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Capacitor problems- are they defective? Can I replace it with a similar capacitor or does it have to be the same?

Posted on 2011-10-07
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Hi, I have been having problems with a PC and all effects the system is experiencing hints the problem is in the capacitors. So I took the motherboard out and checked them visually and found many of them have a slight bulge to the top (instead of a slight depression). So below is a photo I took of them. I marked four of the capacitors with red x’s and three with green check marks, from what I see I would say the three with the check marks are good and the four with the red x are bad, would anyone agree? (I never heard of a bad capacitor prior to my research on this particular system I am trying to fix). So in other words I am just not sure if they are bulging enough to say they appear to be defective so I would like another opinion.


My next question is about replacement capacitors. For example the capacitor with the red x has the following written on it: 6.3V, 1800 uf, 105 C (temp), ATWB, 802A, and has a logo which reads TK.  The size is 8mm x 25mm. I found similar ones on ebay- the only difference is the manufacturer and the hight of the capacitors (the diameter is the same but the ones on ebay are slightly shorter, they are only 19mm tall). So would the ones I found on ebay be a good canadate? Or do I have to find the EXACT same brand? Here is the ebay listing I found:

http://www.ebay.com/itm/Rubycon-Electrolytic-Capacitor-1800uF-6-3V-105-C-10-pc-/280494288593?pt=LH_DefaultDomain_0&hash=item414ec32ed1



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Question by:hydrive1902
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John Hurst earned 400 total points
ID: 36934329
If the replacements have the same capacitor and the same or better voltage and temperature ratings, then they should work.

That does beg this question:  New capacitors will likely be smaller. Therefore the board is older. Is it worth it?

.... Thinkpads_User
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by:Dave Baldwin
Dave Baldwin earned 400 total points
ID: 36934408
If you're good at soldering, the caps look good to me.  If you're not experienced in soldering on multilayer boards, you could have problems.  I have fixed several motherboards and an HP monitor by replacing caps that were bulging.  But I have been repairing equipment for a long time now.
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by:hydrive1902
ID: 36934446
Originally I was thinking the same thing (just replace the whole board). Turns out the board (mcp61pm-hm) goes for 85 bucks in USED condition. Upon my research I found out that bad capacitors are a known issue with that model number of the motherboard so instead of me buying a used one (which probably will have the same issue sooner or later) I figured why not address the real problem...the capacitors.

So if I can replace all of the bad capacitors for 15 bucks or so then its definitly worth it because other then that issue the motherboard works perfect. Not to mention I have a 3 in 1 rework station so physically removing the bad capacitors and reinstalling the new ones would be more then simple, probably 20-30 seconds for each one (there is maybe 15 bad ones) so would take less then 5 minutes to install them all. Well worth it in my opinion.
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by:hydrive1902
ID: 36934456
Dave- what do you mean when you say they look good to you. Do you mean they look like good candidates for replacment or do you mean they look good (as in they dont need to be replaced at all)? I am pretty sure you mean they look like good candidates for replacment but just would like to clarify.
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by:John Hurst
ID: 36934468
So then if you are good at replacing them and you have the equipment, then go for it. I can see the bulge on at least one of the marked capacitors.  I hobby in electronics and I can understand your overall position here.

.... Thinkpads_User
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by:Dave Baldwin
ID: 36934474
I meant that the replacement caps look good to me.  I would replace the bad caps on the motherboard.
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by:garycase
garycase earned 400 total points
ID: 36934539
The replacement caps are fine ==>  the physical dimensions don't matter as long as they fit in the allocated space (and they're the same diameter, so that's not an issue).     The important factors are the correct capacitance and acceptable voltage and temperature ratings.    The ones on e-bay easily meet those requirements.

You've probably already seen this, but here's a good tutorial on doing your own re-capping:
http://www.badcaps.net/pages.php?vid=32

By the way, I wouldn't differentiate between "good" and "bad" caps on the board ==> if you're going to recap it, do them ALL.    It's only a few more minutes and a few more bucks ... but the board will be effectively new when you're done.

By the way, the badcaps folks (www.badcaps.net) sell complete kits of capacitors for most motherboards.    Not sure if your board has many other than the 1800uF units you're already planning to replace ... but it might be worth a look.     A full re-capping of the board will put it in essentially new (or even better-than-new, since the caps you'll use are likely higher quality than the originals) condition.
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by:nobus
nobus earned 400 total points
ID: 36935020
>>  from what I see I would say the three with the check marks are good and the four with the red x are bad, would anyone agree?  <<   NO - as gary said above do them ALL, you can see by the bulging the worst ones; but if they are not bulging does not mean they are still ok; and even if they are, they are going to be bad in the next couple of months

as for the brand -i would PREFER another one, since the same can lead to the same problem
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by:gismo51
gismo51 earned 400 total points
ID: 36936151
Electrolytic capacitors have two parameters that aren't usually marked on the parts and only available from the manufacturer's datasheet: ESR (effective series resistance) and max AC current.  For many applications they aren't terribly important and any cap with the same or higher voltage rating and same (or in some cases same or higher) capacitance.  But in a switching power supply (which is likely the application here) they can be critical. The existing caps on your MB were made by a Taiwanese company called Toshin Kogyo but I couldn't find their datasheet.  The Rybycons you found for replacement appear to be well suited to this application with low ESR and high ripple current ratings plus Rubycon has a good reputation for reliability so I'd go ahead and replace them all as others have suggested.

Before removing an caps, make a diagram on paper showing the polarity marks so you can be certain to install the new caps the right way.  Most are marked with a string of '-' characters down one side.  It wouldn't hurt to take a few more pictures (preferably in better focus) from different angles but sometimes the polarity markings are hidden by adjacent components and if that's the case you may need to note the orientation of one cap after removing it's neighbor.

These components are some of the easiest to remove from a circuit board as long as the opposite side of the board is accessible (likely).  You should use a temperature controlled soldering iron with a decent tip and either a "solder sucker" (pneumatic device that pulls molten solder from a joint) or solder wick (braided copper mesh with resin), either of which are available from Radio Shack.  First you should remove as much solder from each leg of the caps using the sucker and or wick.  With the sucker you must heat the joint for several seconds (until the solder has been liquid for 5-10 seconds) then while still heating the joint, place and trigger the sucker over the hole.  With wick, you just place a clear piece of it on the joint and heat it and the joint with the iron.  When the solder melts it will flow into the wick.

Once that's done you should heat one lead and attempt to tilt that cap so that it pulls the lead through the board a bit.  Then do the same thing on the other lead tilting the cap the other way.  Don't use a lot of force on the cap and you will likely have to repeat the process two or more times because the lead not heated will limit how far you can tip the cap.  If you use too much force it's easy to rip the traces from the board as they are just glued on.  Patience is a virtue here.  Also note that some of the leads may be soldered into a very large trace (which may be on an internal layer, and that means you need a lot more heat.  If a joint appears to take a long time to melt, this is likely why.   A temp controlled iron will help here.

After the caps are out you'll probably need to remove more solder from the holes before you can get the leads on the new ones to go in.  The sucker works best for this but wick and or blowing through the hole when it's hot or even pushing/pulling a spare piece of copper wire through the hole will work.  Just don't get carried away with force so you don't rip traces.

When you install the new caps (I'd do this one at a time) double check the orientation and then pass the uncut leads through the holes.  Try to rest the board on the cap (some foam rubber under the caps may help) so that it sits tight against the board.  Solder only one lead of the cap (they're much easier to remove or reposition with only one soldered) and recheck the fit and orientation, then solder the other lead.  Use just enough solder to leave a tiny "mountain" around the lead.  Apply heat to the wire and board (iron tip touches both) for a few seconds then while still heating apply solder.  If the joint is hot enough the solder will melt instantly and "flow" into the joint with obvious surface tension making it "stick to the lead and board.  Remove heat and let it cool for a few seconds without any movement between the cap and board (movement will make the joint fragile).  The surface appearance will change when the solder solidifies, that's when movement is OK.

Once the leads of a cap are soldered in, clip them off as close to the board as possible with a small pair of cutters.  Ideally the clipped wires won't protrude any further than other's you haven't worked on, but the main thing is to make sure they can't touch something conductive when the board is installed.
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by:Dave Baldwin
ID: 36936391
I would gently work the caps out before removing any solder but otherwise I agree.
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Author Closing Comment

by:hydrive1902
ID: 36940846
DaveBaldwin- I understand now what you meant about saying they look good I thought you said the ones I thought were defective look good- which was not the case. Thanks for the clarification.

Nobus- Great point haha!

gismo51- thanks also for the extensive info. you provided.

Garycase- thanks for that other good website I had not seen that one prior to your posting it here.

And of corse thanks thinkpads_user- the first responder!
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by:John Hurst
ID: 36941886
Thank you. I was pleased to help. ... Thinkpads_User
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