Identifying and replacing laptop smd component

Thread Starter

Kaseftamjid

Joined Oct 4, 2019
5
IMG_20191005_084325.jpg
(Hey people, first post here, look forward to contribute to the community )

Ill go straight to the problem. I have a *really* old asus x45u laptop without batteries. The old battery gave up but i still have the original circuit from it. So last night i was trying to connect a 12v 5A lead acid battery to the battery circuit, as it calls for a series parallel configuration (12v-6v-4v-Gnd). I would have used 2 separate 18650 battery to provide 4v and 6v. But i accidentally connected the circuits gnd to battery 12v+ and 12v to gnd of battery. So my laptop made a small crickle(?) kinda sound and didnt turn on anymore from the charger. I opened up the motherboard and saw a small smd component with burns around it( see picture) the burnt component while in the circuit measures 13.6 ohm, but i found another similar looking part on the board and it measure .5 ohm. Few google searches turned up that it was some sort of link( am i mistaken?).

So my question is
1. Can i replace/fix the burnt part? I mean if it is a link then cant i just remove the component and solder the 2 pins together?
2. What i originally tried to do ( 12v battery and 2 18650 battery to provide power for the circuit) would it work?
3.imagining it works, can the laptop battery circuit charge the lead acid battery? (4.2*3=12.6v?)
 

Tonyr1084

Joined Sep 24, 2015
3,578
If each end has metallization on all four sides and the face (five sides) then it's either a capacitor or (more likely) an inductor. Given the color I would lean towards an inductor - but that is as much as a guess as how many pennies I have in a jar upstairs. It's just a guess. Resistors have metallization on the top and bottom as well as the face (three sides).

You said you have the schematic, right? And "Size" means nothing. I have been soldering 1 mm by 2 mm parts for the last four weeks. You don't expect to find them if you drop them. Once gone they're gone forever. The 1 by 2 is called an 0201 part, referencing its size. The next larger ones are 0402. From there they get bigger and bigger. But size means nothing. Except their voltage rating or current capabilities or wattages.
 

Thread Starter

Kaseftamjid

Joined Oct 4, 2019
5
If each end has metallization on all four sides and the face (five sides) then it's either a capacitor or (more likely) an inductor. Given the color I would lean towards an inductor - but that is as much as a guess as how many pennies I have in a jar upstairs. It's just a guess. Resistors have metallization on the top and bottom as well as the face (three sides).

You said you have the schematic, right? And "Size" means nothing. I have been soldering 1 mm by 2 mm parts for the last four weeks. You don't expect to find them if you drop them. Once gone they're gone forever. The 1 by 2 is called an 0201 part, referencing its size. The next larger ones are 0402. From there they get bigger and bigger. But size means nothing. Except their voltage rating or current capabilities or wattages.
I meant the pcb from inside the battery, not the diagram/schematic of the motherboard. Few google searches confuse me even more, as both of the 0201 capacitor inductor look same. But educated guesses would point to a capacitor as the part blew on reverse voltage(?) but there is also the fact that these small caps should be ceramic, not electrolytic.
Can you help me make an educated guess on what i could replace it with? I have a lot of spare circuits lying around but i didnt find ONE part that would even match the size ( aside from some capactors)

I just checked the battery pcb and it looks like that the burnt part is connected to the - - pin of the battery circuit.
 

Wolframore

Joined Jan 21, 2019
1,254
Those are bypass filter caps for stabilizing the charging regulation for the battery. You should look up the regulator chip and do some research on the recommended values. Without knowing more it would be difficult to guess.

The inductor for your switching supply is on the left next to the fuse. The large cap is electrolytic and next to the inductor to supply the regulator.

It also looks like there are a lot of unpopulated parts. Is that normal or did you remove components?
 

Tonyr1084

Joined Sep 24, 2015
3,578
If they are caps they are most certainly NOT electrolytic. If they were they'd have a clear indication as to which end is the positive. As for value - - - guessing is the best way to destroy more parts.

On that note - - - it's possible that what ever took the (lets call them) caps out - it's a good possibility other components have been hurt, damaged or blown.

It's almost impossible to tell from the picture if there are designations for the components. Silkscreening. Usually white; letters and numbers can give a clue to what belongs there. For instance; C1 is a capacitor. Indicated by the "C". The "1" would represent the part as found on a bill of materials (BOM). There, on the BOM you'll find the capacitors value and voltage. A marking beginning with "L" typically suggests an inductor. D = Diode, R = Resistor, Q typically refers to a transistor and U typically represents an integrated chip. Not all companies adhere to this standard but most do. Some don't even use silkscreening to indicate parts.

@Wolframore the unpopulated pads look like they were solder-pasted at assembly, but no components have ever been placed there. Indicated by the rounded dome shape of the solder. Usually when a part is removed the solder will be shifted to one side or the other. USUALLY. Or other signs of disturbed solder. I don't think anything has been removed. Not yet. But I still say those components in question COULD be inductors, as inductors are also used to resist current fluctuations. However, they certainly don't LOOK like ceramic caps. Those are usually lighter in color than the typical SMT Cap. But you can't go on appearance alone.
 

Thread Starter

Kaseftamjid

Joined Oct 4, 2019
5
I did a little more digging and found these LMK212BJ226MG-T capacitors which fit the visual bill. They are 0201 and rated 10v22uf. As for the BOM i couldn’t find it online as my laptop is like *really* old. (Asus x45u , bobcat processor ). Aren’t they supposed to be confidential ?? I mean designer to manufacturer and not the public? And yes, i didnt remove any component. I'm just hoping that nothing else got hurt or it (maybe) couldve been the only thing that got in the way of a full fledged short circuit and blew.

As for the regulator, i cant find anything like that, more accurately i don't know what to look for, but surely there aren’t any linear regulators here. Most of the unpopulated pads seems to refer to capacitors, and some of them are positioned in such places which indicate filtering purposes.

Another question on my mind, is every electronics meant to show signs of destruction? I mean if these parts are so close and if they are the battery control circuit, then why isnt my laptop turning on from the wall charger? I cant find anything that seems to be damaged. This laptop has many good memories... I cant afford to just throw it away
 

Wolframore

Joined Jan 21, 2019
1,254
Many chips can’t take much more than 5v some only 1.7-3.3v. If you somehow shorted you may have killed the chip. If somehow the chip has managed to survive you have to check power. I would start checking things with a multimeter. Start with the little green fuse.

You can pull your hard drive and put it into an external container to get your files from that lap top. Nothing lasts forever but if you’ve been trying to modify it, it’s your fault. Might just be a learning experience.

I didn’t say linear regulator. I said switching. They do that to be more efficient and make batteries last longer while making less heat.
 

Tonyr1084

Joined Sep 24, 2015
3,578
Those caps in the red circle are NOT 0201 components. 0201s are so small they are smaller than a flake of pepper. Or as small. You virtually need a microscope to work on them. I know, I spent four weeks in Idaho doing rework on those 0201 components. 0201 is the smallest I know of. If you look at the cap just to the left of the two circled, it is smaller. Yet it is not the smallest in the picture. There's a chip on the lower right side of the picture. Adjacent that is what appears to be an 0402 resistor. Or maybe it's an inductor or a cap. There's not enough resolution on the picture for me to make a better guess. But it is not even the smallest out there.

I brought an 0201 home with me just to show my wife how small the devices can be. I'd take a picture of it but it's so small seeing it in the photograph would be unlikely with my cell phone. But I'll give it a try and see if I can manage a shot of a true 0201 component.
 

Wolframore

Joined Jan 21, 2019
1,254
They look more like 0805 or 1206. For comparison that 1 Ohm resistor on the top left is 1206.
 

Tonyr1084

Joined Sep 24, 2015
3,578
Smaller than a single digit on a dime, an 0201, shown inside the box, the arrow pointing at a small black object with metalized ends - the picture is the best I can do with a cell phone and a 10X eye loupe. This is a resistor. I believe the value to be 15KΩ. Have no plans on using it. Just brought it home because it came off a board as defective.

What you have is larger than the entire date on a dime.

0201A.png
 
Last edited:

Thread Starter

Kaseftamjid

Joined Oct 4, 2019
5
Yep... In my opinion you cant learn without destroying stuff, its just a matter of whose stuff its gonna be. I was under the impression 0201's were so much bigger!! Someone was right! You never expect to find them if you lost em, i learned that last night while trying to remove one from a dead board(other broken stuff).

I did pull my hard drive and put it in another dell laptop. Trust me, no one hates dell more than i do right now. I was using the original charger as a power supply for another project and the one-wire ic inside silently died in programming mode. I think i should open a new thread about this matter, please stay with me over there too :)
 

Tonyr1084

Joined Sep 24, 2015
3,578
Trust me, no one hates dell more than i do right now.
LOL! I appreciate your pain.

If you want a good reliable system you need to get away from those mass produced money pits they falsely claim to be "Reliable Computer Systems". (RCS) It may be more expensive to have a computer custom built (or to build one yourself) but the investment is far above what you can expect from an RCS on the open market.

Incidentally, there IS a new use for your old RCS - that of a door stop or a window prop (if your window won't stay open).

WARNING: Old hard drives are used and worn. They WILL fail sooner than you might think. I have several used hard drives that rest quietly on a shelf. They contain backed up materials just for when my current HD fails.
 

seanstevens

Joined Sep 22, 2009
66
I am not sure but I would guess the SMD 'caps' are not caps but possibly either a ferrite or inductor in series with power input and if they are gone there will most likely be other components that have been damaged.
If that is the case, and you have identified another component that looks identical and measures 0.5 Ohm, then it is most likely a ferrite/inductor. I it was me I would short the destroyed components and maybe use a power supply that you could limit its current and power up to see what else has failed. Of course this is risky doing that but thats me. If one side of the damaged component is power in then the other side of it is most likely almost shorted to ground, that might be a starting point to to try to remove that short which could be in any of the components down stream.
 

Tonyr1084

Joined Sep 24, 2015
3,578
I am not sure but I would guess the SMD 'caps' are not caps but possibly either a ferrite or inductor in series with power input and if they are gone there will most likely be other components that have been damaged.
Yeah, my first thought, based on appearance, was the same - an inductor. Pretty much said the same things in posts #2 & #5. Glad someone else sees the same things I see. Thanks.
 
Top