It is found that there is secondary power supply in front of R4001. After passing R4001, there is no power. If the resistance value of the measured resistor is good, C4023 will be short-circuited, replaced decisively and repaired.
Found that standby is 0. According to the drawing, measure each pin of the chip, burn the machine directly, and feel that the PC388 capacitor is seriously hot, and it will not be short-circuited after being pulled out.
Check "About this machine" and find that there is no baseband, make up the dropped inductance and install the motherboard into the machine. Boot test shows that the version of "Modem Firmware" in "About this machine" is normal, indicating that the baseband has been working normally.
3V standby, replaced by an AMS1117-3.3, suspected that there is something wrong with the graphics card chip, turned off the power, removed the power supply inductor of the graphics card, and powered on again. The machine runs normally, the fault is repaired, and the maintenance is over.
IPhone XS Max mobile phone screen is not displayed, and it is found that the resistance of PMU_TO_DISPLAY_RESET_CONN_L line at pin 5 of the cradle is unstable. Scrape the PCB board, reconnect the lead of PMU_TO_DISPLAY_RESET_CONN_L, and repair the fault.
There was no response when pressing the power button. I found that the vicinity of the USB conversion chip was hot, and the chip was removed, or it was against the ground, and the capacitor next to it was removed. Power-on test, perfect lighting!
Firstly, the step-down circuit was measured, and it was found that there was a resistance between the capacitors connected at both ends of the charging step-down inductor, so a rich inductor was replaced.
Check the small board and find that there is corrosion next to the microphone. Remove the chip, clean the pad and redo the filter next to it. Boot test, perfect repair.
Machine model: Glory X30i
Lenovo notebook Y7000 2019 boot screen, found that the graphics card model is 2060, drive exclamation point, error 43. After removing the main memory, everything will be easier. Deal with the pad first, and then solder the new memory.
