Thanks for sharing the information. You're right. The diode around the bios chip is bad possible due to overheat when desoldering. I checked the diode forward bias is ~1.5v, which is not normal, it should be ~0.5v. The large bias pull down the vcc. I need to find the replacement, hopefully the problem would be solved....

Thank you very much for the help. I flashed the bios you provided, but still doesn't work. before I hold ctrl+esc and then plug in power source, the power button will light up. now it looks the computer was not responsive to any button pressing. I think if the bios is bad, ctrl+esc method should trigger the bios recovery process and light up the power button light, right? I measured the bios vcc is only about 1.4v, I am not sure if this is normal voltage as I think the vcc should be 3.3v, right? is it possible the MB or keyboard is damaged?...

I am not lucky to get it work. I used CH341A to dump the original bios, but can not write bios. The error message: chip main memory with the contents are in disagreement. Then I bought a new program tool RT809F, the bios can be write without any error. After installed the chip, my computer doesn't show any response when press power button. I thought it maybe a bad bios file, then I flashed the original bios, the computer still no response to press power button. Is the computer bricked? What's possible reasons cause this problem? is there any solution I can try to get it work. Thanks....

FYI: Dell latitude 7430: HDB30/40/50 LA-L581P, Rev:2.0: ST-6JNCRQ3. chip: 25Q256JVEN...

Attached is my original bios dump. please help unlock the bios. Thanks....

do you know which chip I need to de-solder to save the bios file with programmer?...

what's the tool I can use to dump bios to file?...

Could you help unlock the bios for Dell latitude 7430: HDB30/40/50 LA-L581P, Rev:2.0: ST-6JNCRQ3
Thanks.