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Laptop Short causing weird symptoms

Posty07

Jul 26, 2022
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Hi All,

I have unfortunately damaged my laptop while replacing the thermal paste. I forgot to remove the battery and accidentally shorted, and completely fried, a component.

I've done some digging and it appears to be a ferrite bead, 80ohm impedance (specifically fbma-l11-800lma50t)

I bypassed this with solder to get the laptop to turn back on, but now if I stress the graphics card, or even start a game, the power and battery lights start to flash and it eventually just turns off after a few seconds.

I've ordered a replacement ferrite bead, but I'm worried that it's actually something else that's damaged. Would a simple ferrite bead cause this to happen, or should I be digging around further?

Thanks
Adam
 

Posty07

Jul 26, 2022
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Seems to me you haven't fixed the first issue......
I don't think it's temp issue as watching the temps they don't go above 70, but the laptop doesn't seem to stay on long enough to overheat. I was only replacing the thermal paste to try to get it a little cooler. There weren't any reliability issues beforehand.
 

kellys_eye

Jun 25, 2010
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There weren't any reliability issues beforehand.
That's my point.

If it worked before you 'played' with it then it's what YOU did that's making it problematic now. The odd's on something else just randomly cropping up is miniscule.
 

Posty07

Jul 26, 2022
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Well yes, I know that.. I'm asking if the component I shorted could be the issue, or if it's more likely to have affected more than just that component.

In other words, will that ferrite bead actually cause problems like that, or is it more likely that something else is damaged like the GPU?
 

Martaine2005

May 12, 2015
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I bypassed this with solder to get the laptop to turn back on
Perhaps a picture is worth a thousand words!.
Never bypass something with solder if you don’t know what it is or what you are doing. Almost guaranteed to destroy more.


Martin
 

Posty07

Jul 26, 2022
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Hi Martin,
I'll get a picture tonight when I get home.

I did think with it being a ferrite bead that they are basically close circuit anyway.. but I may be very wrong.

Cheers
 

Posty07

Jul 26, 2022
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Picture attached, the blob of solder is where I've bridged, albeit pretty badly..
 

Martaine2005

May 12, 2015
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Just out of interest, remove the blob of solder and check the capacitors in that area for a short to ground.


Martin
 

Posty07

Jul 26, 2022
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Just checked them, both are ok, or at least not shorted.

Picture resized
Compress_20220726_202454_4576.jpg
 

kellys_eye

Jun 25, 2010
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Generally, a ferrite bead (slipped over a shorting link) will have little-to-no effect on circuit operation in most cases BUT they are there for a reason - blocking hf noise from entering the power lines.
Simplest answer would be to replace the ferrite with something similar - it doesn't have to be identical (size) but the impedance should be close to the nominal.
Many modern circuit boards have these fitted so a scrap circuit board would be a good place to find something that might fit the need. Sites like Farnell also carry such components so have a browse and see what's on offer if you don't have any circuit boards to hand. The key search words are 'EMC suppression components'.
 

73's de Edd

Aug 21, 2015
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Sir Posty07 . . . . .

To err is human
. . . . . . .
and BOY ! ! ! . . . . . are you human !

The immediate area in which you are kadiddlewhomping around in, is being in the circuit domain of the . . . . . sub power supply . . . . e.g.

JW5068 . . . . . Power Supply Circuit

https://www.joulwatt.com/Upload/file/201812/20181217172206_3125.pdf

It takes a portion of the FULL laptop power supply voltage and then down converts that full voltage
to a HEFTY 8 amp or more, as a separate lower voltage supply.

HOW TO READ THE FOIL . . . .

Bottom right corner, I see only see the visible P of probably what is a PLxxx designation.
Trace that lighter blue resist covered foil, downward and to over to the left , where it widens and initially passes to the other board sides foil thru 7 or so via holes and then two brown 0.1 ufd monolithic ceramic capacitors ***** provide bypass into the other foil pad just above them, which is a ground plane with its 9 or so vias to the boards other side and that ground plane also makes a connection into the pins 7-8 grounds of the JW5068.
***** ( The soldering installation of those caps closest end caps is APPALLING ! )

Now, in continuing with our light blue main full power trace to the left towards the PU501 area, it then connects with another minor ceramic bypass capacitor and has vacant pads above it for another, and FINALLY gets to its destination of the main power input pins of the JW5068 as 2-3-4-and 5.

Now what I would REALLY want to see, is the removal of ALL of that solder, BLOB to see what is being underneath it.
BECAUSE I see no need for there being a ferrite bead in circuit there unless they were wanting to be taking some of this FULL supply voltage off from this power trace foil and feeding it thru a ferrite bead for isolated EMI and RFI suppresion, to then pass that power off to feed another completely different circuit..
If so, one end of the beads end connector would be connected to this power buss foil area, while the OTHER connector end would have to be connected into a cut out and isolated pad, that uses a via to pass thru to the other board side. as I am seeing no routing out foil or an associated via being on this side of the board . . . . I am just seeing your very beeeeeeg solder / island. . . . . and some errant tiny solder droplets / splashes
Your small ferrite bead isolator should look like this . . . .

upload_2022-7-27_12-7-18.png

Now, can you initially get a well tinned soldering iron and invert the board an look up to that solder island and place the tip to it and let it melt and let gravity drain that solder down and onto your tip . . . doing it multiple times until minimal solder is left, and then use rosin flux and wick to get all of the remaining solder build up.
Follow up with an acid brush soaked in alcohol for a flux clean up.
Now . . . is there any foil routed out for isolation of the output end of this ferrite bead isolator ?

SUB SUPPLY OPERATION . . . . .


What you might check out after your power up of the unit, is the voltage output of that JW5068 supply and monitor it with a voltmeter connected to the aforementioned ground plane and the + meter probe going to either the pin 14 of
JW5068 . . . or access might be made easier at the right end of the L1 ringing inductor, as is being the large, gray rectangular pot core at the 2 o'clock position from the JW5068.
OR, I think that the filter capacitors for that supply are being the 3+ large monolithic block, high capacitance yellow ceramic capacitors, being located just above it.

Is the voltage being stable, BTW . . . what voltage level is it being ? or does it tie in to a related change just before the unit goes down ?

ON PAGE RE-REFERENCING TO PRE HOSTED BOARD IMAGE . . . . .

AM-JKLUZIaoG9JxHgJut8EPCmgqzMTgMLAtWtUhaWEP0AXzuwcYoaM95wgJKYaqA0x9-zJ9gpPt9tX5z1boYZdiu0IazK-DfDHEIOHzTKicdMhnOSd7vghU6FLbmgq1vivikJuIhPcO55eRQfwFVgquhL7qdDg=w728-h969-no



I've done some digging and it appears to be a ferrite bead, 80ohm impedance (specifically fbma-l11-800lma50t)

Care to SHARE info . . . . . as you haven't even given us the damn BRAND as well as its MODEL . . . also, possibly even a link to its SVC manual if having already found that specific part #.


Thaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaasit . . . . . . . . . . .

73's de Edd . . . . .

line.gif

I used to think I was indecisive. . . . . . . . . . . . . . . .but now. . . . . . . . . . . . . . . . . .I’m not so sure.


.
.
 

Posty07

Jul 26, 2022
8
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Jul 26, 2022
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Thank you both for the detailed replies.
I'm away from tomorrow so I won't be able to answer most of those questions till next week, but I will!
I found the ferrite bead model as it's PL115 within this document https://www.scribd.com/document/495...H50F-EH51F-EH5VF-EH70F-Compal-LA-H501P-Rev-1A

Unfortunately you have to sign up to Scribd to see the full thing which I did.. just have to remember to cancel the subscription!

Laptop brand is Acer, model AN515-55, with the gtx1660 GPU and i5-10300h

I did try removing the solder blob completely and the laptop did not turn on, so I would guess it's quite important.

I managed to find the exact model of bead on AliExpress which was cheaper than buying a pack from farnell in my own country :(
 
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