11-08-2019 01:24 PM
I have a Lenovo T460s that will only charge when the computer is either turned off or in hibernation.
When turned on, I get the dialog box stating that "Incorrect AC adapter is attached." , along with the boilerplate text that details the problem, and gives some helpful advice.
I have searched the forums for a solution, and have tried a few things (like disabling airplane charging mode) but to no avail.
We had replaced the power cord and charger, but the problem persists. I suspect that the charging port itself was damaged, and not the charger.
Is it possible to determine if the problem is truly due to a lack of amperage (or wattage)?
I suspect that the rectangular charge adapter has a simple detection mechanism to determine the wattage of the power supply, and that this mechanism is causing the laptop to incorrectly detect the wrong type of power supply.
If this is the case, is there a setting, either in BIOS or in Windows itself, that can disable this detection and enable the laptop to charge, despite the damaged port? (I realize this is not ideal or recommended.)
Thanks in advance.
11-08-2019 02:20 PM
The determination is based on the resistance between the signal pin (in the center) and the outside face of the plug.
11-08-2019 02:32 PM
The resistance between the center (sense) pin and the ground is how the laptop determines if the proper power adapter is installed; the other two connections being the the negative and positive for the 20V DC supply.
The difference between the 65W, 90W and 135W power supplies is just the output amperage they can supply (higher amp models can handle more load, and charge faster), but the output voltages tested between the positive and negative terminals of the rectangular (slim tip) jack will be 20V DC on all of them.
This chart is for the 65W and 90W, but the 135W is similar, except I believe the resistance between its center pin and ground is 995 Ω.
If the adapter pug checks out OK it could be something internally with the DC Jack itself, which thankfully on that model is cheap and fairly easy to swap out since you only need to remove the base cover to remove/replace.
00JT985 Lenovo Ct Cables Internal (DC-IN)
ThinkPad T460s Hardware Maintenance Manual (see page 86)
Note: Be sure to read and follow the instructions on how to disable the internal battery and removing the base cover etc. that begin on page page 67 of the Hardware Maintenance Manual.
Help videos from https://support.lenovo.com/us/en/solutions/HT505031
Remove Base Cover
Installing DC in connector (shown with system board removed, but gives you somewhat of an idea)