Latop surface component breaks off

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Hi,

I disassembled a laptop to replace the power jack and during the
process dislodged a [tiny] surface component.  

It doesnt look like it has leads of any sort. It's beige. A resistor?
A cap? Need help. It's off the board and I'm hoping it's
unidirectional and that it can be soldered back and all will be well.

I'd appreciate any comments.

looking.

Re: Latop surface component breaks off

Quoted text here. Click to load it

A picture would help. However, from the description (tiny, beige) I'd
guess that it is a non-polarized capacitor similar to
<http://en.wikipedia.org/wiki/Ceramic_capacitor#Multi-layer_ceramic_capacitors_.28MLCC_chips.29
and you can safely replace it in either orientation. Remove all of the
remaining solder from one pad (so that it's smooth) then flux and tack
the cap to the opposite pad. When it looks like it's oriented right,
tack down the other pad.

Re: Latop surface component breaks off
wrote:

Quoted text here. Click to load it


Thanks for replying.  That's about what I found out and I got the unit
back up, albeit without apparent battery functionality, and a slight
off color smell. Powered down after a few minutes but on the second
boot-up, the box was on breifly and then went blank after a pop. I
disassembled back to the MB and the dislodged capacitor I had soldered
back on had had some malfunctrion and was no longer soldered on.

I know it's a capacitor per writing on the MB, PC108. It's in a group
of 3 and after soldering the pc back and reassembling the laptop, I
check omhs across each of the 3 caps and all read about 113-116 on a
VOM.  

Trying to be brief: it's tight in there particularly since the power
jack has been resoldered, but I'm still hopeful about the repair. The
unit did function after try 1, so I think that  if I can get the cap
back in there, there's a good chance of success as caps do fail,
people replace them and th eunits function even if there is a pop when
they fail?

In the back of my mind, I still wonder about the polarity issue though
I can't see how to tell one side from the other. Unless I'm using
magnification? Am I correct to be concerned? Have I provide enough
info to determine?  

From where I am, I need a replacement cap. Can I go to the stockpile
of old boards and eyeball a replacement? Or is this the kind of repair
that I might be able to get done a shop that might bail my sorry butt
out?

Lastly, it's hard to desolder. Do you have a toll recommendation?

I just checked out the link, it is an MLCC. I haven't finished reading
yet, Would this component be heat damaged in a bad soldering job?

Thanks for listening.




Re: Latop surface component breaks off

Quoted text here. Click to load it

The easiest way to remove them is either a hot air station or a pair
of soldering tweezers, which are like a pair of small soldering irons
joined at the hip.

A home-made jig can work pretty well for occasional use. The business
end is fashioned from a bit of heavy scrap wire, pounded flat and
notched to fit around the dimensions of the surface-mount component
that's the target. The other end gets jammed into your soldering iron
in place of the regular tip (although not all irons have heaters that
facilitate this). Or, use one of the iron's tips and file out an
appropriate gap to fit around the capacitor so that both pads are
heated simultaneously. This will ruin the tip, of course, so better to
either make the sacrificial wire tip or get a cheap iron (with
removable tips) and sacrifice it instead of your regular one.

As I understand it, sufficiently severe uneven heating of an MLCC
(possibly exacerbated by the mechanical shock that originally struck
it from the board) can delaminate it, which might have turned the
capacitor into conductor and lead to the dramatic end.

Re: Latop surface component breaks off
On 2/1/2013 4:48 PM, looking wrote:
Quoted text here. Click to load it
<http://en.wikipedia.org/wiki/Ceramic_capacitor#Multi-layer_ceramic_capacitors_.28MLCC_chips.29
Quoted text here. Click to load it

You want to measure the cap BEFORE you solder it back in.
Measure the volts across the pads it fell off and put that many volts
on the cap for a while and see if it heats up.
Quoted text here. Click to load it

It will take half a millisecond for someone to give a hundred examples
where the following is not true...but...statistically...
removing any one of the caps on the motherboard will likely NOT cause it  
to fail completely/catastrophically.

Are you absolutely/positively sure you have the right replacement jack.
Not all have the same pin connections, even if they fit the holes.
I'd check for shorts under the jack and in the vicinity where you  
soldered. The fact that the AC supply function didn't work is a clue
that something is wrong there.


Quoted text here. Click to load it
I have no idea your electronics experience level or the equipment
you have available.
There's a common power supply failure mode.
The internal resistance of electrolytic caps starts to increase
as you stress/age them.
If you start with 20V and switch it down to 3.3V for the processor,
the series resistance starts letting those voltage spikes through.
Eventually, you have a node that still reads 3.3V on your VOM, but
if you put a scope on it, you see 20V spikes with an average voltage
of 3.3V.  The caps on the 3.3V node don't like the spikes.
Nor does the processor that it is driving.  It may still work, but
have enough internal damage to overheat itself.

This can happen in the external AC supply and/or any of the switchers
internal to the laptop.

I've seen open power supply caps take out all the IC's on a monitor
board.
This is not typically a problem for small caps like you describe.

You can look with a scope if you can put all the heat sinks back on
with it disassembled and still get at the part in question.

Are we having fun yet?



Re: Latop surface component breaks off
There is a good possibility that you can just leave it out. There are lots  
of those caps all over the place and since this one is near the power jack  
it most likely only reduces EMI slightly.  

Chances are you overheated it reinstalling it. The first thing I would do i
s to see if it will fire up without it because there is a good chance somet
ing else is fried now.  

Hopefully that will just be a fusible link of some type.  

Computer equipment generates EMI all over the place. The PS is switched mod
e so it generates. There will be regulators on the mobo which are also swit
ched mode. Those caps generally smooth out the HF ripple not sufficiently f
iltered by the crapola SMD electrolytic nearby. This is not necessary for t
he operation of the circuit usually in a case like this. When you see one n
ear a big damn chip, that is a different story.  

But this is almost assuredly in the primary/power/charging circuit.  

If the thing runs without it, consider just leaving it that way. I'd say th
e odds of it still meeting FCC and CFR requirements are about 90 %

Re: Latop surface component breaks off
On Fri, 1 Feb 2013 19:03:55 -0800 (PST), snipped-for-privacy@gmail.com wrote:

Quoted text here. Click to load it
those caps all over the place and since this one is near the power jack it most
likely only reduces EMI slightly.  
Quoted text here. Click to load it
see if it will fire up without it because there is a good chance someting else
is fried now.  
Quoted text here. Click to load it
it generates. There will be regulators on the mobo which are also switched mode.
Those caps generally smooth out the HF ripple not sufficiently filtered by the
crapola SMD electrolytic nearby. This is not necessary for the operation of the
circuit usually in a case like this. When you see one near a big damn chip, that
is a different story.  
Quoted text here. Click to load it
odds of it still meeting FCC and CFR requirements are about 90 %

Very likely. Also, Muntzing.   ;-)
<http://en.wikipedia.org/wiki/Muntzing

Re: Latop surface component breaks off
put finger to keyboard and composed:

Quoted text here. Click to load it

odds of it still meeting FCC and CFR requirements are about 90 %

Quoted text here. Click to load it

He sounds more like an accountant than an engineer.

- Franc Zabkar
--  
Please remove one 'i' from my address when replying by email.

Re: Latop surface component breaks off

Franc Zabkar wrote:
Quoted text here. Click to load it
odds of it still meeting FCC and CFR requirements are about 90 %
Quoted text here. Click to load it


   No, he was a cheapskate.  He started the race to the bottom of the
barrel in quality consumer electronics.  Muntz TVs were a real bitch to
service.  By the time the crap hit a shop, it had multiple, interactive
problems, and the owners were as cheap as Muntz so they wanted them
repaired for $2 or less.  Very few shops would touch them, away from his
retail stores on the US West coast.

Re: Latop surface component breaks off
Hmmmm, the more things change.........

Re: Latop surface component breaks off

snipped-for-privacy@gmail.com wrote:
Quoted text here. Click to load it


  ...the more they end up in China...

Site Timeline