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.
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.
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.
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.
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?
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.
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.
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?
