acer a314-41 dead

[salawayon]

board info:
RAICHU_SR
18762-1448

@ PU4301 (SM4378):
D - 19v
S - 0v
G - 0v

@ BQ24781:
pin28 - 19v
4 - 0v

can't find any short circuit. tried already changing BQ24781 with BQ24780s. i tried to bypass PU4301 and PU4401 and the unit will power up with display.
anyone could share a schematics for this unit?

[mon2]

Re: acer a314-41 dead

Post all voltage readings to ground of the charger IC with the adapter connected.

[salawayon]

Re: acer a314-41 dead

@ BQ24781:
1-0V
2-0V
3-0.147V
4-0v
5-3.4V
6-2.85V
7-0.161V
8-1.2V
9-0V
10-1V
11-0V
12-0V
13-0V
14-0V
15-0
16-0
17-0.14V
18-2.4V
19-0.149
20-0.149
21-0.389
22-0V
23-0V
24-6V
25-5.72V
26-0154
27-0.152
28-19.39V

[mon2]

Re: acer a314-41 dead

Hi. Did you locate the schematics? I have them but it is tied to a paid service so let me share the relevant portions of this schematic.

The charger IC is a common BQ series from TI. Respectively, TI chargers like to use N-channel mosfets.

There are 2 x DCin mosfets (as per the sticky article above by @Piernov - a must read).

Often, faults like yours are linked to the 2nd DCin mosfet = PU4401.

The ACDRV drive voltage to enable the 2 x DCin mosfets should be ~25 volts if all is normal.

This value is based on AC ADAPTER voltage + REGN pin voltage = 19v + 6v = 25 volts.

There is a series resistor of ~4k @ PR4421 that drives the 2 x DCin mosfet's gate pin.

As a test, you can remove this part but do not lose it. Then power up again.

Do you now see the ACDRV pin @ ~25 volts ? See attached.

PS: Very late for you so proceed with caution.

[salawayon]

Re: acer a314-41 dead

thank you for your inputs. i already solved the problem before i even read your reply. i just replaced PU4301 just by trial and error cause i can't detect any short circuit on PU4301.
resistance between pins @ PU4301:
D-S = 2.362Mohms
D-G = 5.2Mohms
S-G = 2Mohms
when applying positive supply at G pin, PU4301 won't function.

[mon2]

Re: acer a314-41 dead

Awesome! Well done.

[mcplslg123]

Re: acer a314-41 dead

I'll keep my fingers crossed and i beleive it'll return to bench with same problem very soon. A problem cant be solved by replacing a component which is not defective. I doubt, its the heat applied during soldering/de-soldering is at play here.