Samsung NP-R428 notebook does not trigger repair

Samsung NP-R428 notebook does not trigger repair

After removing D516, the standby chip is no longer hot. Short circuit was found in the third pin of D516, which was only 30 to the ground. The circuit diagram shows that P3.3V_MICOM connects two resistors and three capacitors. Troubleshooting after removing the capacitor.

Machine model: Samsung NP-R428

Main board number: BA41-01215A

Fault symptom: the notebook does not trigger.

Maintenance process:

This notebook is equipped with Pentium T430 CPU, but fortunately it is DDR3, and there are drawings and no points. Get the machine, plug in the adjustable power supply first, the standby current is more than 180 mA, the value is on the high side, and the notebook triggers without response.

Samsung NP-R428 notebook does not trigger maintenance Figure 1

Disassemble and test the common point. The voltage is 19V, and there is no 3V and 5V. Later, I learned that this machine will not generate 3V and 5V voltage until it is triggered. The hand-touched standby chip RT8205AGQW was very hot. Due to lack of experience, it was changed to a RT8205C without measurement. As a result, the fault remains the same.

Measurement P5.0V_STB is normal, measurement P3.3V_MICOM is 1.8V abnormal, and measurement P3.3V_MICOM is not short-circuited. The burning machine solution did not burn out. P3.3V_MICOM is measured again, and the result is normal, with a value of 3.3v.. The notebook can be triggered.

Thought it was fixed, but it didn’t work. The current is 500MA, and the basic voltage is all available. Touching the standby chip RT8205AGQW again is still very hot. It seems that it is impossible to fix it here. I guess there must be a short circuit in the back stage.

Open Xinzhizao and check where the drawing P3.3V_MICOM went. Knowing that the first place to go is RTC circuit.

Samsung NP-R428 notebook does not trigger maintenance Figure 2

Samsung NP-R428 notebook does not trigger maintenance Figure 3

After removing D516, the standby chip is no longer hot. Short circuit was found in the third pin of D516, which was only 30 to the ground. The circuit diagram shows that P3.3V_MICOM connects two resistors and three capacitors. Two capacitors were found nearby, but they were still the same after being removed. Because there is no point bitmap, I can only look everywhere, and finally I found it under the black tape on the back of the motherboard. After removing the capacitor, I removed the fault.

Samsung NP-R428 notebook does not trigger maintenance Figure 4

Summary: The short circuit of C145 caused the linear 3V to be pulled down, which led to the notebook not turning on. COMS battery has also been discharged. Can only be replaced.