Acer N19C1 / FH5LA LA-J801P Board wont turn on

[alphaedrum]

Hi, first of all Im still learning and any advice is very welcomed. Also have me a bit of patience with all of this please and sorry for the butchered english.


I have very, very basic electronic knowledge but I decided to learn a bit with this dead board since I got it for free so there is nothing to lose if it goes south plus I can learn in the process.

The laptop suddenly stopped turning on, and the ownder didnt cared enough to get it fixed. Also the charging led doesnt turn on either.

This is what I have already done with the board:
After doing some troubleshooting I found what I believed to be a short on a dual mosfet (PQZ1). When I removed the mosfet the short dissapeared so I proceeded to get a replacement thinking that was the only issue.

I soldered back the replacement but sadly it still wont turn on.

The only other thing I believe it was donde with the board was some internal cleaning by another person.




After that I checked again and 19v is present so I used the boardview to check if either 3v or 5v were having issues and certainly both were not present.


Pin 14 (+3VALWP) of PU301 (SY8286BRAC) outputs nothing, yet pin 2 to 5 receive correctly 19v. It doesnt turn hot or anything.


On the other side, pin 14 (+5VALWP) of PU501 (SY8288CRAC) outputs 1.8v and it gets very hot if I touch it. It also receives correctly 19v fron pin 2 to 5 as expected.


My lack of knowledge says that those two ICs are damaged but since Im not really experienced I could be missing something else. Any help, guidance of how to keep troubleshooting is welcomed.

Thanks in advance.


I checked pin by pin on both ICs and these are the readings:

PU501:

Pin
1 (BST_5V) reads nothing
2,3,4,5 (+19VB_5V) reads 19v
6,19,20 (LX_5V) reads 1.87v
7, 8 GND
9 SPOK_5V reads nothing
10 not connected
11 (ENLDO_5V) reads 3.86v
12 (5V_3V_EN) reads nothing
13 (5V_FB) reads 0.22v
14 (+5VALWP) reads 1.87v
15 (+5VLP) reads 4.98v
16,17 (VCC_5V) reads 2.7v
18 GND

PU301
Pin
1 (BST_3V) reads nothing
2,3,4,5 (+19VB_3V) reads 19v
6,19,20 (LX_3V) reads nothing
7,8 GND
9 (SPOK_3V) reads nothing
10 not connected
11 (ENLDO_3V) reads 3.86v
12 (3V_EN) reads nothing
13 (3V_FB) reads .01v
14 (+3VALWP) reads nothing
15 not connected
16,17 (+3VLP) reads nothing
18 GND

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

What is the resistance on PU301,pin17 and PU501,pin15?? Remove coil PL502 and check voltage on PU501,pin14 again.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

What is the resistance on PU301,pin17 and PU501,pin15?? Remove coil PL502 and check voltage on PU501,pin14 again.

Hi, thanks for answering.

PU301, pin 17 to ground, my multimeter says 008 on the 2000 ohm setting and 4.4 on the 200 ohm setting.

PU501, pin 15 to ground, my multimeter starts at around 800 and hovers around 1270 on the 2000k setting.

Removing that coil with the tools I have atm is going to be a bit hard, but Ill give it a try and report back after doing those tests.


EDIT

It took me a while but I managed to remove the coil. PU501 pin 14 reads 0v now after removing PL502.

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Going by your readings, you have short on +3VLP(popularly called LDO). Remove PU301 and re check the resistance on pin17. If still showing short, you need to inject voltage on pin17 . Start with 1V/1A and gradually increase the amp but dont go for higher voltage. You'll need a dc supply to do this.Most likely its the KBC shorted and under worst case scenario both kbc+pch shorted.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Thanks again for answering.

Its midnight over here so I will give it a try tomorrow and then report back.

Just one question, If pin17 its still shorted after removing PU301 and by injecting voltage the KBC should get hot if its shorted, right?

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Right

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Right

Im back and I managed to remove PU301.

Pin 17 stays the same, reading 008 at 2000 ohm setting and 06.4 on the 200 ohm setting.

I proceeded to inject voltage on pin 17. It keeps providing 1v/0.25A and barely increases the amp consumption if I increase the amperage (by like .01 or .02 per 1 A). This with either the PU301 installed or removed, but with the coil PL502 still removed.

So, the KBC didnt got any hot at all.

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

How many amps you injected?? Go upto 5A while keeping the voltage at 1V. However, if still you cant feel any hot components then do the following.

01.First check all high side mosfets for shorting.
02.Look for any corroded/burnt controller
03.Proceed to increase voltage on pin17 of pu301 gradually and go upto max 3V/5A
04.Step 03 should be done if and only if step 01/02 doesnt give any wrong indication.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

I actually went up to 5A in my tests, remaining at 1V as you said and it drew up to 1v/0.27A when injecting. Going to doublecheck again today just to be sure.

About the next part...

01. Since Im quite new, I havent heard the term, but I will investigate a bit and give it a try. Im starting to consider purchasing another multimeter because the one I have atm dont "beeps" while checking continuity.
02. I already inspected for any corroded/burn parts on the board and its clean. Will doublecheck thought.
03. Ok ok

Ill come back later today with what I found. Thanks again.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Testing with 1V 5A, the draw increased to .29A but still couldn't find any hot spot at all.

I only managed to find 3 mosfets on the whole board. PQZ1 (the one I replaced that was causing the original short), PQZ2 and PQG3.

Testing the pins, either pin 1,2 and 6 show no resistance to ground. Pin 3,4 and 5 as they are connected to ground directly they do show resistance to ground as expected.

Pin 7 in all of them show resistance to ground too, by testing with their respective coils (PLZ4, PLZ3 and PLG1), and back to what I believe are tantalum capacitors (PCZ18 and PCG30) they all show resistance on their pins. Not sure if that is normal to be honest.

I looked again for burn/corroded parts and couldnt find anything.

Since I found resistance there I decided to delay the part 3 of your instructions until you confirmed me that I could proceed. Also to be safe if I need to proceed, should I inject voltage with PU301 and the coil PL502 installed or without them?

Thanks again.

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

What is the exact resistance on pin7 of PQZ1?? We do expect a low resistance here as this is part of cpu core circuit and is a low voltage,high current rail. An exact reading in Ohms mode is needed. Set your meter in 200 Ohms scale and measure pin7 resistance..

Btw, consumption at 0.29A(290mA) does indicate a short. Did you injected 1V/5A for long time say 10-15 mins?? Look very carefully on two areas of suspicion-Small die on SOC(PCH part) and KBC. Do inject voltage as specified earlier but for long duration and check again after 15 mins. A 10A dc supply would have made it a bit easier.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

The resistance on all of their pin7's is the same 1.4 in 200 ohm scale, which is the same than ground with ground. Guess thats okay then.

I injected it like 5 minutes tops, so Im going to try tomorrow for a longer period of time.

I forgot to mention it but the power supply Im currently using for this can go up to 12A.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Okay, so I tried the 15 minutes at 1V/5A and certainly I noticed that the KBC got a little hot. Couldnt notice anything different on the small die but I checked it by finger since I dont have a termometer or anything to check more reliably.

[mon2]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

You can pour some IPA (alcohol from pharmacy store) on the part. Heat will cause the alcohol to evaporate or mist away.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

You can pour some IPA (alcohol from pharmacy store) on the part. Heat will cause the alcohol to evaporate or mist away.

Oh yeah, I know about that, but sadly I didnt had any IPA on hand today. I will get some tomorrow and try again just to be sure.

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Now, inject 1V/10A for 5 mins or more and be double sure its kbc which is getting hot. If you are sure, then remove the kbc,clean the solder pads and then re-measure resistance on PU301/501 pins described earlier.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

I left it for 10 minutes at 1V/10A with a couple of drops of IPA on both the KBC and on the PCH but on neither the IPA evaporated noticeably quick.

Maybe I imaginated it yesterday, since there is a heatwave around here and pretty much anything feels kinda hot at touch.

Something that I noticed is that the IPA does evaporate from the KBC if I plug the charger after like 20 seconds. I tried to rule out the current hot temperature but if its unplugged it will stay there a bit longer.

[mcplslg123]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

So, you youself is confused?? We dont have the board in front of us. i dont recommend removing /swapping parts unless sure about the fault.However, going by experience, kbc is faulty, So if you want you can de solder it and see if the resistance jumps or not. Else you can wait for other experts advice.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

I was too busy today, so I will attempt the removal of the KBC tomorrow and will come back with the readings.

[alphaedrum]

Re: Acer N19C1 / FH5LA LA-J801P Board wont turn on

Thanks for having me patience. It took me a while but I finally managed to remove it.

PU301 pin 17, 0 resistance
PU501 pin 15, 0 resistance
PU501 pin 14, still reads as 1.8v when plugged to the charger

I guess sadly thats the end of the road for me I guess. The replacement part its quite expensive for me (20 USD plus the waiting time) and I dont have any spare parts on the damaged boards I own to cannibalize it. Also, I might be wrong but didnt that part needs to be flashed with a specific firmware for this board in order to work? or I mistook it with a different part?

why the heck the one I need (kb9052qd) costs almost 10 times more than other KBC like an KB9022qd, for me at least.

Again, thanks for all the help toubleshooting this.