LA-6582P Rev1.0 - No Power

[DanFen]

Got this Acer laptop on the bench after water liquid spill.

Schematics attached.

I could immediately see corrosion on the board (please ignore the 1 cent coin ).



That circuit is found on the schematics on Page 35. You can see the mosfet just where the corrosion is, marked as Q56.



Also, the Q56 mosfet is having almost 5V on the middle legs on both sides (and according to the datasheet, those are the gates). Datasheet for Q56.

Noob question 1: Does that make it "OK"? According to what I've researched, in order to properly test a mosfet is to actually take it out, since the measures can be affected by other components. Is this correct?

The schematics also show another mosfet on the same circuit (marked as U25) and is on the other side of the board in the same exact area. Datasheet for U25 I got 5V on 2 legs (which are next to each other), however I cannot find a way to identify which legs are these.

Noob question 2: Is there a way to identify the leg numbers without the help of a board view? I can notice a small little hole on one of the corners... what does that mean?

Some more information:
Battery connected: amber light.

[ktmmotocross]

Re: LA-6582P Rev1.0 - No Power

https://cdn.badcaps-static.com/pdfs/...3a6ef6cd1d.pdf

[onlyprinzp]

Re: LA-6582P Rev1.0 - No Power

Answer to Noob question 1:

Best way is to take the mosfet out. If you got a good heatgun (ex. heatgun station) you can take it out easy and "resolder" it back easy. If you take it out, take both middle pins on each side and put your multimeter on diod test mode, the readin should be between 0.100 and 0.500.

To find out which side is positive and which side is negative there is a number on the chip even or odd ex. 8744 -> even and you put the positive lead I think on the 2 & 3 pins , and accordingly the negative on 6&7.

If you want to keep it simple, just try it one way and the other, one reading will give you a result the other one wont give you a result.


Answer to Noob question 2:

-> Yes you can, the little dot on the chip indicates that the leg is leg No. 1


Regarding your question for the board I currently cannot make any analysis sorry for that but I hope I could help you at least a little bit


Cheers!


Edit:

I see that the mosfet Q56 is not a 8 leg mosfet, I would suggest looking on youtube how to test this one!

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Thanks so much for the information, it surely helps a lot. You taught me a couple of new things in a single post!

Yes I have a hot air station. I'll have a look later, maybe also wait for some other members to point out their view on this one.

Danke von Malta!

[diif]

Re: LA-6582P Rev1.0 - No Power

Small hole is usually pin 1. Check the data sheet to confirm.
To identify the pins on U25 should be easy. One side on all four pins will have continuity or near 0 ohm resistance. They are pins 5,6,7,8.
1, 2 and 3 are all the same again showing continuity. Leaving pin 4 on it's own.
Do tests with the power off.

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Thanks

Also I am noticing that the CPU area is hot when power is plugged in... even though it's "off". As far as I'm concerned, it's not supposed to be hot when it's off and plugged in.

I'll keep you informed about the outcome on the Mosfets.

[onlyprinzp]

Re: LA-6582P Rev1.0 - No Power

When it gets hot it usually means there is a shortage somewhere in the circuit.

Best option I like to do is to first take out power adapter, then get some freez spray and spray it on the area which gets hot. When its still liquid like, blow slightly with your mouth it will get all white frozen. Plug in the ac adapter and look at the components which gets first melted. Usually this one is in shortage.

Afterwards look what number the component has (ex. PQ102) and track it in the schematics. Another step is, if it is for example a coil that gets hot, desolder it and measure with a multimeter on each pin to ground, usually one side will be in shortage, but pay attention to the schematics.


Cheers!

[DanFen]

Re: LA-6582P Rev1.0 - No Power

I haven't tested the mosfets yet, however I will try the freeze spray as that seems the easiest and probably the most effective (at least to my eyes).

What is strange however, is that to me it seems that the CPU is getting hot. Hope it's not fried cause I left it plugged in for quite some time!! I will still give the spray freeze a shot.

Do you guys use an actual spray freeze or just a compressed air can?

[onlyprinzp]

Re: LA-6582P Rev1.0 - No Power

Check that with your CPU sounds really bad :/

I mainly use freeze spray, saw that videos on youtube about that aircan but I really dont bother cause you will just need 1 can for the future so the investment of about 10€ is not much.

Use freeze spray like this industrial ones:

http://www.ebay.co.uk/itm/FREEZE-SHO...8AAOSwTM5Y46c1

Dont use those injury medical freeze sprays, cause they could contain other substances that will stick to your motherboard. With these industrial / mechanical freeze sprays you are on a save side, especially if they have this small pipe its pretty nice to spray with it.


Cheers!

[onlyprinzp]

Re: LA-6582P Rev1.0 - No Power

One more hint, take out the CPU while you work on your motherboard, if there are parts getting hot fix those and if all seems ok, plug the CPU back in and see if it powers up correctly.


Cheers!

[DanFen]

Re: LA-6582P Rev1.0 - No Power

I tried the "simplest" thing first... got the CPU out and got myself a can of freeze air. Sprayed on the area but couldn't see any particular component that lost the freeze faster than the others.

Could be I'm not too confident with the freeze spray yet, as sometimes it just disappeared very quickly, at times it just sat there for a long time. Could also be I didn't notice, since I don't have a microscope.

So now I'm trying to check all rails starting from the DC IN. Haven't checked the mosfets mentioned earlier yet.

[DanFen]

Re: LA-6582P Rev1.0 - No Power

So I was going through the schematics and measuring voltage around the board (for hours now), and stumbled upon a High-Speed Step-Down Controller. I couldn't find much information about this, but it's model is: G5603RU1U

This particular IC is on page 42 of the schematics posted in my original post.

This is a screenshot:



Can someone please explain what it does and how I can test it out? Excuse me if I'm out of point or doing it incorrectly, but I went ahead and checked the pinouts and got these voltages:

1. 0V
2. 0V
3. 0V
4. 5V
5. 0V
6. 0V
7. 0V
8. 0V
9. 5V
10. 5V
11. 0V
12. 0V
13. 0V
14. 5V
15. 0V

Also when I connect the power switch, the power led blink randomly.

[mielta]

Re: LA-6582P Rev1.0 - No Power

Hi
First you must check U25 Pin1 where the hole is there must be 5v Present
when not check pin 5-8 this is the other side there also must 5v be present.
whwn on pin 5 is 5v and on pin1 not then you must check q56 on R935 +VSB

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Hi mielta,

U25:
Voltage on pin 1 is not present.
Voltage on pin 5 to 8 is present (5V).

So I've tested Q56 (dual n-channel). Got it out of the board to test it out properly. I never tested one, so it's the first time I'm doing it. Being it so small, made things more difficult, also my probes are kind of thick. This is how I tested in diode mode:

Drain to Source = around 830
Gate to Source / Drain = 0

Does it make it good?

Hi
First you must check U25 Pin1 where the hole is there must be 5v Present
when not check pin 5-8 this is the other side there also must 5v be present.
whwn on pin 5 is 5v and on pin1 not then you must check q56 on R935 +VSB

[mielta]

Re: LA-6582P Rev1.0 - No Power

Hi mielta,

U25:
Voltage on pin 1 is not present.
Voltage on pin 5 to 8 is present (5V).

So I've tested Q56 (dual n-channel). Got it out of the board to test it out properly. I never tested one, so it's the first time I'm doing it. Being it so small, made things more difficult, also my probes are kind of thick. This is how I tested in diode mode:

Drain to Source = around 830
Gate to Source / Drain = 0

Does it make it good?

when is it 0 than it has a short
it is dead

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Well, that's what it gave me outside the board. So - from Gate to Source and to Drain means not working. The information I was finding on the internet was confusing at times.

I'll try to find a replacement. Hope one of my donor boards has it.

Noob question: How do you manage to measure such small components? Any tips about this? It kept moving all the time!!

EDIT: None of my donor boards have that, thee closest I could find is THIS. THIS is what I have. But I don't think it can be used.

when is it 0 than it has a short
it is dead

[ktmmotocross]

Re: LA-6582P Rev1.0 - No Power

ofcourse can. the replacemeent is 3times better

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Thanks so much for that. Will try and give feedback.

Do you think replacing the capacitors next to the mosfet is better? Or shall I attempt not to replace them at first?

ofcourse can. the replacemeent is 3times better

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Replaced Q56 but no luck. Still the same.

Pin 1 on U25 is still 0V. Pins 5 to 8 are all 5V. So maybe something is wrong with the capacitors in between? The problem is they are not labelled on the board

Checked the other rails which are basically of the same design... the 3VALW to 3VS and the 1.5V to 1.5VS and it's the same with them, obviously with the respective voltages. So I have a feeling that the 5V we're working on is fine. If this is the case, then the fault is on some other circuit?

So if we go back to the symptoms, the power LED just turns on and off randomly for a split second. The area we worked on is where we've seen the water spill.

[DanFen]

Re: LA-6582P Rev1.0 - No Power

Did some further checks, and it seems that now the problem is on the 1.5V rail. It's just I can't seem to find out how to trace the prob.

I ended up on the PU22 (mentioned above as: G5603RU1U), and it seems it has the 5V on the 5V inputs and outputs, but the 1.5V is missing. Replaced it but still the same.