Re: Lenovo Thinkpad T480 no charging
OK "fixed" it.
In case it happens to someone else..
I went off looking at the 20v lines since they were not working but the comms chips seemed OK in general.
Had to inject voltage and use iso alcohol to see it evaporating much faster.
It was a cap from the 20v line to ground that was almost 0 ohms resistance.
This showed up as the 20v input from charging circuit "VINT20_IN" towards the main power section showing as almost no resistance to ground.
Picture attached.
Both...
jamesportman
Member
Last Activity: 03-26-2023, 04:15 PM
Joined: 09-20-2022
Location: manchester
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Last edited by jamesportman; 09-22-2022, 08:05 AM. -
Re: Lenovo Thinkpad T480 no charging
OK think I have found an actual issue now, the 998CE chip above was a red herring.
Now I see that VCC for U198 is at 0.6v rather than 3v - pin 13, ts3ds10224 chip.
Checking the resistance from VCC3M to ground is about 180 ohms which seems very low.
Is there a way to narrow down without randomly removing components?
I tried to check resistance and voltage across caps nearby but I guess it doesn't measure them individually, it just shows the same for everything.
I suppose this is when heat/IR cameras...Leave a comment:
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Re: Lenovo Thinkpad T480 no charging
Ah thanks, my board is already set up like the workaround in that case.
So originally they might have installed the mosfet without the 0-ohm, then had issues with it burning out? So now the workaround fix as a revision?Leave a comment:
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Re: Lenovo Thinkpad T480 no charging
Maybe a sidetrack but I found the attached in motherboard schematics, "Workaround for PD burn-out issue".
The 0 ohm resistor is already there on my board but the mosfet is not.
I'm not sure what installing the mosfet would achieve, it is already bridged with the 0 ohm resistor, and that is still there in the workaround.
If the mosfet turns on is it just going to connect the same things that the 0 ohm resistor already is?...Leave a comment:
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Re: TPS65988CE specific datasheet/pinout
Yeah, I think the ~988DH might be what the "normal" datasheet from TI shows which is a different pinoutLeave a comment:
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Re: TPS65988CE specific datasheet/pinout
Thanks for the link.
Sorry this can maybe be deleted, I did find a motherboard schematic for my own board which has partial pinout for the CE chip at least....Leave a comment:
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TPS65988CE specific datasheet/pinout
Hi,
Does anyone has a datasheet specifically for TPS65988CE that would be great.
I have TPS65988 datasheet which is for a different pinout and is not useful.
ThanksLast edited by jamesportman; 09-22-2022, 02:57 AM. -
Re: Lenovo Thinkpad T480 no charging
Ah thanks for clarification, it's strange that the datasheet shows presumably the DH pinout but no mention of CE, can't find datasheet for it anywhere.
I'll ask for schematics in the requests area..
Edit: actually I do have the right mobo schematics already, will work from thatLast edited by jamesportman; 09-22-2022, 02:58 AM.Leave a comment:
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Re: Lenovo Thinkpad T480 no charging
Sorry yes that pin 51 and pin 20 are the ones I meant in first post that seem wrong.
And yes I went for the pin 51 you marked. You can see I marked above it by probing.
One of those two pins is 70k to ground, one is 130k to ground.
I think we both have the wrong datasheet or the datasheet pinout is a bottom view, or the chip is installed flipped horizontally?
If you look at what would be pin 23 and pin 48, they are both 100% grounds, 0 ohms.
There are even a few caps using the trace/areas as their ground side....Leave a comment:
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Re: Lenovo Thinkpad T480 no charging
You have me doubting myself now but top view being - a component installed onto the board, looking down on top of it?
I am definitely looking at the same datasheet, and assume the central pads are under the chip.
Dot in the corner for pin 1, also makes sense being bottom-left of the text on the chip, then anti-clockwise around it.
It looks like they've tried to make it clear by marking partial pin numbers but they are actually for a 48-pin chip?
Picture attached.
However, I see the two pairs of caps...Leave a comment:
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Re: Lenovo Thinkpad T480 no charging
Checking further into the tps65988 chip,
Pin 51 which should be ground is showing floating voltage of up to 30mv between it and a normal ground elsewhere on the board.
The other ground pin on the TPS chip is showing 0 mv.
Would that mean something is dumping/shorted to ground near pin 51? Or that chip is damaged?Leave a comment:
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Re: Lenovo Thinkpad T480 no charging
Thanks,
I did see one of those next to each of the ports, just marked 8S30 but I guessed they would be TPD8S300 like you say.
I checked the FLT (fault) pins of both of those chips with power cable connected and they are both still high at 3v due to pull up resistors. Apparently if faulty these pins are pulled low.
They both seem to be passing through whatever is on the four input pins to the output pins.
There is approx 1.7v and 0.1v on the CC pins depending which way around the cable is plugged in, nothing...Last edited by jamesportman; 09-21-2022, 03:01 PM.Leave a comment:
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Lenovo Thinkpad T480 no charging
Hi,
Short version: laptop works normally but won't accept charge from AC adaptors.
Longer version:
Lenovo Thinkpad T480.
USB-C/thunderbolt style charging port, you can use the main "power" connector or the thunderbolt port next to it to power the laptop normally.
Motherboard is NM-B50
Laptop was working fine, left switched off but charging.
Came back to it and the internal and additional batteries were dead.
No longer charges on either of the ports.
Got the laptop to boot by...Last edited by jamesportman; 09-21-2022, 01:16 PM. -
Re: New Members - please post your introductions here
Hello,
First post as per the PM since I am a new account.
I will start a new thread when allowed but having issues with my laptop not charging, spent some time already talking to the batteries outside of the laptop by using i2c and pretending to be a host, tried several chargers etc, so looking towards problems with the motherboard next.
CheersLeave a comment:
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