After checking, there is an indicator light on the inserted charger, and there is no boot response when the power-on key is pressed, but the indicator light will go out when the power-on key is pressed, which may trigger protection due to local short circuit. It is found that many capacitors are short-circuited. After removing the short-circuited capacitors, test the other capacitors to ensure that they are not short-circuited. After commissioning, 3.3V returns to normal.
The standby chip is hot, and the short circuit of EC causes LDO 3.3 to be pulled low; Judging from the problem on the EC side, I found that there was a needle attached to 5V, which caused the EC to burn when it was powered on. Pins are broken, and then an EC is changed. The boot is normal, and the fault is eliminated.
First plug in the USB mouse for testing, and the visual mouse light is not on, which is due to the lack of USB+5V power supply. After the flying line, USB_P1 on the small board is connected to USB_P6；; USB_P2 to USB_P4. The test can identify the use of USB devices. Just give up the function of the camera, but don't have to change the CPU at a high price.
Haier's T90-T notebook doesn't start up, and it is preliminarily judged that there is power supply and it can't work normally. The actual measurement shows that SLP_S3# has no voltage. Finally, a brand-new original South Bridge chip was replaced, and ME was configured. The test of the machine entering the system was all normal.
Lenovo Y400 notebook didn't respond when pressing the switch. When the trigger current goes up for a while, the power will be turned off, then the original BIOS will be brushed back, and the machine will be turned on directly.
When the TPN-Q191 notebook is in normal use, it suddenly loses power. Carefully observe the fault phenomenon. After running for 3 days, the power indicator goes out. When it is turned on again, the self-test page reports CMOS error 502. According to the drawings, it can be seen that PQ1(AP0203GMT-HF) and PQ2(AON7408) are isolation tubes. Because PQ1 has a large current, no replacement is found, only PQ2 is found. After the replacement, everything is normal through plug-in test.