Need bad capacitor help - Fiberglass RV


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Old 03-09-2014, 07:53 PM   #1
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Need bad capacitor help

This question is off topic -- it is aimed specifically at any member who is electronics savvy --i.e. has more knowledge than me on the subject of capacitors.
I took this picture of a capacitor I suspect is gone bad and needs replacing. Will someone confirm that for me? It is the only one on the motherboard with that nut colored residue on top. If it needs replacing can I snip it off and re-solder on a replacement? Thinking I am up to this level of brain surgery but don't know what tricks to employ to get it done without shedding blood.
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Old 03-09-2014, 08:30 PM   #2
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It certainly doesn't look healthy, but what caused it to do that may do the same thing to a new one. I'm guessing it's serving as a filter capacitor of some sort by it's ratings

That's a cheap enough part, just be sure you watch for polarity markings and go for it.
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Old 03-09-2014, 08:48 PM   #3
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Thanks for the quick reply. Quick history: this 7 yr old tv was in storage the last couple years. When I turned it on a couple weeks ago the picture was superb but sound absent, except for a low, dull, rapid clicking that after nearly an hour evolved into normal sound. Then 2 days ago, after 2-4 hours, no sound at all except the same clicking. Went online seeking answers and that has got my focus to this point.
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Old 03-09-2014, 08:52 PM   #4
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While I do not see any bulge in the top of the capacitor, this looks to be an internal corrosion issue. If the electrolyte had been mixed incorrectly as so many were, it would likely have bulges from over pressure, and the residue would then be a much darker color. The light color typically happens when it eats through the edges of the aluminum case at the stress points. (Corners.)

Mark the polarity on the board (just in-case it isn't silk screened on the board) with a marker first. Capacitors sound like firecrackers when the polarity is reversed!
To remove the capacitor you should pull the motherboard out and flip it over. Heat each pin separately. Push on the side of the capacitor toward the top. Push the same side as the pin you are heating, causing leverage to pull the pin slightly through the motherboard. Then do the other side. Allow the board to cool for a few seconds between each so you limit the chance of lifting a pad.

You will feel the capacitor tick and tilt slightly to the side. Do this back and forth until the capacitor works its way free on one pin. From there heat the remaining pin and pull it straight out. The hole should clean up and be ready for a new capacitor just by running your iron over it. If not, heat it then use a solder sucker or blow on it with a straw to get excess solder off. I would recommend the sucker or an eye dropper though, since this is a motherboard. You don't want to spray solder all over it!



Funny that this ends up being my first post here, but I am an electronics tech. I have built many computers, and replaced many capacitors!

Hope this helps!
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Old 03-09-2014, 08:53 PM   #5
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I'm not electronics savvy enough to help. I do know my limitations though. Soldering on a MOBO can be pretty tricky, so you might want to find a pro. Chances are you can replace the entire MOBO for less than the cost of getting someone to solder it for you.
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Old 03-09-2014, 09:15 PM   #6
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Thank you so much, Kenji! You have given me exactly what I was hoping to learn; solid, practical, unvarnished instruction. Truly appreciate your guidance, and welcome to the forum. I've been a member a long time - one thing I know for sure is the members here possess a massive amount of expertise, experience and knowledge, on a wide variety of topics. I took a shot with my inquiry exactly for that reason.

Here,fiberglass trailers is just the tip of it all. Welcome to the forum!
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Old 03-09-2014, 09:20 PM   #7
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Thank you, glad I could help!
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Old 03-09-2014, 11:03 PM   #8
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Quote:
Originally Posted by Roy in TO View Post
I'm not electronics savvy enough to help. .
But he did ask for "bad" capacitor help.......
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Old 03-10-2014, 01:02 AM   #9
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THat capacitor does look bad, but it may have failed because another part of the circuit fed too much voltage into it. If I were troubleshooting it, I'd look for a bad transistor somewhere along the same trace.

On the other hand, capacitors are cheap, and, if you screw up while soldering or there is another bad component, all you've lost is a dollar or two and an already-defective circuit board.

That's an electrolytic capacitor. It has a stripe going down one side to indicate polarity, so, if you unsolder it, make sure the replacement has the stripe going down the same side.

This capacitor is rated for 16 volts. You can replace it with and 1000F electrolytic capacitor rated 16v or higher. Because this one looks like it was over-volted, I'd probably look for a 25v capacitor to replace it with.

You can buy these on eBay for a dollar, including shipping from Asia, a bit more if you order from a North American shipper. You'll also want some solder, a soldering iron, and some de-soldering wick, all available from Radio Shack.
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Old 03-10-2014, 07:28 AM   #10
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A bad electrolytic capacitor is a common failure. Many of the television sets you see discarded have failed electrolytics. If you have a multimeter you can perform a simple test. With the capacitor removed, short the leads with a screw driver. Set your meter to a high resistance scale, say 20k ohms or 200k ohms. Observing polarity (usually the negative lead on the capacitor is labeled) attach your meter. You should see the readings increase with each sample the meter takes until you reach an open circuit. The higher the resistance scale, the longer it will take. This will tell you if the capacitor will hold a charge. If the meter sits at zero, the capacitor is shorted. If reads open with no counting the capacitor is open. Either way replace it.

When I replace components I prefer to drill the holes out with a #60 or #70 drill bit as continually heating tends to cause the traces to lift off the board.

Replacement capacitors are easy to find for free in discarded equipment of which we seem to have lots these days.
Good luck, Raz
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Old 03-10-2014, 09:02 AM   #11
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Originally Posted by P. Raz View Post
A bad electrolytic capacitor is a common failure. Many of the television sets you see discarded have failed electrolytics. If you have a multimeter you can perform a simple test. With the capacitor removed, short the leads with a screw driver. Set your meter to a high resistance scale, say 20k ohms or 200k ohms. Observing polarity (usually the negative lead on the capacitor is labeled) attach your meter. You should see the readings increase with each sample the meter takes until you reach an open circuit. The higher the resistance scale, the longer it will take. This will tell you if the capacitor will hold a charge. If the meter sits at zero, the capacitor is shorted. If reads open with no counting the capacitor is open. Either way replace it.

When I replace components I prefer to drill the holes out with a #60 or #70 drill bit as continually heating tends to cause the traces to lift off the board.

Replacement capacitors are easy to find for free in discarded equipment of which we seem to have lots these days.
Good luck, Raz

Be careful drilling out holes in printed circuit boards. Most are plated inside the hole and provide connection from one side of the board to the other. If the 4 layers or more connection to an internal layer is provided by the hole plating. Ground planes are often one the inner layers, that capacitor one lead most likely connects to ground plane. Even if it's a two layer board you can't get to the top lay to solder the lead. Solder wick is generally used to clear the mounting holes.
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Old 03-10-2014, 09:28 AM   #12
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Originally Posted by Byron Kinnaman View Post
Be careful drilling out holes in printed circuit boards. Most are plated inside the hole and provide connection from one side of the board to the other. If the 4 layers or more connection to an internal layer is provided by the hole plating. Ground planes are often one the inner layers, that capacitor one lead most likely connects to ground plane. Even if it's a two layer board you can't get to the top lay to solder the lead. Solder wick is generally used to clear the mounting holes.
Hey Byron, welcome back. As far as plated holes, that's why I use the small drill bits. Raz
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Old 03-10-2014, 04:19 PM   #13
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-How do you know that capacitor is...bad? Not by the look, though...Either you test it with capacitor tester or use the old way to determine whether it is bad or not-remember capacitor charges and discharges electrical energy....
-To take it out, apply the tip of soldering tool on one side of circuit board, wait until the solder hot enough and melt then use your hand, pull the capacitor out from other side of circuit board. Do the same thing when install the new capacitor in-no need of drilling, cutting...ect...-
-1000microfara rating is usually used for filtering. 16Volt rating is used for 12volt circuitry, usually. Make sure to install new capacitor with the proper rating and...CORRECT POLARITY. Just my thought...
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Old 03-10-2014, 04:22 PM   #14
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One more thing, there are tons of this kind of electrolytic capacitors in any thrown-away old tivi, vcr, stereos-in paticularly from AC/DC adaptors- if you want to have them....FREE.
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