Lenovo 300S-14isk notebook does not respond to maintenance after startup

Lenovo 300S-14isk notebook does not respond to maintenance after startup

Machine model: Lenovo 300S-14isk 

Board number: 14292-1

Malfunction: the battery and adapter cannot be used at the same time.

Maintenance process:

A Lenovo 300S-14isk notebook, the battery and adapter can’t be used at the same time, and the adapter works normally, but as long as the battery is plugged in, the system can’t be accessed, or the power indicator flashes, and the battery can be used alone.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 1.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 2.

At the same time, insert Short circuit, either the adapter side isolates MOSFET Short circuit or the battery isolates MOSFET Short circuit. Disassemble the machine and measure each MOSFET to be normal.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 3.

When the battery is plugged in, the machine can’t be charged. First, change the charging chip. The fault becomes auto power off at the moment when the adapter is turned on. When the power is turned on to 0.5, the fast auto power off is the same whether the memory is plugged in or not. Replace the original charging chip. The fault remains the same,auto power off is not displayed, and the BIOS is the same. However, when the battery is turned on, it can be displayed.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 4.

Measuring the working conditions of the charging chip, 24780, the first signal ACOK 0V, Wori disconnect node, and the problem of 0V lies in the charging chip.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 5.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 6.

Tracing ACIN requires the benchmark VCC partial pressure of 24780. After measuring and disconnecting the charging chip ACOK, it only needs 0.6V here, but it actually needs 3.3V.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 7.

Lenovo 300S-14isk notebook does not respond to startup repair Figure 8.

Tracing PWR_CHG_REGN benchmark VCC is only 1.18V, which is 6V normally.

Lenovo 300S-14isk notebook does not respond to startup repair Figure Figure 9.

Check the main VCC of 24780. According to the manual of 24780, the output of 24 pin REGN 6-V linear regulator is provided by VCC. The LDO is active when ACDET is higher than 0.6 v and VCC is higher than UVLO.

Connect a ceramic Capacitor device ≥2.2μF 0603 from REGN to GND, between REGN and BTST.diode; the one who lacks dialectical thinkingbeIntegration.

The actual measured 6 pin ACDET 2.67V is normal, and the main VCC 28 pin is only 2.49V The measured resistance of 28 pin is close to OverLoad.

Lenovo 300S-14isk notebook does not respond to startup repair Figure Figure 10.

Lenovo 300S-14isk notebook does not respond to startup repair Figure Figure 11.

After changing PR4413 to 10 ohms, the trouble is eliminated and all problems are solved.

Lenovo 300S-14isk notebook does not respond to startup repair Figure Figure 12.

PR4413 should be defective, which caused the initial battery and adapter not to be used at the same time. Later, when the 24780 was replaced, the resistor was heated, resulting in serious defects and adapter switch auto power off.