Lenovo ThinkPad X1 Yoga notebook computer maintenance without charging

Lenovo ThinkPad X1 Yoga laptop doesn’t charge. It is found that ACDET has a maximum of 7V, and the measured voltage is greater than this voltage. The charging IC must be dead. Power-on test, charging everything is normal, and it will be charged to ninety-seven percent soon, and the repair is completed.

Model: Lenovo ThinkPad X1 Yoga laptop

Main board number: 14282-2M

Malfunction: The laptop does not charge.

Maintenance process:

A Lenovo ThinkPad X1 Yoga notebook computer, the fault is isolation protection.

Lenovo ThinkPad X1 Yoga notebook computer does not charge maintenance Figure 1

Dismantling found that BQ24780S charging chip burned, many insurances were broken, and two 20-ohm insurance resistors were also broken. Change a charging chip and connect all the broken insurance. The adapter can be turned on, and it can be turned on with batteries, but the computer is not charged. After the charger is unplugged, it still shows that the adapter is plugged in.

Check the working conditions of the charging chip first. Some drawings of the charging chip are as follows:

Lenovo ThinkPad X1 Yoga laptop is not charged for maintenance Figure 2

There is an output of adapter status here. After measurement, it is 3.3V whether the adapter is plugged in or not. This is obviously a problem. According to the manual of this chip.

Lenovo ThinkPad X1 Yoga laptop is not charged for maintenance Figure 3

When ACDET is greater than 2.4V, ACOK is at a high level, that is, 3.3V On the contrary, if ACDET is less than 2.4V, ACOK is at a low level, that is, 0V.

Then measure ACDET, which is 11.3V when there is no adapter connected, and up to 15.4V after the adapter is connected.

Lenovo ThinkPad X1 Yoga notebook computer without charging maintenance Figure 4

The voltage of ACDET is divided by the common point voltage by these two resistors. Measure these two resistances. when R7117(66.5KΩ) is measured, the resistance value exceeds 10MΩ ω. After washing and soaking with washing water, a corner was found to be broken.

Lenovo ThinkPad X1 Yoga notebook computer does not charge maintenance Figure 5

It’s a resistor in 0201 package, and its volume is very small. I found a bunch of resistors to make this ratio.

Lenovo ThinkPad X1 Yoga laptop is not charged for maintenance Figure 6

Power-on test, the voltage is normal, 1.7V adapter is not plugged in, 2.6V adapter is plugged in, but ACOK signal is still 3.3V Check the charging chip manual.