Dell Latitude E7280 power on for 1 second

[suiramix]

Hi there,
I got this Dell Latitude E7280 in very good condition without battery, plug-in the barrel or USB-C charger and press power button the led is on for just a second and off , cpu fan is not spinning .. measuring the PU901 IC charger voltages , everything looks normal to me (VDDP and VDD = 5.2V, ACOK = 3.1V, ACIN+ 3.6V, CSIN, CSIP= 19.8v). Also PQ905, at D1 =19.5V and PQ904, at D1=12.8V. Could be a short to ground? I will measure the resistance of some coils...did anyone had similar issue ?

[mon2]

Re: Dell Latitude E7280 power on for 1 second

Hi.

1) power down. Meter in resistance mode, check the resistance to ground of each coil. Likely they will be grey in color.

2) still meter in resistance mode, check for shorted mosfets starting at the dcin of the logic board.

Review the resistance chart at this great website:

http://electronicsbeliever.com/how-t...-is-defective/

[suiramix]

Re: Dell Latitude E7280 power on for 1 second

Thanks Mon2 for advice!
First I plugged in the charger and measured some voltages at coil:
PL100, 3.31V (+3.3V_ALWP) OK
PL101, 5.01V (+5V_ALWP) OK
PL201, 0V (+1.2V_DDRP)...
PL301, 1.02V (+1VALWP) OK
PL404, 1.01V (+1.0V_PRIM_COREP) OK
PL901, 19.6V (+PWR_SRC_AC) OK
Without charger ,
PL610 has 13 ohm (+VCC_CORE)
PL612 has 10 ohm (+VCC_GT)
PL614 has 25 ohm (+VCC_SA)
Are those last resistance values kind of low?

[mon2]

Re: Dell Latitude E7280 power on for 1 second

1) low voltage rails are expected to have low resistance. These resistance values are ok.

2) PL201 is at 0 volts? Power down and check and post the resistance to ground for this coil.

3) also check the mosfets local to this coil for possible shorts using the linked webpage - see the resistance table for guidance.

4) be sure your external power adapter has ample current to power this box