Dell 2420(10315-1) Not Charging. Even After Changing The Battery Repair

Laptop Model: Dell 2420  

Board number: 10315-1

Fault: Not Charging. Even After Changing The Battery.

 

Measured Fault:

 

The battery installed in the machine of the same model cannot be recognized (battery is bad), the single power supply motherboard can be turned on normally, and a good battery of the same model is installed at the same time when the power is plugged in.

Sometimes it can be turned on and charged and sometimes it is protected (the motherboard is bad).

 

Repair Process:

Plug in the protection at the same time, first check the protection isolation module: the three isolation tubes are all good, the charging chip meets all conditions and has output level AC_IN#, indicating that the chip is OK, but the charging chip was replaced with 24737 The fault remains.

It was found that the single-battery mode could not be turned on, and the test again found that there was no standby. The linear test again successfully output no PWM start signal.

The final turn-on signal S5_ENABLE was sent by EC. The test again showed no EC standby voltage. The EC standby came from the linear conversion and was finally controlled by Q2703.

At KBC_ON#. KBC_ON# is controlled by any one of the switching signals KBC_PWRBTN# and AC_IN#, as illustrated below.

This is an energy-saving circuit. When the adapter is inserted into this circuit, it is controlled by AC_IN# to generate EC standby.

EC works normally and the output standby is turned on. When a single battery is inserted, press the switch to generate standby, and this signal is continuously pulled low by EC.

After studying the triggering of the above circuit, EC standby came out, and PWM turned on, but there was still no output. I checked the waveform and found that both 3 and 5V were active, but none of the outputs were normal.

Then I plugged in the adapter and found that the motherboard It is in the protection state. This kind of weird fault can be easily replaced with a 51125, and the battery mode can be successfully turned on.

It shows that the motherboard protection is caused by the abnormal output of the standby chip, but it is not abnormal every time. The battery mode is more frequent, so the battery circuit is used to repair the machine. The light-up diagram is attached.

Happy Repairing !!