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Lenovo Flex 6-14 brought back to life except…

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    Lenovo Flex 6-14 brought back to life except…

    Received this Flex 6-14IKB, DOA, the owner was pretty sure the problem was the charging port as the computer had stopped charging the battery. Tried a different battery, same result (the laptop worked fine while it had sufficient battery). Tried replacing the charging port for good measure, no change. Found that one of the main power IC’s PU301 was lacking readings basically all the way around it, so i changed that as well just in case. But found a bad mosfet that supports PU301, changed it, resulting in proper readings on PU301 and for the first time got sign of life—amber led’s at the charging port and power button, fans spin momentarily while the keyboard backlight lights up, but display is black and no reports of prior problems with the display. It does this loop endlessly, regardless of whether both power cord and battery are plugged in, or just power cord. These symptoms looked a bit like firmware issues, so i inspected further and found a missing resistor next to the firmware chip. The specs in the schematics indicate 0402 size, 15, and 5%. I soldered in a new 0402, 15ohms, 5% tolerance resistor, and the flashing led behavior etc was the same. I could not find any power rating in the schematics for this resistor, so i used 1/16W. Perhaps the problem is here? The laptop does not post, so I also tried removing ram, replacing ram, and disconnecting any non-critical component from the motherboard. Still the same thing with the led’s/fans/kb loop. Again, the laptop worked fine previously while it had enough battery juice. I’m theorizing the damage resulted from using a 19V power adapter for about a year instead of the spec 20V. Any ideas out there?
    Last edited by SanDiegoHB; 02-16-2022, 11:15 PM.
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