Dell 15-5570, CAL50/DAL50 LA-F115p - Does not detect original charger

[toniu-massa]

Hello, everyone!!! Happy New Year to all!!!

When I turn on the laptop, the warning appears: You have attached an undersized 0W adapter and blah, blah, blah... The bios says that the adapter is not connected and the battery status is excellent.

This laptop has all the voltages at the input, and the charger IC is also normal. There is 3.3V at the PS_ID and I have already tested it with another adapter, also original. The adapter detector also seems to work normally. I am suspecting the SIO. What do you think?

On my portable oscilloscope there is a PS_ID signal. The oscilloscope does not seem to be able to show the waveform, but it is clear that it is a square wave.

The PU1 ended up getting damaged when I was doing the analysis, I changed it and it's still in the same situation. I don't know what caused the PU1 to burn out.

DC_IN = around 20V;
PS_ID = around 3.3V;
AC_OK = I don't remember how much it was, but there is voltage there;
HW_ACAVIN_NB = around 1.7V (at the PUS01A output);
+SDC_IN = around 19V;
+3.3_VBUS_IN = around 3.3V (at the PUS04 output);
HW_ACAV_IN = high level (at the PUB02 output);

In other words, is it not normal? Isn't it the SIO?

I thank everyone in advance for any help

[mon2]

Remove all power. Measure the resistance across PR1. It should be ~33R (ohms).

Confirm that you see ~3 volts on PL3. If not, then remove and replace PQ1 which is often defective or for now, flux and remove it. Then short the source & drain pads on the removed PQ1 pcb pads for testing.

[toniu-massa]

Remove all power. Measure the resistance across PR1. It should be ~33R (ohms).

Confirm that you see ~3 volts on PL3. If not, then remove and replace PQ1 which is often defective or for now, flux and remove it. Then short the source & drain pads on the removed PQ1 pcb pads for testing.

PR1 = around 33R;
PS_ID = around 3.3V = PR1

[mon2]

Test the voltage @ PL3 to ground.

[toniu-massa]

Test the voltage @ PL3 to ground.

PS_ID is on the same rail as PL3. This is in the schematic

[toniu-massa]

According to the datasheet for this SIO, it seems that the voltage at HW_ACAVIN_NB should be 3.3V. I'm reading around 1.7V. The voltages at pins 2 and 3 of PUS01A are correct, pin 8 has 3.3V. This AOP has positive feedback and I don't know exactly what its output voltage should be.

PUS01A:
pin 3: around 1.7V
pin 4: around 1.4V
pin 8: around 3.3V
pin 1: around 1,7V = HW_ACAVIN_NB

Any OAP will subtract the input voltages and amplify them by its gain. In other words, 1.7V - 1.4V = 0.3V; and according to the LM393 datasheet, it has a gain of 200 that will saturate because the supply voltage is 3.3V. So, it should have about 3.3V at its output. That is if we ignore the positive feedback.

According to this reasoning, this AOP is defective, right?

[toniu-massa]

I'll try lifting pin 1 to see if the voltage returns to normal.

[mon2]

pin 4: around 1.4V

?? Pin 4 = ground.

[toniu-massa]

?? Pin 4 = ground.

kkkkk Sorry!!!

It´s pin 3, Around 1.7V

[toniu-massa]

I'll try lifting pin 1 to see if the voltage returns to normal.

It's not the AOP... Voltage rose to about 4V after lifting pin 1

[py2eb]

It's not the AOP... Voltage rose to about 4V after lifting pin 1

Maybe the EC is bringing down this tension.

[mon2]

Yes, the EC is used to determine if the power adapter is suitable or not using the documented 1-wire interface by Dallas Semiconductor (also available under Maxim / Analog brand names as Maxim purchased Dallas Semiconductor IP and then Analog acquired Maxim Semiconductor). If your scope offers a logic analyzer plug in for 1-wire protocol, you can decipher the traffic.

This logic board supports the coax / barrel and also USB-C type power adapters. The PSID is only linked to the coax / barrel connector. Can you confirm you are using this style?

Was PU1 replaced with exactly the same part #? This is critical since the VIN is very high from the raw voltage of the power adapter @ ~19-20v. Most LDO regulators cannot support such a high VIN. Remain with the original part #.

Respectively, you should have 3v3 @ PU1, pin #5 - confirm this.

Next, follow the logic of the adapter selection - what is the voltage to ground of PU2, pin #2? This should be a logic '1' = high to denote the barrel style connector is used for the powering of the board.

Review carefully UE1 for damage as the PSID travels to this dedicated controller to gauge the power adapter rating. Be sure that the barrel connector pin is truly mating with the logic board. This will be the needle like center pin in the connector. If this pin is bent or damaged, the PSID will fail.

[toniu-massa]

This logic board supports the coax / barrel and also USB-C type power adapters. The PSID is only linked to the coax / barrel connector. Can you confirm you are using this style?

This board does not have PU2 soldered on the board. So, it does not support USB-C type adapter.

Was PU1 replaced with exactly the same part #?

Respectively, you should have 3v3 @ PU1, pin #5 - confirm this.

Yes, it was replaced with the exact same part. Pin 5 is around 3.28V

Next, follow the logic of the adapter selection - what is the voltage to ground of PU2, pin #2? This should be a logic '1' = high to denote the barrel style connector is used for the powering of the board.

As I said, PU2 is missing on this board, but HW_ACAVIN_NB is connected to pin 2 of PQ15 through PR46 and has around 1.7V. I think this voltage should be 3.3V instead of 1.7V.

And by the way, I removed PUS01A from the board for testing purposes, and the board didn't change its behavior at all. And even so, its pin 1 continues to present around 1.7V.

[mon2]

What is the Vcc on PUS01A? It should be ~3v3 or very close to this value.

Also suggest to remove all power, meter in resistance mode - measure the resistance to ground of HW_ACAVIN_NB. Need to confirm this signal line is not being loaded.

If the resistance is ok, consider to replace PUS01 = AS393MMTR. This is in a MSOP8 package. The part should be available from many vendors. Hunt for 'LM393' but confirm the same package and pinout. Jellybean part.