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[dellxps15]

what value in L7520 in diode mode ?

is fuse f7140 100% ok ?

[dellxps15]

best way is to use scope and check whole board for spme corrotion or something strange on it....

[dellxps15]

check u1950 voltage.... can be bad u1950... check all_sys_pwrgd if stable at 3,3 volt of it do on off.

[dellxps15]

easy question.... are sensing resistor ok ? r7121 r7122 (10omh each) u can check pin 27-28 of u7100 if it's 20 omh. also check r7151 r7152.

[dellxps15]

fan spin for 1 sec then stop and no loop or it do fan spin every tot seconds ? when u plug magsafe, fan spin then stop and stay in stop mode also if u wait like 60 seconds ? check bios area, bios spi connector for corrosion, check cpu data lines. also check r1270, r1275 also l1290, l1275 and so on in that area

[dellxps15]

check if cpu vcore comes when fan spin.

[dellxps15]

connect a cable from pp3v3_s0_bkl_vddio to lvds_bkl_pwm_rc