Acer A314-31 (Z8P) No Power

[mullspeed]

I have one of these in for repair, initially found that the 5V regulator had a shorted output that caused the DC adapter to go into protection mode.

Replaced the 5V reg and now I get 5V and 3V3 ok but pressing the power button (well shorting the pins on the keyboard connector) does nothing. I get no lights at all.

I noted that the battery was completely flat, with that removed I only get 2.7V on the battery connection. I thought that would go to the battery max charge voltage?

If I do connect the battery (even flat). I get the orange charging light, which then goes blue but nothing else happens.

There are no obvious shorts and nothing gets warm, I'm stumped. Happy for any and all advice.

[mon2]

Re: Acer A314-31 (Z8P) No Power

Hi.

Start with PU2 (charger IC). Plug in the adapter.

See attached. Post the voltages for the requested areas.

If you do not see close to the DC adapter voltage on Vin junction, then measure and post the voltage readings for the mosfet to the left @ PQ6.

Post the voltage (meter in DC volts; 30V or higher is good) for

source (1-2-3)
gate (4)
drain (5-6-7-8)

pins.

[mullspeed]

Re: Acer A314-31 (Z8P) No Power

Vin = 19.12V

ACok = 1.7mV

Did some measuring around, gate of PQ20 is 2.78V which is the same as BAT-V but the gate and source aren't shorted when the board is unpowered.

[mon2]

Re: Acer A314-31 (Z8P) No Power

Post all voltages on PU2 with adapter attached.

[mullspeed]

Re: Acer A314-31 (Z8P) No Power

Pin Voltage
1 19.12
2 19.17
3 11mV
4 0V
5 2mV
6 2.78V
7 0V
8 3.38V
9 3.38V
10 0.813V
11 3.38V
12 2.77V
13 2.77V
14 0V
15 0V
16 6.09V
17 5.92V
18 2.77V
19 2.77V
20 18.65V

[mcplslg123]

Re: Acer A314-31 (Z8P) No Power

Cmsrc is missing on pin3 . Without valid cmsrc input, acdrv(pin4) will not work. Pin4 controls the dc in MOSFETs gate. If u don't get proper voltage at gate, 19v will not cross after 2nd MOSFET . So do check these points as well as dc in MOSFETs for shorting.

[mullspeed]

Re: Acer A314-31 (Z8P) No Power

Nothing appears shorted, unless it's the IT8987E/CX AC_Protect line

[mcplslg123]

Re: Acer A314-31 (Z8P) No Power

Where is the measurement for dc-in mosfets voltage reading on D-S-G pins?? If you want to draw your own conclusion without diagnosing, thats your choice and we can hardly help without the info provided.

[mullspeed]

Re: Acer A314-31 (Z8P) No Power

PQ6
D 19.28
S 19.28
G 9.53

PQ17
D 2.78
S 19.14
G 19.08

PQ16
pin 1 19.19
2 19.19
3 19.27
4 9.53
5 0V
6 0V