Lenovo 40-70 ultra thin notebook no power on no booting maintenance

Lenovo 40-70 ultra thin notebook no power on no booting maintenance

Lenovo 40-70 ultra-thin notebook no power on no booting, pr302 test, there is no VCC at both ends, and acoff is also the high level of 5V or so, only remove pq311 to see if standby is integrated, and then dismantle pq311 decisively.Power on, standby 0.016, normal.

[machine model] Lenovo 40-70 ultra thinnotebook

[motherboard version] la-a321p

[fault phenomenon] notebook no power on no booting

[maintenance process]

Received a Lenovo 40-70 ultra-thin notebook, fault description according to Switch,no power on,Connect the power supply source found no standby current.Remove the main board and check that there are no 3.3V and 5V and that there is no avcc in EC.

Open Xinzhizao Soft, check schematic, measure pr302, both ends do not have VCC, pq301 D S pole has 19v.The S pole of pq302 has no 19v.It’s obvious that isolation has never been done.According to the drawing, pq301 and pq302 should be lower than 19v, and the actual measurement is basically 19v.

Maintenance drawing 1 of Lenovo 40-70 ultra thin notebook no power on no booting

Check the pacin VCC, one side of pr318 measured is 0V, which is generally less than 2V. This VCC VCC is high level, which seems to have been pulled down.

Again, acoff is also the high level of 5V or so, which leads to pq311 conduction and low pacin.Is this high level from EC?No, EC doesn’t have VCC.Remove pr321 first.The G VCC of pq321 is still in use, and the acoff of EC is 0V.Acoff also has a way to pd301diodeThere is no conduction for multimeter and multimeter.After that, the G pole of pq311 was tested, and it was 16V.Where does the electricity come from?

Maintenance drawing 2 of Lenovo 40-70 ultra thin notebook no power on no booting

Lenovo 40-70 ultra thin notebook no power on no booting maintenance Figure 3

Only remove pq311 first to see if standby is integrated, and then dismantle pq311 decisively.Power on, standby 0.016, normal.After measuring the G pole of pq311, it is 0V low level.It turns out that the internal resistance of pq311 is poor, which causes the high level of G pole not to be released.Replace pq311.Everything is OK on the motherboard.

Lenovo 40-70 ultra thin notebook no power on no booting maintenance Figure 4

Lenovo 40-70 ultra thin notebook no power on no booting maintenance Figure 5