Acer Aspire 3 LA-H792P no 3.3V or 5V, only 19V

[Serbentas]

Hi guys,

Please help. Acer Aspire 3 LA-H792P only 19V on. Missing 3.3 V and 5V and rest of course. What creates these please?

Thanks so much

[mon2]

Re: Acer Aspire 3 LA-H792P no 3.3V or 5V, only 19V

Hi. Where are you measuring the 19V ?

See attached -> check if the 19v reaches the main power rail (on the right of the schematic).

That is, the trouble is often in the DCin mosfets that are highlighted.

Measure the voltage on each pin of the mosfets to confirm their operation.

[Serbentas]

Re: Acer Aspire 3 LA-H792P no 3.3V or 5V, only 19V

Yes, reaches. And 19V goes everywhere like to PL501 and PU301 and so on

[mon2]

Re: Acer Aspire 3 LA-H792P no 3.3V or 5V, only 19V

Each power rail has a local ENABLE pin - see attached.

Confirm the voltage of each enable pin. If the rail is enabled, then the LDO and the switching rail should be ON. Each rail has its own enable pin.

[Serbentas]

Re: Acer Aspire 3 LA-H792P no 3.3V or 5V, only 19V

PU301 pin 11 4.5V pin 12 0V
PU301 same pin 11 4.5V pin 12 0V
That's as far as I got. Can figure it out where those missing are coming from

[mon2]

Re: Acer Aspire 3 LA-H792P no 3.3V or 5V, only 19V

Confirm the voltage on the 3v3 and the 5v0 LDO rails - are they working ? (since their enables are OK).

UPDATE:

UB1 (Pin #104) is linked to the 3V_EN for the switching power supply. If you are reading 0V for 3V_EN then it is possible that UB1 is not working correctly. UB1 requires the +3VLP LDO to be working so it can be powered.