Dell 15 5566 LA-D871p

[Sergio Kub]

Hello
I am repairing this board and I encounter the following situation: It does not turn on and does not have the primary voltages, +3VALWP and +5VALWP and the ICs also do not have the EN_3V and EN_5V enablers, which come from the SIO ALWON signal through the PR121 arrangement. SIO has 3 VLP and does not generate this ALWON signal.
The question: is SIO bad?
If anyone has had this experience and can help me, I would be grateful in advance.

[mon2]

Start with the usual DCin mosfets and the charger IC. The ALWP rails will follow after the above mosfets are properly enabled. The DCin mosfets will be enabled by the ACDRV pin on the charger IC so you should have ~25v on the GATE pins of the DCin mosfets.

Moreso, this is a DELL so the ID pin of the adapter is critical. If this adapter single wire communication fails, the logic board will believe the adapter is not capable of powering this load and power down.

[Sergio Kub]

I injected 3.3V into ALWON, pin 126 of the SIO and the 3.3V and 5V voltages appeared, but the board did not turn on

[mon2]

Post # 2.

[Sergio Kub]

I examined the DC input and the PSID (PL2), I think it is the charger identification, it has 0V

[mon2]

Would you have the schematics for this one? Link them in the schematic forum if you do. My database is only offering the boardview file.

[Sergio Kub]

yes, I will post the attachment

[Sergio Kub]

.

[Vesko356]

Schematic and boardview links:

https://www.badcaps.net/forum/troubl...93#post1360493

https://www.badcaps.net/forum/troubl...post1594725

[mon2]

Thanks. Review pq6 mosfet which often gets damaged. Flux and remove it. Then bridge the source and drain pins and test again. If pq6 is defective, the adapter communication will halt for the single wire protocol.

[Sergio Kub]

Hi, can you help me with the board analysis?
I took some voltage measurements on the defective board and one was ok.
Thanks

[Sergio Kub]

Thanks for the feedback. I did the procedure to remove Q6 jump D S, but the board didn't turn on. There is no voltage on this mosfet... I measured resistance for gnd 6 KOhms

[Sergio Kub]

Voltage +19VB on PR703 19V ok
Voltage +17.4V_BATT+ at PR765 0V (without battery connected)

[Sergio Kub]

I compared it with an ok board
OK Bad
pr703 19v 19v
pr765 0v 0v
pr743 19v 19v
pl100 3,3v 0v
pl101 5v 0v
PBATT1 pino 4 5 6 3.3v 0v
PQ6 D 3.3v G 5V S 3.3v G 0V D 0v S 0v

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of PL100. Do the same for PL101. Hunting for a short condition. Post the measurements.

[mcplslg123]

PS_ID wont be available unless 3V ALW is available.This is my understanding. So if resistance reading at PS_ID is ok,then very likely its SIO fault. What is the resistance to GND reading on pin121 of SIO? This board uses MEC1404 as SIO and its known to have dry solder joints. Just apply flux and touchup the pins with solder iron and see if it helps.

PS: La-D871P and LA-D071 is not 100% same though most of the circuit is same.

[Sergio Kub]

PL100 4.84k Ohms
PL101 60k Ohms
No short
I'll try resoldering the SIO

[Sergio Kub]

PS_ID wont be available unless 3V ALW is available.This is my understanding. So if resistance reading at PS_ID is ok,then very likely its SIO fault. What is the resistance to GND reading on pin121 of SIO? This board uses MEC1404 as SIO and its known to have dry solder joints. Just apply flux and touchup the pins with solder iron and see if it helps.

PS: La-D871P and LA-D071 is not 100% same though most of the circuit is same.

resistance to GND reading on pin121 of SIO = 13 Ohms. I isolated the pin and found that this resistance is caused by the SIO
I'll try resoldering the SIO

[mcplslg123]

The resistance is fine. i got alrmed by such a low resistance and concluded that SIO is faulty on a LA-D071P mb.However, after soldering a new SIO mb worked and i checked resistance to GND on pin121 was still 17 ohms in my case. Resoldered the old SIO back and that worked too. So,yes just resolder it.

[Sergio Kub]

Good afternoon,
After carrying out the SIO resoldering procedure, with flux and a soldering iron, the alwon signal appeared on pin 121.
The board still didn't turn on, PR 114 (2.2K) was open, I can't imagine why (2 defects on the same line?).
After changing the PR114 resistor, the board worked and everything was ok.
I would like to thank everyone who collaborated with me to resolve this defect on the Dell 15 5565. LA-D871P board.
I confirm what the friend said, the LA-D071 scheme and the boardview cad are the same and you can work with them on this board.
Whenever I can I will be collaborating here too.
Maybe it gets in the way of me trying to collaborate, sorry.

BADCAPS
The best forum in the world

[mcplslg123]

Whenever,you get a mb with MEC1404/1416/1418 as SIO and missing enable for 3V/5V regulator,always first re solder the sio-Atleast more then half of the cases will be resolved. The problem is most frequent on LA-D071p/La-D871P/La-J081P/La-G717P and many more. Just sharing my experience so that others can benefit.

[Sergio Kub]

Show, valuable information for those who work in the area.
Thank you very much