Capacitor question

[RewopEldnac]

I have some capacitors blew on my motheboard (Abit KT7A-Raid). They are rated 2200 ìF at 6.3 V. I am going to try to replace them myself. I checked my local electronic store (MarVac), they only have the one that is rated 10 V. And the guy told me that it is ok, and the important thing is the value of the Farad. Is that true? /ubbthreads/images/graemlins/help.gif

 

[php_44]

There's a few things to look for. The capacitance (usually in uF - microfarads), the voltage, and the ESR (a measure of the resistance of the capacitor). The ESR is important in switching power supplies and some parts of a computer mother board (like near the CPU). I'd probably go for a low ESR part.

One thing more: If the caps blew - there is probably a reason they did. If your power supply went wacko and exceeded the caps' voltage rating then your motherboard probably has much more extensive damage. (this is probably what happened if they actually swelled, vented, or popped open). If it was heat - you'd better look into cooling issues. (This might look like dried leaked fluid around the caps). If they were just lousy caps you might be OK to replace them and get more life out of your board.

 

[JSWrightOC]

I have had identical problems on various motherboards. The boards are fine, and most of the time (unless all caps on the Vcore regulator are blown) the motherboard keeps running happily along. The problem is with the caps. There must have been a bad run of them from some manufacturer, or they are just plain cheap. I have replaced all the Vcore caps on my motherboard (Abit KA-7, very very similar) and have never had a problem since. Actually, even with half the caps blown it continued to run but I replaced them all anyway. /ubbthreads/images/graemlins/tongue.gif

As for the WV, capacity and ESR ratings, you can install a cap with a higher WV rating than the unit you are replacing, though it will likely be physically bigger than what was originally installed. For power supply filter caps, you can often fudge the capacity one way or another, but it is better to go up than down. ESR ratings, though not widely published, are critical for proper operation of the power supply and capacitor longevity. I have had excellent success with Panasonic's FC series caps (available from DigiKey).

Those 6 and 8 layer PCBs are a pain to solder to...good luck!!

 

[Kram]

For what it's worth, I read in the trade press about a year ago that widespread problems (mostly on computer motherboards, incidentally) with capacitors from Asia had appeared. Apparently, those components were substandard/defective and they were failing in the manner you described. At this point, I'd hope that most of the bad ones have worked their way through the inventories. You're probably fine with just replacing the failed ones.

 

[RewopEldnac]

[ QUOTE ]
JSWrightOC said:
As for the WV, capacity and ESR ratings, you can install a cap with a higher WV rating than the unit you are replacing, though it will likely be physically bigger than what was originally installed. For power supply filter caps, you can often fudge the capacity one way or another, but it is better to go up than down. ESR ratings, though not widely published, are critical for proper operation of the power supply and capacitor longevity. I have had excellent success with Panasonic's FC series caps (available from DigiKey).

[/ QUOTE ]


what is the ESR rating on that Panasonic's FC series caps?
And how do I find out about the ESR rating on the original caps?

 

[JSWrightOC]

The Panasonic FC series is optimized for low impedance. Data is available on their website in the form of an Acrobat PDF on page 2.

Their main capacitor page is located here.

 

[RewopEldnac]

Thanks for all the help

 

[MisterEd]

Some more information on motherboard caps -- there was a big scandal over the caps going into PC motherboards some months ago. Basically it went something like this: Someone stole the formula for the electrolyte from their employer and sold it to a rival capacitor manufacturer. However, they missed a few steps or left out some key details or something, and the result was that the caps would appear to work but wouldn't last very long before they blew up or the electrolyte leaked out etc. These caps found their way into many motherboards, since they were available quite cheaply.

The upshot is that there could be nothing at all wrong with your power supply, onboard voltage regulators etc. It could have just been bad caps.

Here's a good article on the topic.

 

[RewopEldnac]

MisterEd, that is exactly the article I read months ago, but I thought that my MoBo is an exeption, but I guess it is not.

JSWrightOC, thanks you, I am going to go ahead order from digikey.

 

[INRETECH]

Another problem is cleaning the boards with a CFC based solvent, it will migrate into the cap, react with the electrolyte and cause the cap to have properties of a bettery, when current is applied to the cap, they will overheat and explode; even before the fuse blows

 

[RewopEldnac]

[ QUOTE ]
INRETECH said:
Another problem is cleaning the boards with a CFC based solvent, it will migrate into the cap, react with the electrolyte and cause the cap to have properties of a bettery, when current is applied to the cap, they will overheat and explode; even before the fuse blows


[/ QUOTE ]

Oh yeah.. now you remind about the yellowish liquid all over the mobo that came out from the blown caps. What can I use to clean it safely?

 

[The Yeti]

abit had a bad batch of capacitors. Their cap supplier used a cheaper vendor who had stolen the method of how to make the caps from their largest competitor, however there was a step missing. Due to that the caps fail after 1-3 years. I would reccommend calling abit. I belive that they had a recall of several lines of their motherboard due to blown caps.

 

[JSWrightOC]

Speaking of overheat and explode...

I happened to be playing an FPS video game when one of the caps died on me. It sounded like a muffled pop followed by a hissing sound. I jumped, cause I didn't know what it was (being in the mindset of playing the game!!) and when I realized it was something in the computer I quickly shut it down. Aside from the sound, I wouldn't have known it had happened. The computer kept running like nothing had happened.

 

[JSWrightOC]

Sorry, my first post got delayed...

I have successfully cleaned the electrolyte with isopropanol (rubbing alcohol). I think any ionic cleaning agent will work fine, however.

RewopEldnac,

No problem, I ordered my caps from Digi-Key, installed them, and my computer has been running great for two years, no problems.

 

[snakebite]

change all the caps that say tayeh jackcon stone ect.
the panasonic caps are what i use.
take it from someone who has rebuilt 500+ abit bad cap boards.

 

[RewopEldnac]

OML 500+!!! /ubbthreads/images/graemlins/ooo.gif

I only ordered 10 Panasonic caps, 2200 mF, 6.3 V. I hope that is all I need.

JSWrightOC, that is the same sound I heard, twice. Scare me to death, and I shut down my computer as soon as I can.

Other than Abit using cheapy caps, before the 1st cap blew, I upgraded my CPU to XP 2000+ could that have trigered this problem?

 

[INRETECH]

There is very little chance of a operating system causing caps to blow, as mentioned in the thread, I agree its a run or "batch" of bad caps

 

[RewopEldnac]

Oh sorry, what I mean by "XP 2000+" is an AMD XP 2000+ cpu running at 1667 GHz, and not Microsoft Windows XP.

 

[koala]

Yes go for panasonic, they are great cap and also good rechargeable battery manufacturer. I've use their supercap in my embedded systems for a long time, they have high farad ratings.

You can identify *pop* potential by simply looking at the caps, they will buldge on the top. And in case you have never seen a poping cap before, a 240v 2200uF cap can blow so hard that rings your ears if you connect them opposite way. BAD cap manufacturer labling their caps the other way round /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif. I am glad it is enclosed in a powersupply case, else, imagine flying aluminium chips, electrolit juice and etc. So buy only quality components. A few penny is not worth the risk to a robust system.

Vince.

 

[RewopEldnac]

Just an update.

Pathetically, it took me about 3 hours just to replace 9 capacitors. But I can't describe the feeling, when I put everything back together and it works. /ubbthreads/images/graemlins/grin.gif

Once again, thanks to all of you. You guys are /ubbthreads/images/graemlins/thumbsup.gif /ubbthreads/images/graemlins/buttrock.gif