Acer Aspire VS-471 Occasionally The Laptop Can Be Turned On Repair

 

Machine model: Aspire VS-471 Series

 

Version number: 11309-2

 

Fault phenomenon: Occasionally The Laptop Can Be Turned On

 

Maintenance process:

 

The machine I received is a second-hand mobile phone. The bridge has been replaced, but the BIOS and EC have not been touched. I am also a little confused as to why I don’t just turn on the machine and directly touch the bridge. I don’t know what the fault was in the first place.

The bare-board plug-in standby mode is a bit large, and the screen can be displayed even when you turn it on by pressing the switch, but it won't turn on when you turn it off and on again. After a while, the bare board can be plugged in and it can be turned on again. The bridge is a little hot when you touch it, and the temperature feels abnormal.

　　There is no 3V and 5V voltage when it is not turned on. After pressing the switch, it can be measured that 3V and 5V come out and then fall off again. The oscilloscope does not find any problems when playing the waveform. RSMRST# also comes out and falls off. The standby chip is also jumping when it is turned on.

　　

Because it can be turned on occasionally, I turned the standby chip low to allow 3V and 5V to be generated directly. But it still didn't work when I turned it on again. I tested that pin 117 of U2701 is always 0V.

       

         This is definitely not normal. After flashing the BIOS, it is still the same. The power supply and reset are normal. I directly replaced the EC, but the result is still the same problem. After looking around the forum, some experts said that the temperature control U2801 may cause this problem. Even if I just dismantle it, the problem is still the same.

　　Check to see if there is a problem with the bridge that pulls down pin 117 of the EC, resulting in no jump. Check the RTC condition, check the DSW voltage, and the BATLOW is normal. If you directly replace the bridge, the result is still the same.

　　I still have confidence in the BGA, but I have no direction. I started to doubt the standby chip, and it still didn't work after changing it. But this time after changing it, I can no longer turn it on occasionally. Now the problem seems to have become bigger. I started testing the EC conditions from scratch, and it felt wrong when I tested ACIN.

        It was normal when I first picked up the machine for inspection, but now it is not normal. I directly tested the isolation tube and found that PU4001 was not fully connected. 

        This discovery made me feel baffled. How could a machine that can be turned on occasionally not be fully protected and isolated? Continuity, I really don’t know if this is an original fault, let’s deal with it first! There was something wrong with the 20-pin resistor and capacitor of PU4003, so I replaced them directly.

After powering on the machine, it also became smaller in standby mode. After troubleshooting and repairing, I still didn't understand what the original fault was in this machine and what the bad things were. 

Only by looking at the expert can we determine the cause of the problem. I think the protective isolation is not completely conductive and should not cause this phenomenon.

Happy Repairing !!