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Bad capacitors : How to spot them

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#1 +warwagon

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Posted 31 August 2012 - 16:23

Bad capacitors can happen on any motherboard, new or old. They can also explain issues that are other wise unexplainable.

1) Computer won't turn on
2) No display
3) Random bluescreens
4) Lockups

Just to name a few

When looking for bad capacitors on a motherboard, it helps to know what a healthy one looks like first.

A good capacitor usually looks indented, when viewing it from the top. In fact if you rub your finger over it you can feel the indentation


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A bad capacitor or one that is starting to bulge will start to swell at the top, no longer looking indented








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http://www.pcstats.c...m?articleID=195






Others swell to the point of blowing thus you can see electrolyte brown crud on the top of the capacitors.






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Others Leak









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http://www.pcstats.c...m?articleID=195






In any case once you start to see the following symptoms it's time to either replace the motherboard, replace the computer, or know that the issue is not going away




#2 sc302

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Posted 31 August 2012 - 16:31

those would be blown capacitors. replace mobo or replace computer. it happens, usually due to heat/overheating, not enough to cause a thermal shutdown but enough to be above operating temp of the capacitors. is it common? yes, across lots of models and manufacturers. It is so common, that once pc's start acting crazy with blue screens and shut downs that the first thing I do is pop the cover off and inspect the motherboard.

#3 vetneufuse

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Posted 31 August 2012 - 17:11

if you have a newer motherboard with solid-cap's you won't find these signs generally... solid capacitor don't "bloat" like the older caps did

#4 OP +warwagon

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Posted 31 August 2012 - 17:12

Bare with me on the formatting of this thread. For some reason it wants to space out.

#5 CentralDogma

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Posted 31 August 2012 - 17:15

If you’re good with soldering, you can even replace blown capacitors.

#6 f0rk_b0mb

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Posted 31 August 2012 - 17:29

If you’re good with soldering, you can even replace blown capacitors.


Yup, that's what I'd do, however, it is not as easy as it looks. I had 2 years of electronics and my joints are never perfect.

#7 Rudy

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Posted 31 August 2012 - 17:33

My Samsung tv had bloated capacitors. At the end the tv would take 5-10 minutes to turn on (once on it was fine). I opened the TV and replaced the capacitors and it works great now

#8 Hell-In-A-Handbasket

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Posted 31 August 2012 - 18:49

OT

can see electrolyte


plant food in a computer ?


*edit - every time i see Electrolyte(s) i think of Plant food

#9 sagum

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Posted 31 August 2012 - 19:04

Yup, that's what I'd do, however, it is not as easy as it looks. I had 2 years of electronics and my joints are never perfect.


Through hole soldering is one of the easiest tasks to perform, can can be done with the most basic of kit. I've saved loads of motherboards, and monitors by replacing ALL the caps at once. They usually come in at the local electronics store at around £10 for goodie bag full, certainly a lot cheaper then replacing a motherboard or PC... and certainly less wasteful then throwing out a otherwise perfectly good monitor screen and backlight.

I replace all caps if i find any that have died. usually if one is bloated or leaking, its a bad batch or the others are on their way out (or have already but just not showing visual signs yet). There is always an under line cause, mostly its cheap or dodgy batch of caps used when making the boards.

Posted Image

I had some spare caps so I replaced just that one - it didn't work. So I replaced the rest, and even though they all looked fine, it fixed the problem.

#10 Crisp

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Posted 31 August 2012 - 19:09

Cannot I hit them with a hammer / screw driver to dent them again? lulz.

/s

#11 Mordkanin

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Posted 31 August 2012 - 19:11

Bad caps don't always bulge at the top.

An electrolytic will almost always bulge at the bottom first. You can tell if it's not resting flat on the board. (Source: I'm an EE. Also, I just ran a 10V 10uF cap at -15V for over a minute. Zero effect on the top of the cap.)

Be wary, when replacing capacitors. These days, organic polymer caps are coming into higher usage. They're used for higher ripple current applications and have generally better performance than the standard aluminum electrolytics.

If you replace one with an aluminum electrolytic, it'll probably overheat and fail very quickly, or lead to unstable operation from poor transient response, as they have an ESR an order of magnitude higher.

#12 OP +warwagon

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Posted 31 August 2012 - 19:23

Bad caps don't always bulge at the top.

An electrolytic will almost always bulge at the bottom first. You can tell if it's not resting flat on the board. (Source: I'm an EE. Also, I just ran a 10V 10uF cap at -15V for over a minute. Zero effect on the top of the cap.)


Can you post a photo of that. I'm looking but can't find one.

#13 ahhell

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Posted 31 August 2012 - 19:24

My Samsung tv had bloated capacitors. At the end the tv would take 5-10 minutes to turn on (once on it was fine). I opened the TV and replaced the capacitors and it works great now

Samsung lost a class action suit against them because of this. My DLP crapped out and I'm sure that this is the problem (that or bad solder connections).

#14 The Laughing Man

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Posted 31 August 2012 - 19:28

I remember the counterfeit cap issues from back in the day they were a huge cause of blow/leaky caps.

#15 f0rk_b0mb

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Posted 31 August 2012 - 22:07

Through hole soldering is one of the easiest tasks to perform, can can be done with the most basic of kit. I've saved loads of motherboards, and monitors by replacing ALL the caps at once. They usually come in at the local electronics store at around £10 for goodie bag full, certainly a lot cheaper then replacing a motherboard or PC... and certainly less wasteful then throwing out a otherwise perfectly good monitor screen and backlight.

I replace all caps if i find any that have died. usually if one is bloated or leaking, its a bad batch or the others are on their way out (or have already but just not showing visual signs yet). There is always an under line cause, mostly its cheap or dodgy batch of caps used when making the boards.
I had some spare caps so I replaced just that one - it didn't work. So I replaced the rest, and even though they all looked fine, it fixed the problem.


Yes! Through hole soldering is the easiest. I really hate the ones where they rest ontop of the board. Like this. Just got done fixing this for a friend. Works! :)