connected but also warm without the battery when the voltage drops to the 9V range.
The BQ chip is also hot all the time.
There is no Caps LED lit and no response pressing the caps button (there is 3.3V on the keyboard)

I was all excited since I found YT video where someone is measuring resistance and voltages on this board but my happiness was short lived since the vide o is showing only last 3 digits of the multimeter
https://youtu.be/5gXg5LrUHjo?si=GX3GSHubjApvvMd_

[Sephir0th]

No, I am talking about the "Nominal voltage" of the battery, which is 11.1V when asking google.

For a LiPo battery with 3 cells in series (3S), nominally 11.1V, the full charging voltage is 12.6V. This is because each LiPo cell should be charged to 4.2V, and 4.2V * 3 = 12.6V.

So everything in specs here.

Also, when the board is full on up to even VCORE, then the charging controller can't be part of the issue. Seriously, it can't be. You can proof by testing with the main battery instead of the charger, this will most likely confirm that.

I'm sorry to tell that there is most likely a different issue way later in the power up sequence. With some luck it's "just" a BIOS issue. But unfortunately I fear something worse going on after the history. I suggest to start over with the troubleshooting, based on the current behaviour of the system. As much infos as possible and of course you can and you should simply share the values you wanted to compare with the video.

It could also be the case that the board is simply not charging the battery for whatever reason. But this has nothing to do with the power up, which the board does like you described, but a secondary issue which needs to be troubleshooted separately. The truth is that I did not understand im full what you explaining here and where you measured what. Thus is what it makes hard to respond something meaningful in this matter.

So questions here are:

Does it work from battery only?
Does it work from charger only?
dies the battery draw current when the board is NOT turned on?
Things like that, to at least roughly determine what is really going on in this section.

[Lifeisfun]

No, I am talking about the "Nominal voltage" of the battery, which is 11.1V when asking google.

For a LiPo battery with 3 cells in series (3S), nominally 11.1V, the full charging voltage is 12.6V. This is because each LiPo cell should be charged to 4.2V, and 4.2V * 3 = 12.6V.

So everything in specs here.

Also, when the board is full on up to even VCORE, then the charging controller can't be part of the issue. Seriously, it can't be. You can proof by testing with the main battery instead of the charger, this will most likely confirm that.

I'm sorry to tell that there is most likely a different issue way later in the power up sequence. With some luck it's "just" a BIOS issue. But unfortunately I fear something worse going on after the history. I suggest to start over with the troubleshooting, based on the current behaviour of the system. As much infos as possible and of course you can and you should simply share the values you wanted to compare with the video.

It could also be the case that the board is simply not charging the battery for whatever reason. But this has nothing to do with the power up, which the board does like you described, but a secondary issue which needs to be troubleshooted separately.

Yes, you are correct the battery spec is NOM 11.1 / 4.08Ah
Just tried again and it will not power on with only battery connected, I have to have the USB-C power connected (it ramps up on connecting power to 20V and about 0.48A)
Tested again and now with battery connected the PL0202 coil has 9V with battery connected or disconnected.
CPU is warm
Only power button response is holding it for 10 seconds or so, on first attempt it will reboot and doing it second time it wit shut off but the board is still taking about 40mA.

I will start all over again.
Is there any risk to have it powered on for long time when measuring? Also should I measure with or without battery connected?

Thanks

Board resistance and voltages
PL0701 2.5V 6Kohm
PL0601 1.19V 71ohm
PL0301 5.12V 400Kohm
PL0501 3.37V 151ohm
PL1003 0V 8ohm
PL0906/0903 0.96V 5.5ohm
PL1102 1V 25ohm
PL1403 1.05V 60ohm
PL0202 8.6V 61Kohm

[Sephir0th]

So it is most likely like assumed. A additional issue in the charging circuit. Battery could be simply locked in worst case.

But also 151 Ohms at the 3VALW, which is per 99% a partial short circuit of this rail. Something is faulty on this rail and we need to find out what it is. A almost impossible job without a thermal camera available.

[Lifeisfun]

So it is most likely like assumed. A additional issue in the charging circuit. Battery could be simply locked in worst case.

But also 151 Ohms at the 3VALW, which is per 99% a partial short circuit of this rail. Something is faulty on this rail and we need to find out what it is. A almost impossible job without a thermal camera available.

Thank you for the assessment!
I do have thermal cam, will look in to it!
Thanks!

EDIT
Interesting, this is the original problematic power supply where the LDO voltage to the EC chip was shorted, after replacement no longer shorted but perhaps some other issue

[Lifeisfun]

So it is most likely like assumed. A additional issue in the charging circuit. Battery could be simply locked in worst case.

But also 151 Ohms at the 3VALW, which is per 99% a partial short circuit of this rail. Something is faulty on this rail and we need to find out what it is. A almost impossible job without a thermal camera available.

The only hot thing glowing is the BQ chip at 59C all other smaller chips are under 30C, and the EC chip has no longer hot spot on it but it's evenly distributed 28C.

The replacement BQ chip should be here any day, I'll try to swap it to see if it will run cool.

Once again thanks for your time and knowledge!

[Lifeisfun]

So it is most likely like assumed. A additional issue in the charging circuit. Battery could be simply locked in worst case.

But also 151 Ohms at the 3VALW, which is per 99% a partial short circuit of this rail. Something is faulty on this rail and we need to find out what it is. A almost impossible job without a thermal camera available.

I did unsolder the PJ0502 jumper to separate the rail from the power supply, and yes the partial short is there.
What would be safe voltage and amperage to inject to find the problematic component?
This rail feeds lots of stuff incl. the PCH, I just hope the PCH is not partially shorted, that would be the end

Thanks

[Sephir0th]

I did unsolder the PJ0502 jumper to separate the rail from the power supply, and yes the partial short is there.
What would be safe voltage and amperage to inject to find the problematic component?
This rail feeds lots of stuff incl. the PCH, I just hope the PCH is not partially shorted, that would be the end

Thanks

This is what I would fear the most too...

The track will with 150 Ohms not draw much current anyway. So no need to set it up higher than 1 Ampere. Regarding the voltage you probably need to move directly to 3 Volts. Less would most likely don't reveal anything. More will harm what is still healthy on this rail.

[Lifeisfun]

This is what I would fear the most too...

The track will with 150 Ohms not draw much current anyway. So no need to set it up higher than 1 Ampere. Regarding the voltage you probably need to move directly to 3 Volts. Less would most likely don't reveal anything. More will harm what is still healthy on this rail.

Thank you!
Will give it a shot today and report back

[Lifeisfun]

This is what I would fear the most too...

The track will with 150 Ohms not draw much current anyway. So no need to set it up higher than 1 Ampere. Regarding the voltage you probably need to move directly to 3 Volts. Less would most likely don't reveal anything. More will harm what is still healthy on this rail.

Here are the results, I'm afraid it ain't good unless I see it wrong.
@3V the rail takes 120mA, and the only thing that I see slightly glowing is the PCH (pics before and after injecting voltage)
Makes me wonder what caused the damage, the EC chip was bad for sure since it was shoring the LDO 3V rail but why did it take out the PCH as well is beyond me.