Dell Latitude 7280 does not recognize charger

[PowerAmpFreak]

I have a Dell Latitude 7280 which complains during boot-up that the charger wattage cannot be determined. Tested with two different chargers.
Any common faults that could be fixed?
I replaced the DC jack, the original DELL LATITUDE 7280 DC30100Z300 0DP4VC.
How does the communication between the charger and the PC work?

[mon2]

Common fault with the PS_ID pin used by Dell. Tons of articles on this forum on the same issue.

Which logic board do you have in your box? Is it LA-E121P?

Review the PS_ID pin and test its voltage to ground with the power adapter attached.

[PowerAmpFreak]

Voltage on pin 1 is not stable. It floats 0.5-0.6V

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground on the same PS_ID line that mates with the DC adapter. We are testing if the ESD diodes are defective from an ESD event.

If the resistance is low, then PD4 is most likely defective. Flux and remove PD4 and measure again.

Test the voltage on each side of PR5. This must be ~3v3. Then remove all power and confirm that PR5 is ~33R ohms. This resistor is one of the common faults of this issue.

Another point of failure is the mosfet @ PQ2. Test each of the above and post your results.

[PowerAmpFreak]

Thanks. I cannot locate the parts on the PS line. I suspect they are on the other side of the pcb since there is a via directly at pin 1 on the DC jack connector. Do you have any documentation where to find them?

[SMDFlea]

Thanks. I cannot locate the parts on the PS line. I suspect they are on the other side of the pcb since there is a via directly at pin 1 on the DC jack connector. Do you have any documentation where to find them?

A schematic & boardview might be available but you will need to find the motherboard model number, it is probably silkscreened on the other side of the board, so you will have to take it out of the chassis. Disconnect the battery (and charger) first before removing the SSD ,ribbon cables etc.

Which logic board do you have in your box? Is it LA-E121P?

[PowerAmpFreak]

Yeah I was afraid of that. I think in this case I will not risk it taking out the complete MB. Just a question:
What components are in the charger to "tell" the charger wattage? Is it just a resistor? Or digital communication?

[mon2]

Digital communication. This is called the 1-wire interface by Dallas Semiconductor. The fault is often in the path from the adapter ID pin to the EC controller on the logic board. A common issue with Dell.

[PowerAmpFreak]

OK, so could not hold me back to dissassemble it.
It is LA-E121P Rev 1.0

ESD diode PD4 is toasted
I think when the DC jack broke, the charger 19V did contact the ESD diode.

Now works with a replaced diode.

THANKS for all support

[mon2]

Well done!