Acer nitro 515 no power, missing 3ALW

[ca3cooh]

Pardon me, complete noob here.
I have a acer nitro with schematic attached
My laptop died after upgrading win 10, it become unresponsive sometime, afteri force shutdown it, sometime it boot, sometime windows did not load, and finally it did not turn on at all.

My measurement is as follow :
3vlp and 5valw missing
VCC EC missing
tried injecting power to JPB1, it measure 500mA on 3v.
5valw rail ok no short, tried to turn it on and it works ok.
First standard attempt usually to flash its bios, but bios is not on, pin 8 on UH2 is low, so i think i can ignore it, or should i flash it first ? (I try to avoid this, because i dont have other laptop to do it, this is my only driver currently)

My suspect is 3VLP to power ec is down, but i dont know which component supply this voltage. Could somebody point it to me ?
Tried unplug its rtc batt, no luck
If i connect its battery, no 12v present, only 19.5v if i plug it. Battery condition is good, it measure 2Hour before this laptop died.
Voltage on sw on button is 1.2v

Any insight is greatly appreciated. Thankyoui

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

Do not just inject voltages onto the logic board. Not at first till more is known on the operation of the power rails.

See attached.

Meter in DC voltage mode (any setting 20V or higher is ok).

Red meter lead on each point of the attached schematic. Black lead to ground.

Check and post the voltage reading for each requested mosfet location.

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

Do not just inject voltages onto the logic board. Not at first till more is known on the operation of the power rails.

noted, thankyou sir.

All of them were on 20V pluged in.

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

With no battery, pin 4 (gate) of each mosfet is at 20v when adapter is attached?

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

yes, both gates were 20v

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

Ok. Remove all power. meter in resistance mode (200 ohms is ok).

Check and post the resistance readings for the following mosfets.

1) resistance between Drain (pin 5-6-7-8) & Source (pin 1-2-3) of PQ310 ?

2) resistance between Drain (pin 5-6-7-8) & Gate (pin 4) of PQ310 ?

3) resistance between Gate (pin 4) and Source (pin 1-2-3) of PQ310 ?

Then repeat the same testing for PQ311:

4) resistance between Drain (pin 5-6-7-8) & Source (pin 1-2-3) of PQ311 ?

5) resistance between Drain (pin 5-6-7-8) & Gate (pin 4) of PQ311 ?

6) resistance between Gate (pin 4) and Source (pin 1-2-3) of PQ311 ?

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

Found short on 3VALW rail, proceed to remove inductor PL402 praying to god that the short were on PU401 side, but to no avail.
Short were on 3VALW rail, reading on multimeter were 0v on diode mode.
Is it save to say that this mainboard is toasted ?

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

Next, check if the ALWP rails are being enabled by the logic board.

1) Confirm the voltage readings as per attached diagram for the +3VALWP rail.

2) Then check the same for the +5VALWP rail.

3) Remove all power. Meter in resistance mode. 200 ohm setting is ok.

a) check and post the resistance to ground of inductor (coil) PL402, pin #2. Checking if there is an excessive load = very low resistance on the rail that will cause the switching regulator to shut off.

b) check and post the resistance to ground of inductor (coil) PL404, pin #2.

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

Oh - just saw your post on the short.

1) Remove PL402 as you are doing already. The short could very well be in the noted area as per attached diagram.

Review the attached. Then proceed to hot air remove each cap (22uf). This is only a random guess but can start here if there was no liquid spill, etc.

If you remove the caps - just leave them off the board for now and keep track of them. They are not polarized so can go back in any direction.

2) For starters, remove these caps and then check the resistance to ground of PL402, pin #2 again.


update - the logic board offers solder blobs as shorts Good thing and we can use it to isolate the shorting part.

See attached.

3) Remove the solder block @ '1' location and then check the resistance to ground again. Is the short still there ?

For now - do not remove the solder block @ '2' of the attached schematic.

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

those caps were ok, proceed to remove PJ401 as you suggested, and the short side were on pin 2 (3VALW rail)

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

ok - place those caps back onto the board.

Each '+3VALW' label appears to be followed with more solder blobs.

Consider to locate each solder blob and remove it. Then after each solder blob removal, check the resistance again. If the short is still present, solder the blob back onto the board.

Do not power up till we locate the reason for the short.

Can you confirm your meter setting? Are you in the lowest resistance setting of your meter (200 ohms is ok) ?

With 0.00 ohms, that is a direct short to ground.

Be sure that your meter (red probe) is on the voltage rail being tested & black to a good ground. No power to the logic board with the resistance checks.


Q: When you removed the solder blob PJ401 - the +3VALWP rail was no longer shorted ? So PL402, pin #2 was showing a high resistance to ground ? Please confirm this detail.

Consider to remove the solder blob PJ7108 and check the resistance again.

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

i calibrate my meter with both known voltage and resistance, and its showing correct value.
Proceed to disconnect junctions related to 3VALW and no short persist on receiving pin.
Connection that i removed were PJ1402, PJ7105, and PJ7108.
just For thorough checking, i remove all of the blob on pins above, but 3VALW stil short.

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

Confirm in resistance mode (200 ohm scale), the resistance reading to ground on +3VALW. Is it 0 ohms?

Respectively, when you remove the solder blob @ PJ401, then PJ401, pin # 1 is no longer a short to ground ? What is the resistance to ground with the PJ401 solder blob removed ?

There are many parts that make use of the +3vALW rail and each has to be inspected to search for the offending part.

Post the resistance values.

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

Yes sir, if i remove PJ401, pin 1 no longer short.

Background story,

I buy this board on dead condition, further checking i found the controller ic for VCC_CORE is faulty. After i replace the ic it turn on ok, albeit i cannot uses its IntelHD vga, i can only uses its dedicated NVIDIA vga.

Just to make everything save, i modify this device so it uses 2 more additional 5v fan with buck converter from 20v.

I used buck converter to stepdown 20v to 5v so the additional fans did not put more load to my 5v rail on my mainboard, but it only use 3VALW rail trough 1k resistor to turn the said buck on.

I used it for almost a year with heavy usage and thankfully no problem occur.

Couple a days ago, i open this device to clean the dust that usually buildup. After asembly, i used it couple of time and updating its windwos with no problem until its demise.

And just now, after doing all that you suggested, i check my buck circuit again.
And voila, my fool self found that i did not secure wrap the signal wire to my buck and it barely touches 20v.

Sad to say that my 3VALW apparantly connected to 20v because of my lack of carefulnes, and it does throws my hope to the bin.


TLDR : 3VALW connected to 20V


@mon2 thankyou kindly for your time, i'm gratefull for your patience assistance, Terimakasih banyak.

If you think there is hope, i would glad to hear it but right now im kinda lost hope.

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

I think the brief short to 20V and the 3VALW line may be a deal breaker.

You can check the resistance to ground on this rail. With the blob @ PJ401 removed, you can consider to inject a 1v Dc power supply onto PJ401, pin # 2. Then check the current draw of your power supply. Of course look for any part that may be heating up.

Thermal camera helps but we do not own one yet ourselves. Using IPA (alcohol) across the parts works very well. Whichever the part is heating up will cause the IPA to evaporate and/or mist away.

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

You can check the resistance to ground on this rail. With the blob @ PJ401 removed, you can consider to inject a 1v Dc power supply onto PJ401, pin # 2. Then check the current draw of your power supply. Of course look for any part that may be heating up.

Will do sir, right now my psu only abble to supply 1.2v on 1A, not enough to make any significant heat. I will get back to you if i can get my hands on more powerfull PSU

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

have my hand on 0.8v PSU

sad news its PCH thats heating up

[mon2]

Re: Acer nitro 515 no power, missing 3ALW

Yeah then game over I am afraid. From the assorted posts on the forum, the very large BGA package of the PCH is not easy to replace. We brought in a special tool for this and it costs more than my car. Has a laser pointer and reflow profiling on this table with HD cameras. For the same reason we are trying to make the proper floor space for this quite large BGA rework station before we remove out of its crate. Then it should be possible to replace CPU / PCH, etc.

I know that we worked with a company in Malaysia that is wicked and can replace SMD BGA ram devices on macbooks / imacs and can even swap out CPU. We just do not have that experience yet. It may be just a lower cost to treat this board as a donor for future repairs. We tried

[ca3cooh]

Re: Acer nitro 515 no power, missing 3ALW

Yeah, thanks again for your kind reply.