Acer Aspire 3 ( dh5jv la-g021p Rev:1)

[Jane]

I do not have +3VALW neither +5VALW. These voltages should be generated by PU401, see the picture. LDO3 and LDO5 are present. But there are no 3V_EN ( pin EN2) nor 5V_EN (pin EN1).
Are these 3V_EN and 5V_EN voltages generated by SIO and thus SIO is faulty ( because no voltages?

[mon2]

First check if sio is being powered.

[Jane]

yes, SIO is powered - about 3.3V.
Can you please have a look at the picture below? PU401 is the IC in question - not receiving Enabled signals from SIO. But from the picture you can see that PU401 should provide input power to SIO.
Or am I wrong ?
Thank you for advice

[mon2]

Correct that PU401 is the power supply for the SIO via the +3VLP LDO rail (pin #3 of PU401 is the LDO creator for this rail). The SIO (KB9022) is a stand alone microcontroller (8051 derivative) that will have its own firmware and respectively its own task to monitor the keyboard scanning, real time clock, etc. including enabling the heavier duty power rails linked to PU401 and others. That is, the LDO rails are wimpy low current power rails used by low current devices so that the battery does not drain too quickly. Only when the power button is pressed, the SIO will then perform its duty to enable the main parts of the logic board.

If the SIO is not working to create these enable lines - check:

a) remove all power -> check the resistance to ground of 3V_EN. Is it a low resistance? If yes, there is a fault on this line.
b) Still with no power -> check the resistance from the SIO pin which creates this same signal to the PU401 pin. This trace check should be ~1k ohms (R3926) else the trace is broken or is defective. Confirm that R3926 is ok.
c) SIO will require a clock like any other CPU / microcontroller - need to confirm but most likely this is an external clock source. Is this clock running?
d) It is possible that the SIO firmware has been corrupted. I believe that the KB9022 has an internal flash device but you will need a programmer tool to reflash it unless the logic board permits this process via the main bios. Others on this forum are more knowledgeable about the SIO functions. To do list is to build an affordable reflash tool for this target. It is a back burner project for the community.

[mcplslg123]

3V_EN_R_EC is present? To me this appears like a classic acer thermal protection for which i've provided solution in this forum earlier. But first,give us the measurement i asked for.

[Jane]

Thank you for replies

@mon2

a) remove all power -> check the resistance to ground of 3V_EN. Is it a low resistance? If yes, there is a fault on this line

It is 8.8 kOhm ( pin 4 of PU401 to GND)

b) Still with no power -> check the resistance from the SIO pin which creates this same signal to the PU401 pin. This trace check should be ~1k ohms (R3926) else the trace is broken or is defective. Confirm that R3926 is ok.

Resistance is about 963 Ohm

@mcplslg123

\]
3V_EN_R_EC is present? To me this appears like a classic acer thermal protection for which i've provided solution in this forum earlier. But first,give us the measurement i asked for.

No voltage

[mcplslg123]

Did you check 3V_EN_R_EC voltage after pressing the power button? If no measure after power button pressed.

[Jane]

Yes, I did .
When I keep ON/OFF pressing ( shorting SWK1 ) the voltage fluctuate from about 0.2 to 0.9V

[mcplslg123]

Try to flash the SIO first.