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Old 05-08-2012, 11:55 AM   #1
Scholzpdx
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Exclamation Bad capacitor on unused motherboard?

I have an ECS G31-T, socket 775 that came with my Q8200 a few years back. The motherboard has never been taken out of its box until now. It's been shielded and in a temperature controlled environment for years (ranging from 63F to 79F max). Upon unboxing it and doing a spot check, I found this!



This kind of bummed me out. A completely unused motherboard (out of warranty for sure) appears to have what I think is a leaking capacitor?

My main questions are, what is it really, and should I proceed building this computer?

Thanks in advance.
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Old 05-08-2012, 12:17 PM   #2
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Replace the cap before powering it up. Or at least cut it out of there. If you have an ohmmeter you can check if any other big caps are in parallel with it. If so then there is a good chance it will work well enough with that cap gone.

It looks like a 680uF 4V. lol I have handfuls of them laying around collecting dust. I'm sure you could find one somewhere for next to nothing. Do you have a soldering iron?

It is funny that the capacitor right next to it is of much higher quality...
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Old 05-08-2012, 12:32 PM   #3
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I do not presently have a soldering iron, however I don't think the cheapies are that pricey and it might be worth picking one up at radio shack. I am an electronics technician in the Navy and I get most circuit theory, but what other caps do I take a resistance check on, and how resistance should I be expecting.

That's for the help!

Edit: I also need a soldering for noobs video or guide, since my year long schooling provided zero hands on training. If you know of any good ones, don't be afraid to share it!
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Old 05-08-2012, 12:33 PM   #4
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This reminds of a news item a few years a ago about fake electrolytic capacitors that were made with a stolen but useless formula for the electrolyte.

Believe it or not, there even seems to be quite an extensive wikipedia page dedicated to the matter.

http://en.wikipedia.org/wiki/Capacitor_plague










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Old 05-08-2012, 01:56 PM   #5
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Caps can die even not in use. This is common when electrolytics are overfilled. Those K vent Polymers are actually fake caps. They should be solid, not liquid.
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Old 05-10-2012, 04:25 AM   #6
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The board has 6 layers of copper and requires an iron rated for at least 40-50W to thoroughly melt the solder. Melt 60/40 tin/lead solder (or 63/37) into each joint to lower the melting point of the lead-free solder already there, and do not pull out a lead unless the solder flows like water or you'll also pull out copper. Solder can be removed with either copper wick or a suction device. The choice of which to use is personal, but first practice on an unneeded circuit board.

Resistance and even capacitance measurements are rather useless since many capacitors are in parallel, but any capacitor with visible damage needs to be removed or replaced. Your photo indicates the ruptured one is a Sacon capacitor, 680uF, 4V, intended to resemble a polymer capacitor, and very likely you'll soon have to replace all the others identical to it. You should be able to use any polymer capacitor rated for at least the same voltage and capacitance, but a high quality Japanese brand conventional very low ESR capacitor, like Nichicon model HN, should also work. Watch polarity markings because some boards are labelled the opposite way of others. Notice your board uses the darker half of each circle to indicate positive polarity.

There are Youtube videos about desoldering, and guides and advice can be found at http://www.badcaps.net.
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Old 05-12-2012, 02:33 PM   #7
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Indeed some caps will vent just sitting unused whether they are soldered onto a board or just sitting in a bag. Their electrolyte isn't stable so after a while it breaks down and gas is formed.

Do not use any of the caps Radio Shack stocks, none of them have sufficiently low ESR for this circuit placement.

As bryanl suggested, pick something from a major Japanese cap manufacturer rated 105C temperature and very low ESR - if not solid/polymer as they can be rather expensive. Also consider putting the same caps in those unused positions on the board.

I don't feel they were trying to trick anyone by making them look like solid caps, the black stripe and punched out top stamp for venting purposes made it seem clear to me that they are electrolytic.

Determine if there are any other caps in parallel with the failed one. If there aren't, don't power on the board till a replacement is installed. If there are, you might remove the cap and try to power on the system just long enough to confirm it will post and is viable for a repair, worth the time and money to do so - but it's still possible it would be too unstable to post without a cap swapped in there since they already cheaped out and didn't populate the other two capacitor positions left empty. Do replace all those caps of same type in the VRM subsection and elsewhere they are used for switching power supply subcircuits, not just the one that already failed.

Another consideration is the CPU you intend to use. If it's a 95W model, the board may only be rated up to 95W if that and it might be quite a strain on it if the system will be under significant load much, let alone overclocked. On cheapie low power capability boards I try to stay quite a bit under their max rating and would look around the net to see what it would cost to go with a better board.
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