Lenovo Xinchao 7000-13 notebook no power on maintenance

Lenovo Xinchao 7000-13 notebook no power on, found the fault point c6705 to the CPU chip VCC pin filter Capacitor Short circuit.After replacement, the common point diode value becomes more than 400 ohm, and the laptop can be turned on normally after power up.

Machine model: Lenovo xiaoxinchao 7000-13

Main board No.: 1701a_05_01 REV:MP

Fault phenomenon: Lenovo xiaoxinchao 7000-13 notebook no power on 、

Maintenance process:
When the power supply is not over the common terminal, the resistance of the common terminal is measured to be 0 ohm.It indicates that Short circuit caused Current protection.After measuring each large Inductor and disconnecting each test point, no Short circuit can be found, so we have to use the Current heating test method. If this motherboard is burned, it is difficult to find hot spots. You can only add large current to burn for a while, and slowly feel it with your hands.

The result shows that the fault point c6705 gives the VCC pin of the CPU chip VCC to filter Capacitor Short circuit.After replacement, the common point diode value became more than 400 ohm. After power up, the laptop can start normally, but it is found that the battery cannot be charged.Both the battery and the adapter can be turned on, the battery can be found, but it cannot be charged.

The charge and discharge circuit isl95521 was tested. Under the condition of external Connect the power supply source adapter, it was found that Pin1 AcIn 2.1V was normal (pin potential was 0V without adapter), but Pin2 pin ac0k power supply was 0V (the pin point should be 3.2V or so when connected with adapter) and external r5914 was detected. One end of the resistance was connected with + v3p33a_EC (3.3V), the other end is connected with isl92221 Pin2 acok terminal.It is found that the resistance has been increased to more than 10 megabytes. After replacement, the charging fault has been eliminated and the machine has been repaired.

Lenovo Xinchao 7000-13 notebook no power on maintenance Figure 1