Acer Aspire VS-471 notebook occasionally starts screen for repair

Machine model: Aspire VS-471 series

Version 11309-2

Malfunction: notebook occasionally turns on screen is black or frozen

Maintenance process: The received machine is the second mobile phone, and the bridge has been changed, but neither the BIOS nor the EC has been moved. I’m also a little puzzled. Why did no booting directly move the bridge? I don’t know what the fault was at first.

Acer Aspire VS-471 notebook occasionally starts screen for repair figure 1.

Acer Aspire VS-471 notebook occasionally starts screen for repair figure 2.

Acer Aspire VS-471 notebook occasionally starts screen for repair figure 3.

Bare board plug-in standby is a bit big. Press Switch to turn on the screen, and it can also be displayed. Turn it off and turn it on again, and it will be no booting. When the bare board is plugged in for a long time, it can be turned on again. Touching the bridge by hand is a bit hot, and it feels that the temperature is abnormal.

no booting didn’t have 3V and 5V VCC. After pressing Switch, it can be detected that 3V and 5V came out and dropped all the way back and forth. The oscilloscope didn’t find any problem when playing waveform, and RSMRST# also came out and dropped. The standby chip is turned on at current of change.

Because it can be turned on occasionally, I lowered the turn-on of the standby chip, so that 3V and 5V can be directly generated. It still doesn’t work after turning it on again. The 117 pin of U2701 has been tested to be 0V.

Acer Aspire VS-471 notebook occasionally starts screen for repair figure 4.

This is definitely abnormal. It’s still the same after BIOS.VCC and reset are normal. Just change EC, and the result is still the same problem. After a circle in the forum, a master said that temperature control U2801 may cause this problem. It is still the same if it is directly removed.

See if the bridge problem lowered EC’s 117 pin, resulting in no current of change,RTC conditions were checked, DSW VCC was checked, and BATLOW was normal. The result of directly replacing the bridge was still the same.

I still have confidence in BGA Rework Station, and I have no direction. I began to doubt the standby chip, but it still didn’t work when I changed it. But I can’t turn it on occasionally after I changed it this time, so the problem seems to be getting bigger. Test the conditions of EC from the beginning, but it felt wrong when testing ACIN.

Acer Aspire VS-471 notebook occasionally starts screen for repair figure 5.

At the beginning of pick-up inspection, it was tested to be normal, but now it’s not normal. I tested the isolation tube directly and found that PU4001 was not completely turned on. This discovery made me feel puzzled. How can the Current protection isolation of machines that can be turned on occasionally not be completely turned on? I really don’t know if this is the original fault. Please deal with it first!That is, there is something wrong with the 20 pin resistor and Capacitor resistor of PU4003, so they have been replaced directly. When the power is turned on, the standby becomes smaller, and the fault is eliminated.