acer d255 la6221p completely dead

[demkat1]

Hello, there I had my d255 on a desk auto updating trhough wifi. after 0.5 - 1 hour I looked at it, the display was black. No led light up. Press on/off button : nothing. Tried many "tips" (hold switch down 10sec, 20sec, 1 min ...) nothing. I disassembled it, got the schematic, the mobo layout and tried.

connect the battery. press on/off :
no led light up
usb power turns on (@ C317).
no 5VALWP, no 3VALWP although at the moment of switch press, there is a slight (mV) change on DVM and then back to zero
switch logic working, although the "3VALW" on this circuit is 11V (battery) and droping to 5V when switch press.

I would like to know the actions, measurements, necessery peripherals attached,
during power on
or any other knowledge - suggestion - opinion

many thanks

[mon2]

Re: acer d255 la6221p completely dead

Hi.

1) Remove the battery. Remove any other add-ons that are not required like SSD / hard drive. Power up again with only the adapter. Any improvements ?

2) With the adapter connected and in the ON state, check the voltages at the attached sites. This is to confirm if the DCIN from the adapter is able to pass through onto the logic board or not.

Post the voltage readings before and after the mosfet.

Meter in 20V DC or higher scale. Red meter probe on point to test; Black meter probe to ground.

[demkat1]

Re: acer d255 la6221p completely dead

ok, battery removed, (everything removed), stays only mobo with led pcb

power with adapter
before mosfet 19V, after mosfet 19V

=power passes thru mosfet.

***ADD : ALL leds remain OFF

[demkat1]

Re: acer d255 la6221p completely dead

charging NOT working :
PQ11 cut off
Vin1 = 0V

[mon2]

Re: acer d255 la6221p completely dead

See attached.

To confirm if PQ11 is defective, remove all power (no adapter / no battery).

Meter in resistance mode (2k or higher is ok).

Measure & post the resistance for:

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

Looking for very low resistance which should denote a damaged mosfet. If a low resistance reading is found, remove the mosfet OFF the board and then measure again that the readings are accurate.

[demkat1]

Re: acer d255 la6221p completely dead

See attached.

To confirm if PQ11 is defective, remove all power (no adapter / no battery).

Meter in resistance mode (2k or higher is ok).

Measure & post the resistance for:

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

Looking for very low resistance which should denote a damaged mosfet. If a low resistance reading is found, remove the mosfet OFF the board and then measure again that the readings are accurate.

#1
got the schematic, the mobo layout

#4
charging NOT working :
PQ11 cut off
Vin1 = 0V

well, since Vin1 is 0 V, PQ11 is normally at cut off mode. No need to remove and check.

Anyway. The problem was a capacitor at +5VS

Have a nice day