Asus E410 only works on battery after reverse polarity

[Kervin Mathumbu]

Hi everyone. Fixed my AC and despite trying to be extra careful, I reversed polarity and got a notable pop sound. Now the PC will only work on battery. Windows still shows the battery as charging but the count actually goes down until empty (I have two of the same laptops).

I have board R3.0 so the schematics on another thread here do not match mine. I have tested the BQ charge IC and my pin 1, 2 and 3 have 3.35v each - instead of 18v or 19v. Could this be a bad BQ IC or capacitor? Any thoughtful advise sould be greatly appreciated.

Mobo shows no visible sign of a fried component

[mon2]

Which BQ charger IC? Post topside pics of the charger IC.

Someone cracked under this event.

[Kervin Mathumbu]

Sorry it is BQ24780s

PS. Comparing the BQ24780S voltage readings here https://www.badcaps.net/forum/troubl...arging-battery so far as it is the same IC and laptop model

[mon2]

Post pics of this charger IC. The voltage at these pins is incorrect. Do you see any imperfection on the topside of this charger IC or any other nearby parts? Study where the battery mates with the logic board and continue to review each part to this charger IC.

Alternatively, you will need to very carefully measure the voltage to ground of each and every pin on this charger IC while the battery & power adapter are attached. Post each measurement in a table with their pin number and function label (ie. ACN / ACP, etc.).

If this IC is working and powered correctly and the power adapter is deemed to be suitable, then the ACDRV pin will be boosted to 25 volts to enable the 2 x DCin mosfets. We need to study each of the DCin mosfets to confirm the power adapter voltage is reaching this area and how far is the power path travelling onto the board.

[Kervin Mathumbu]

Greatly appreciated. I meant to add that pin 4 which should be the infered ACDRV had what seemed to be less than 1v instead of 24v. I shall try to double check this in the morning. No the IC has no visible imperfections. And neither does the surrounding components - through to the battery socket. Both my batteries locked up it seems (not working) so I can only measure with the AC connected if drained and locked batteries will be misleading.

[mon2]

Tomorrow - disconnect the battery. Carefully measure the voltage to ground of each pin on the charger IC. The details will help debug this case. Suspect is this IC since REGN is very low. It should be ~6 volts.

The charger IC needs to be powered as well. Best to check each pin as per the datasheet and post the values here.

[mcplslg123]

For sanity, first thing to check is the dc-in mosfets.

[Kervin Mathumbu]

Its near 8AM so I should look into both suggestions shortly. @roman728: assistance in identifying the DC-in mosfets would be greatly appreciated. If I understand well, they are, at best, to be located near the charging jack but my mobo does not seem to be thus structured.

My mobo is the same as this once: https://www.badcaps.net/filedata/fetch?id=2257367

[Kervin Mathumbu]

IC voltages with just the AC:

1. 3.14

2. 3.14

3. 3.13

4. 3.13

5. 5.48

6. 2.55

7. 0.01

8. 0

9. 0

10. 0

11. 0

12. 0

13. 0.28

14. 5.97

15. 0

16. 0

17. 0.22

18. 0.25

19. 0.22

20. 0.22

21. 0

22. 0

23. 0

24. 6.04

25. 5.86

26. 0.22

27. 0.22

28. 18.72

I shall try to label them accordingly if needed. Pin 4 turned out to be 3.13v (this time I used the stock AC adapter unlike at first).

[mon2]

Many of the voltages for this charger IC look healthy. You have REGN @ 6v; VCC to the IC is ok but ACDRV is not.

As suggested by mcplslg123, let us check the DCin mosfets. Nearby this charger IC will be 8 pin mosfets (usually 2 of them; 4 pins on each side). Locate these and share their topside markings.

Alternatively, trace the ACDRV pin of the charger IC to a series resistor (should be ~4k in resistance across the resistor). If checking resistance, remove all power.

Once it is found, the mosfets should be very close to this resistor.

Once you find the resistors, we can check if the mosfets are defective or not. High probability that at least one is defective since ACDRV is not boosted to ~25 volts during a normal operation.

Locate the mosfet and test as follows using resistance mode:

source (1-2-3) & drain (5-6-7-8) ; meter probe on any pin from each group
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. Checking for a low resistance value across the mosfets. Check each mosfet. Post pics of the mosfets so we can inspect for damage.

[Kervin Mathumbu]

mon2
my board is this: https://www.badcaps.net/filedata/fetch?id=3309962 and the BQ24780s is near the battery socket (and is marked on top as BQ...) if you can identify both it and the inferred mosfets and resistor. But I have also seen some mosfets there indeed and will attempt to test them. But the pic above also shows some markings when zoomed it seemed. I shall feedfeedback shortly soon.

[Kervin Mathumbu]

Okay it is located bottom left of the ram chips. I see two mosfet to its left. Assuming those are? And if the said resistor can be visually identified. But I am Trying to test the mosfets now.

[mon2]

The topside mosfets may be for the battery charge circuits but you can check by testing the resistance of pin # 4 of the mosfets and other meter probe on pin # 4 of the charger IC (ACDRV).

If you read a resistance of ~4k ohms then yes, these are indeed the DCin mosfets.

Also inspect the bottom side of the PCB for other mosfets that may be linked to the charger IC.

The mosfets presently of interest will reside between the power adapter connector and the charger IC.

[Kervin Mathumbu]

Two mosfets by the IC are

475 source and drain (and around 16k source and gate)
461 source and drain (around 13k source and gate)

I have one mosfet near the charging jack wi 0.02 source and drain and 0.09 with source and gate. Might this be the culprit or I possibly confused things?

[Kervin Mathumbu]

Measured the same mosfet on my working laptop (identical model) and it reads 530 source and drain. And no continuity for source and gate. Might it be a defect mosfet case or some nearby component that feeds it?

[mon2]

Post pics of these mosfets. Does pin # 4 of these mosfets have a resistance to the ACDRV pin on the charger? If yes, then these are the DCin mosfets.

[Kervin Mathumbu]

Struggling to locate the suspected mosfet pair in short now. Tested a number of mosfets gates but none has a clear continuity to or from pin#4 of my BQ chip. And none shows a 19v input of those mosfets I tested. Feel a little stuck but should continue to acquaint myself more enough these components so that I can make better sense of the guides and suggestions I am receiving from you guys.

pin#4's track sinks to the other side shortly after extending from the IC. With no easy way to track how it continues from there (seems like a dead end of a sort) to hopefully locate the series resistor.

[mon2]

The resistance between the gate pin and ACDRV pin should be ~4k ohms. That is the pair of mosfets we are after.

[Kervin Mathumbu]

Should retry the gates and pin4 in the morning. They all seemed to have 0 resistance essentially. Except one that starts with a sort of resistance but also quickly goes to 0.

[mon2]

See attached.