Lenovo Y400 notebook did not respond to repair when it was turned on

Lenovo Y400 notebook did not respond to repair when it was turned on

Machine model: Lenovo Y400 notebook

Main board version number: NM-A141 REV1.0

Malfunction: The notebook does not respond when it is turned on.

Maintenance process:

I received a Lenovo Y400 notebook computer. The failure described that the computer could be turned on before, sometimes no power on, and this time it was no booting directly. The power-on current of no power on is 0.03 or so.

Dismantling the machine, the bare board current bounces back and forth at 0.15-0.2 or so, but no response is found when pressing Switch. No obvious Short circuit was found in the power outage common point and major Inductor.

The measuring common point VCC 19.8V is normal, the measuring Current protection isolated upper and lower tube G pole VCC has 7 V VCC normal, and the 3,5 V standby VCC is also normal.

Measure the working conditions of EC IT8580e, measure the EC’s 74 pin+3valw _ ec VCC 3.3v normal, 18 pin+3valw _ r VCC 3.3vnormal, and measure 73 pin lid _ SW #VCC 3.3vnormal. 120 pin ACIN VCC Only 2.6 V VCC is abnormal.

Lenovo Y400 notebook did not respond to repair when it was turned on Figure 1.

Aci VCC is divided by PR297 and PR299, pulled up by PR298 and controlled by PQ45b. The measured BQ24737 _ VD VCC V is normal, the G pole ACPRN 0 V of PQ45b is normal, and the divided voltage produces Pacin3.3V.

The pull-up is normal, only 2.6 V is passed through the resistor PR298 to EC, and there is only one Capacitor in the middle. When Capacitor is disassembled,VCC remains the same. There is no disconnection when measuring EC to PR298, and there is no problem when measuring Switch VCC. Remove EC directly. Measurement ACIN VCC is normal.

Lenovo Y400 notebook did not respond to repair when it was turned on Figure 2.

Replace EC, the current jumps back and forth between 0.08 and 0.20 or so, and measure ACIN or 2.6V

Lenovo Y400 notebook did not respond to repair when it was turned on Figure 3.

The EC was removed again, and the measured ACIN was 3.3 V again.

Lenovo Y400 notebook did not respond to repair when it was turned on Figure 4.

I put the original EC back, and replaced the isolation chip, standby chip, standby 3,5 V filter Capacitor, standby linear VCC filter Capacitor, and the BIOS was also brushed, still the same. .

VCC, which is on standby again, and linear VCC of 3,5 V are normal and stable.

Lenovo Y400 notebook did not respond to repair when it was turned on Figure 5.

When measuring the standby 5 V, a slight jump was found. The upper and lower tubes of 5 V were replaced, and the measured ACIN was 3.27 V.switch: When the current goes up for a while,auto power off, brush back to the original BIOS, and turn on Boot.