Asus U4000U notebook no booting repair

Machine model: ASUS U4000U

Board number: UX310UV 2.0

Malfunction: Notebook no power on

Maintenance process:

An ASUS U4000U laptop can’t be turned on. Plug in EC AVCC VCC+3VA_EC in constant high and low current of change, and EC _ rst # is also constant VCC 21201, and use analog oscilloscope to see the waveform.

Asus U4000U notebook no booting repair figure 1.

Check that the source of +3VA_EC is converted from PU8801.

Asus U4000U notebook no booting repair figure 2.

EN1 PS_ON of PU8801 turns on +3VA to +3VA_EC,PS_ON is issued by EC, and PS_ON VCC is also issued by current of change, which seems to be a PS_ON problem.

Asus U4000U notebook no booting repair figure 3.

The waveform of PS_ON_EC VCC is also current of change. Check the conditions for EC to issue PS_ON_EC.

The reset of EC and AVCC can only be generated when there is +3VA_EC. Check the signal pulled up by +3VA, and the following are EC pulled up by +3VA or VCC:

Asus U4000U notebook no booting repair figure 4.

The VSTBY0 VCC is normal, PWR_SW# and LID_SW# have a high level of 3V, and AC_IN_OC# has a low level of 0V.

Under normal circumstances, after the EC gets the VSTB0 deep sleep VCC, when the battery is plugged in, the normal PWR_SW# that needs to get the high level LID_SW# and current of change will send out the high level PS_ON_EC, and when the battery is not plugged in, the AC_IN_OC# normal low level and LID high level EC will automatically send out the PS_ON_EC, without plugging in.

+3VA Diode value is normal VCC is also normal, which is suspected to be caused by EC damage. Replace EC directly.

Asus U4000U notebook no booting repair figure 5.

After the replacement, it will be automatically powered on.auto power off will be booting up at one time. The installation test is OK and it is perfectly repaired.