Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

[lgcyber]

Hello guys can you check if my analysis is correct? No 3.3v in EC_RSMRST# pin power button pressed or not. After pressing power button, 3V_EN will have 3.3v then back to 0v so PU301 will not produce +3VALW and the laptop will not turn on. I've checked the resistance of 3V_EN pin and it is not shorted. Is it because the SIO is defective already or do I need to reprogram it? By the way, is this SIO ENE KB9052QD programmable? I've included the Boardview and a reference schematic diagram LA-K092P(No KA-K093P available). Thanks to all who will answer.

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

Hi. Have not reviewed your schematics but start with the basics. The sticky above by @Piernov is a must read on how charging works.

Do you have the usual 19v from the power adapter?

Start at the dcin connector and confirm how far this voltage travels. There will be typically 2 x DCin mosfets. What voltage to ground is on each pin of these mosfets?

Often the 2nd mosfet gets killed on laptops.

With voltage and resistance checks with your meter, we can find the defective parts.

Start with the mosfet voltage checks of the source, drain and gate pins. If the gate pin is not ~25v on each, then one of the DCin mosfets is defective and must be replaced.

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

Hi. Have not reviewed your schematics but start with the basics. The sticky above by @Piernov is a must read on how charging works.

Do you have the usual 19v from the power adapter?

Start at the dcin connector and confirm how far this voltage travels. There will be typically 2 x DCin mosfets. What voltage to ground is on each pin of these mosfets?

Often the 2nd mosfet gets killed on laptops.

With voltage and resistance checks with your meter, we can find the defective parts.

Start with the mosfet voltage checks of the source, drain and gate pins. If the gate pin is not ~25v on each, then one of the DCin mosfets is defective and must be replaced.

Thank you very much for your reply. To answer your questions.

Do you have the usual 19v from the power adapter?
Answer:
Yes 19v is present in the DCIN Jack up to the first mosfet.

Start at the dcin connector and confirm how far this voltage travels. There will be typically 2 x DCin mosfets. What voltage to ground is on each pin of these mosfets?
Answer:
I never tried to check on the 2 DCIN mosfets because the SY8286CRAC 5VALW IC is functioning normally with 19V present at VIN so I assumed that the 19v rail is funvtioning normally. Based on the power sequence on page 5 of the schematics, the5VALW line is the one initially present and the 3VALW line will come up after pressing power button sending the ON/OFFBTN# signal then 3V_EN will come out from the EC to enable the 3VALW regulator. However upon checking, when you press the power button, 3V_EN will have 3.3v then after 1-2 seconds it will return back to 0v thereby turning off the 3VALW IC almost instantly. This I think is the problem. Why can't the 3V_EN signal maintain its voltage. What is pulling it down? The 3V_EN line is not shorted to ground upon testing. Do you think this is an EC/SIO problem? By the way RSMRST# also has no 3.3v present before pressing power button and after pressing power button. It remains 0v even with battery or adapter present.

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

It is still good to check the 2 x DCin mosfets for leakage / defects. Often the 2nd mosfet is killed and is a common fault. With a possible leak, the ALW rails will still receive their power (via +19VB).

You can do a quick check with NO POWER / NO BATTERY to the logic board.

Meter in resistance mode.

Check the resistance across the mosfet pins:

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

Post each resistance reading. Repeat for the 2nd mosfet. If the resistance is low, the mosfet is leaking and must be replaced as a part of this repair.

So investigate PQB3 & PQB4 for their resistance.

With the power on, what are their GATE (4) voltage to ground ? This voltage, for n-channel mosfets, must be DCIN+6 volts =~25 volts to enable. Confirm it.

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

It is still good to check the 2 x DCin mosfets for leakage / defects. Often the 2nd mosfet is killed and is a common fault. With a possible leak, the ALW rails will still receive their power (via +19VB).

You can do a quick check with NO POWER / NO BATTERY to the logic board.

Meter in resistance mode.

Check the resistance across the mosfet pins:

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

Post each resistance reading. Repeat for the 2nd mosfet. If the resistance is low, the mosfet is leaking and must be replaced as a part of this repair.

So investigate PQB3 & PQB4 for their resistance.

With the power on, what are their GATE (4) voltage to ground ? This voltage, for n-channel mosfets, must be DCIN+6 volts =~25 volts to enable. Confirm it.

Thanks for your advice. I will not take it for granted from now on.
Upon checking PQB3 and PQB4 here are my resistance readings:

1st MOSFET PQB3:
Source and Drain = 2.45 Megohms
Source and Gate = 2.59 Megohms
Gate and Drain = 4.48 Megohms

2nd MOSFET PQB4:
Source and Drain = 3.38 Megohms
Source and Gate = 2.60 Megohms
Gate and Drain = 3.19 Megohms

With power on, here are my voltage readings for PQB3 and PQB4 :

1st MOSFET PQB3:
Gate Voltage wrt Ground = 25.28v


2nd MOSFET PQB4:
Gate Voltage wrt Ground = 25.27v

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

[mcplslg123]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

Open PJ301/501 one by one and see if 3V_EN becomes stable.

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

Open PJ301/501 one by one and see if 3V_EN becomes stable.

Hmmm nice idea. I'll open PJ301 first and I'll post the result. Thanks very much for the help.

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

Open PJ301/501 one by one and see if 3V_EN becomes stable.

Sadly. 3V_EN did not become stable even after opening PJ301 and then PJ501.

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

On pu301, what is the voltage to ground of +3VLP ?

What is the voltage to ground of pin 11 (EN2) of pu301?

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

On pu301, what is the voltage to ground of +3VLP ?

What is the voltage to ground of pin 11 (EN2) of pu301?

+3VLP (pin 16 and 17) = 3.32v
EN2 (pin 11) = 4.39v

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

This rail is critical to power the EC at U6. Confirm the same voltage is present at L4 to reach the EC VCC and VCC_IO2 pins.

Just check the voltage to ground of L2.

It is too risky to check the voltage directly on the IC.

Next, remove all power, meter in resistance mode. Check the resistance from L2 and the VCC_IO2 pin (pin 124). It should be ~0 ohms.

We want to confirm that the EC is being powered.

From the power sequence chart, this power rail is the 2nd to power up.

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

After the above checks, confirm the voltage to ground of:

EC_SMB_CK1
EC_SMB_DA1

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

This rail is critical to power the EC at U6. Confirm the same voltage is present at L4 to reach the EC VCC and VCC_IO2 pins.

Just check the voltage to ground of L2.

It is too risky to check the voltage directly on the IC.

Next, remove all power, meter in resistance mode. Check the resistance from L2 and the VCC_IO2 pin (pin 124). It should be ~0 ohms.

We want to confirm that the EC is being powered.

From the power sequence chart, this power rail is the 2nd to power up.

Pardon me but I'm not sure what L2 and L4 is on PU301. Do you mean pin 16 and 17 is the L2 or the 3V LDO voltage and L4 is the PWM voltage produced at LX pins (pin 6, 19 amd 20)? If it is, then the resistance from L2 to VCC_IO2 (pin 124) is 0.03 ohms and the voltage to ground of L2 is 3.32v when the board is powered. Likewise, all +3VLP_EC pins(22,33,96,111,and 124) on U6 have 3.3v.

The voltage at L4 is 0v which is understandable because there is no 3.3v signal at pin 12 of PU301 which is 3V_EN. 3V_EN by the way is not shorted to ground (0.5Megohms) so I don't know why it can't hold the 3.3v and goes back to 0v after a few seconds. Is this 3V_EN coming from the EC? So is my EC defective already or do we need to confirm with more tests? Thanks again.

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

After the above checks, confirm the voltage to ground of:

EC_SMB_CK1
EC_SMB_DA1

EC_SMB_CK1 = 3.3v
EC_SMB_DA1 = 3.3v

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

L4 is just north of the EC controller in the schematic.

The voltage must be 3v3 to power the EC.

This voltage rail is created by a fixed LDO inside of pu301. This rail is working since you have confirmed the same rail earlier in this thread.

Can you confirm again that the LDO volt of 3v3 is present at L4 ? If not, the EC is not being powered.

The LDO turns on this rail through a resistor based voltage divider created by the raw 19v adapter voltage.

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

L4 is just north of the EC controller in the schematic.

The voltage must be 3v3 to power the EC.

This voltage rail is created by a fixed LDO inside of pu301. This rail is working since you have confirmed the same rail earlier in this thread.

Can you confirm again that the LDO volt of 3v3 is present at L4 ? If not, the EC is not being powered.

The LDO turns on this rail through a resistor based voltage divider created by the raw 19v adapter voltage.

I confirm that there is 3.32v present at Coil L4. Sorry if I missed that coil.

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

The SMBUS readings are good.

Is the EC IC warmer to the touch? If your EC controller is the same as in the posted schematic then it indeed has firmware inside the device. There is a 8051 microcontroller embedded inside. It can be reflashed using external tools or you can purchase the EC pre-programmed from some vendors - believe there are some on Ebay. Always confirm if the firmware is suitable for your repair. Perhaps the firmware is corrupted. Replacing it is an option but again, you will need firmware to get a fresh EC component to be functional. Not my area of experience so do wait on others to comment.

Given that you do see the GPIO pins of this EC (8051 controller) perform the ON/OFF activity, perhaps some other fault is causing this enable signal to turn OFF.

Remove all power -> meter in resistance mode -> do check the resistance to ground of each inductor on the board. Perhaps some leaking cap or another part is causing too much of a current draw and the power rail(s) are shutting down from this event.

Do you see any low resistance readings on the coils to ground? The CPU / GPU (if present) are normally with a low resistance since they are low voltage rails.

[mon2]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

See attached.

What is the voltage to ground of EC_ON ? Does this voltage remain stable while you have power ?

[lgcyber]

Re: Acer Aspire 5 A514-54-37V6 No power and no RSMRST# present

See attached.

What is the voltage to ground of EC_ON ? Does this voltage remain stable while you have power ?

Very stable at 3.32V when the board is powered however when I press the power button it goes down to 0v. Hmmm. I think this should remain at 3.3v right?