DELL Inspiron 15-7572 Laptop Not Turning On

 Machine model: DELL15-7572

Board number: LA-F251P 1.0

 

Repair Process:

The fault showed that the power-on current was 0.4, then dropped to standby current, and the problem remained the same after being triggered again. 

    When the board is turned on, the fan spins wildly, the current is stuck at 0.4, and the fault light does not flash or light up. I first refreshed the BIOS.But the sound remained the same, and the fault persisted even after replacing the memory. 

     I first tested the platform reset according to the timing. The PLTRST was 3.3V, and the BIOS was also flashed. Then I remembered that there was a DRAMRST#.

    I checked that the memory slot pins were welded well. I measured that the power supply was 1.2V, but the DRAMRST# was not. ,0.06V.

There is a 470 ohm resistor on the back of the wiring that pulls up from 1.2V. The resistance measured online is normal.

The resistance of the memory slot DRAMRST# pin to ground is normal and not short-circuited. One end of the resistor is 1.2V and the other end is 0.06V. If there is no short circuit, What was pulled down? The signal goes directly to the CPU.

Replaced it with a 470 resistor. I used my own memory and turned it on again. The current jumped unexpectedly. I measured again and found 1.19V at both ends of the resistor. I picked up the customer's 8G memory, installed it and turned it on, and the sound of waves was still the same.

One end of the resistor became 0.06V again, but this time the motherboard fault light started flashing, a few yellow lights, and a few white lights. To be on the safe side, I disassembled the machine again and replaced the resistor. I did not access the customer's memory again, so I took a new one.

The 4th generation 8G memory was installed and triggered, and the current was high. After testing for a while, it turned on and off again and everything was normal.

Happy Repairing !!