DELL LA-B441P not charging

[Crabolog]

Hi, could someone please advise, the laptop shows that it is charging, but actually it's not. It is still working from the battery, but won't work from the AC.

Here are some measurements from the PU200 charging controller:
1 ACN 19.05v 194k
2 ACP 19.05v 190k
3 CMSRC 17.76v 43k
4 ACDRV 19.95v 40k
5 ACOK 3.1v 140k
6. ACDET 3.1v 6k
7. IADP 0.23v 122k
8 IDCHG 0.36v 184k
9 PMON 0.05v 20k
10 /PROCHOT 0.001v 293ohm
11 SDA 0.393v 33k
12 SCL 0.394v 33k
13 CMPIN 1.7v 1.4m
14 CMPOUT 1.7v 1.4m
15 /BATPRES 0.54v 132k
16 CELL 5.35v 182k
17 BAT 4.1v 363k
18 /BATDRV 0.17v 80k
19 SRN 4.1v 130k
20 SRP 4.1v 126k
21 NC 5.3v 210k
22 GND 0v 8ohm
23 LODRV 0v 255k
24 REGN 5.4v 252k
25 BTST 5.15v 0.65m
26 HIDRV 4.09v 442k
27 PHASE 4.09v 62k
28 VCC 19.28v 0.71k

Measured without a battery, resistance was measured without a power supply.

I think ACDRV might be a bit low, not sure why.

[mon2]

Re: DELL LA-B441P not charging

Yes. Pins 11&12 are also low. Each should be 3v3.

Check the dcin mosfets which are driven by acdrv. If either is defective, acdrv value will be lower. Remove with care the ~4K resistor on acdrv but do not lose the resistor. Power on. Is acdrv pad now ~25v ?

[Crabolog]

Re: DELL LA-B441P not charging

I was about to do it, but was not able to locate PR204 so far, still looking

[Crabolog]

Re: DELL LA-B441P not charging

Well I've removed PR204 and nothing changed, 19.56v. Same zero on 11 & 12 pins

[mon2]

Re: DELL LA-B441P not charging

CMSRC voltage is quite low with respect to the adapter dcin voltage.

1) Can you confirm this measurement again?

2) Next - remove all power. Meter in resistance mode.

Measure the resistance across the DCin mosfets.

source & drain
source & gate
gate & drain

Post each measurement. Checking for leaky mosfets with a resistance check.

[Crabolog]

Re: DELL LA-B441P not charging

I can confirm that without PR204 there is still 19.56 on ACDRV
Also after removing PR204 voltage of CMSRC raised from 17.7 to 19.5

I've measured two dc-in mosftes PQ203 & PQ205 but got kOhms/mOhms everywhere. the lowest resistance was ~100kOhm which seems fine to me.

11 and 12 pins still 0 volts.

[mon2]

Re: DELL LA-B441P not charging

The dual mosfet may be defective with 100k resistance.

reference:

https://electronicsbeliever.com/how-...-is-defective/


Q: What is the resistance to ground of the REGN pin? This is a low current LDO and should be ~6 volts (your posted measurement is lower). The charger IC may be defective.

Also, ACDRV should be boosted under the shared conditions.

reference:
https://e2e.ti.com/support/power-man...acdrv-question

[Crabolog]

Re: DELL LA-B441P not charging

Something weird is going on.

Resistance of REGN is approx 200kOhm, but voltage went to zero (pr204 is still removed)
Also, on charger IC
27 pin now has 19.1v
26 pin now has 18.9v
25 pin has 18.7v

I'm about to replace charger IC

[Crabolog]

So I've replaced the charger IC, but it's still not charging.

[mon2]

Measure and post all the voltages on the charger ic. Proceed carefully while the adapter is connected.

is acdrv now ~25v? Regn at 6 volt?

[mcplslg123]

The dc-in mosfets biasing is incorrect but still 19V is reaching CLR. Confirm whether 19V is reaching CLR. If indeed 19V is reaching CLR,then you should have 3V LDO present on motherboard and in turn SDA/SCL should be 3.3V also. Btw, whats the marking on charging chip.Is it BQ24780s?