Acer nitro 5 bq24781 no acdrv

[elsomer]

Hi people, i have an acer nitro 5 with motherboard model gh51m la-k861p , it came with the resistor pr103 blow up, i repaced that resistor, i check the coils plb2, pl301, pl501 and has no short to ground, i conect the charger and it doesnt power at all, i check pqb3 on pin 5 to 8 and its 19v, pin 1 to 4 its 0
so i repaced, pqb3, pqb4, and makes no change, still no acdrv, i replaced bq24781 and makes no change, still no acdrv, if someone can help pls, thanks, this are the schematic and boardview

[MOD EDIT] LINK to schematic & boardview -> https://www.badcaps.net/forum/troubl...55-57-la-k861p

[mon2]

1) With no power to the board, measure the resistance (not diode mode) to ground of PQB4 (drain pins 5-6-7-8). Checking to see if the main power rail is shorted or not.

2) Carefully, measure the voltage to ground on PUB1 for pins:

(connect your power adapter)

ACDET ; pin 6
VCC ; pin 28
REGN ; pin 24

Post each measurement.

[elsomer]

Hi mon2, thanks for answer, pins 5 to 8 of pqb4 has no shorted rail here are the values of pub1
acdet: 0v
vcc : 19.5v
regn : 0v

[mon2]

What is the voltage to ground of ADAPDET ?

[elsomer]

it has no shorted rail ,the value on resistance mode is 62kohm , im checking that value on cap pcb18

[mon2]

See attached. Need to review the mosfet gate voltage.

[elsomer]

Prb36 which is on the line adapdet is 5.8v and pin 1 on pqb11 is 5.8v

[mon2]

The ADAPDET pin on the DCin power adapter is not connected. When the power adapter is connected, this line should be LOW which will turn OFF PQB11. Once PQB11 is OFF, the ACDET voltage will be at the proper threshold > 2v7 and the charger IC should enable ACDRV.

Test the theory by shorting PQB11 gate pin to ground. Summary - power adapter connector contact may be loose.

[elsomer]

Test the theory by shorting PQB11 gate pin to ground, i did this and now acdet is 2.6v

[elsomer]

this means i need to replace pqb11?

[mon2]

No. Just connect a piece of wire between ground and the GATE pin on PQB11. Have the power adapter connected as well.

If the adapter is the proper one for this model, it will supply the ~19v.

OR

Flux and remove PQB11 for testing. This will allow for ACDET to return to a normal value. Confirm it.

[elsomer]

yeah, laptop is working perfect without the pqb11, do i need to replace it? or is there any risk of using the laptop without it?

[mon2]

The detection of the adapter is through this tiny circuit area we have reviewed today. Technically, if the power adapter is disconnected, then this ACDET voltage will also go to zero volts (since the voltage is based on the adapter voltage being lowered by the resistor based voltage divider) so from a quick review - yes, it is safe to leave it as-is. Perhaps wait on other techs to chime in for their view but looks ok to me.

[elsomer]

ok, thank you very much for help me , i learned a lot

[mon2]

You are quite welcome