ASUS a540u laptop does not show repair after startup

Model: Asus A540U

Fault version number: X540UP

ASUS a540u laptop does not show repair after startup Figure 1.
Malfunction: The laptop didn’t show when it was turned on, and it didn’t move when it was powered on for 0.6. The customer said it was water damage, but it was no booting after cleaning.
Fault analysis: The current of 0.6A or so does not move, so it should be out of memory.

Maintenance process:

The bare board brought by the machine, the direct power-on test shows that 0.6A or so does not move. After measurement, 3V 5V 1.2V 1.35V 1.05V 0.85V 0.9V and 12V charged ones all come out, but the integrated display does not.

ASUS a540u laptop does not show repair after startup Figure 2.

If you suspect that you haven’t read the memory, find the point directly to see if you have read the memory, and go to the oscilloscope to catch the wave for detection.

ASUS a540u laptop does not show repair after startup Figure 3.
The bus position of the 4th generation memory is two pin bits, 253 and 254. The oscilloscope found that only VCC has no waveform, so we can directly see whether the memory conditions are met.

ASUS a540u laptop does not show repair after startup Figure 4.
28 pin VTT: 0.6V normal, 259 pin VPP1 VPP2:2.5V normal, 255 pin VCCSPD:3.3V normal, VDD:1.2V normal.

ASUS a540u laptop does not show repair after startup Figure 5.

08 pin Resrt: 1.2V normal, 134 pin EVENT:1.2V normal, 164 pin VREFCA:0.6V normal.

Basically, the conclusion can be drawn from the maintenance here. There are many factors causing code failure, the most common of which is the code failure caused by BIOS. Find a factory directly to write the BIOS test, power on and measure 253 and 254 pin again. It is found that the wave has been read, the screen test has been booting up, and the maintenance is finished.

ASUS a540u laptop does not show repair after startup Figure 6.