By Noah Adams (aka DooD).
What are bad capacitors?
Bad capacitors or "bad caps" as they are known, have come about due to several different mistakes in the capacitor industry.
To start it all off, it was believed that an electrolyte formula was stolen from a primary manufacturer of capacitors, which was incomplete. When the thieves of the formula attempted to reconstruct the missing pieces of the formula they failed. While this is just one of the possibilities, it seems to be the most common explanation. What occurs is that while the caps using this formula seem to work fine for quite a while, the electrolyte is actually slowly breaking down into hydrogen gas, which is why bad caps often have their vents on the top pushed up and leaking.
There are also other factors that come into play with bad caps. Sometimes the cheaper manufacturers of electrolytic capacitors don’t do a very good job of seating the rubber plug in the bottom, which seals the cap around the legs. This can sometimes cause the electrolyte to dry out, without actually showing any outward symptoms.
Also, heat can play a large factor. Sometimes even known good brands of capacitors fail due to excessive heat. This is a large problem in the Dell GX270/GX280 machines, where the capacitors are largely packed in next to some very hot heat sinks. Also, simply using the wrong specification of cap can cause similar problems. For example; using a capacitor rated to handle a temperature of 85*C when you know it will be subject to temperatures much higher than that.
So why do I care about all this?
In general, you may not care... but chances are that if you have been working with computers much in the past 5 or 6 years, you have been affected by bad capacitors. They’ve been known to show up on motherboards, expansion cards, power supplies, as well as anything else that uses an electrolytic cap. There have even been reports of caps failing on automobile ECU’s, and mobile electronics devices (stereo head units, amplifiers, and so on).
A cap may actually take years to fail to the point where you notice it in daily operations. Other times, it can only take months; it all just depends on the circumstances. Common symptoms of bad caps on your motherboard or in your power supply are general instability, slowness, or loss of onboard features such as USB ports or serial and parallel ports. A common problem when power supplies have bad caps is that the machine will not always turn on first try. Sometimes you have to turn it off and on several times before it will start up. These are all things that can tell you that you have bad caps.
Positive Identification
The best way to confirm whether you have bad caps is simply to look at them. Although caps have been known to fail without outwardly signs (specifically Teapo brand capacitors), you can most often tell that a cap is bad just by looking at it. Here are some examples of bad capacitors:
In this first picture, we can see that there are two smaller caps that have pushed the rubber bung out instead of venting to the top. This means that the caps were not properly made at the factory.
Here we have four capacitors right next to some MOSFET heatsinks that have bulged due to heat. Note that it’s a slot-A Athlon board, so it’s quite old. The board was still operating normally when this picture was taken, but we chose to recap it to avoid future failure. See below:
Here are the caps that were removed from the above board. All but one is pushed up at the top vent. This is how they commonly show failure. You do also sometimes get crusty deposits around the vent, and we’ll see that a little later.
One of the old caps next to my choice for the replacement part.
The recapped board. I tried to mount the new caps so that they were not butted right up against the heat sinks again... hopefully this will increase their lifespan. Most people will recommend replacing all of the caps on a board, whether they’re visibly defective or not, but in this case, space and time was tight, so I went for the easier route and just did the 4 affected caps. This board will probably last much longer than the owner cares for it to?.
And finally, we have an Antec SL300S power supply with bad caps where marked. Keep in mind that even expensive power supplies may have bad caps! I’ve also had an Antec TruePower 550 fail, and I’m guessing it was due to bad caps. I could not tell for sure, though, because it was still under warranty and I didn’t want to open it up.
Recap the board yourself
If you’re handy with a soldering iron, you can recap the board yourself, with minimal cost or time spent. You can order caps from www.digikey.com or www.mouser.com. You should always try to match up your cap values, and if necessary go a little higher in values. Also keep in mind the diameter of the cap. You need to stay the same or a smaller part if the caps reside in a tight spot on the motherboard. Make sure that you purchase LOW-ESR caps! They are the only caps suitable for motherboards!
For soldering irons, I have to recommend 40 watts or one with higher heat capabilities. You will also need a pair of dikes, some needle nose pliers, and possibly a good sharp pin.
If you apply heat to the underside of the board, where the legs of the cap come through, you can rock the cap out one side at a time. It may take some switching back and forth between sides to get it all the way out. Make sure that you are only applying heat to the legs of the cap, and not to the board itself. Also, try not to dwell on one leg too long, or you can damage the vias (holes in the board that the legs go through), and ruin the board forever.
If, when you’re trying to remove the old cap, the leg comes off of the bottom of the cap and gets stuck in the hole, you can simply grab the remaining leg in the board and pull it out with your needle nose pliers (while heating the underside, of course). This problem commonly occurs on cheaper caps that are not well-built.
Now you need to decide if the holes that you left behind are suitable to just drop the cap right in or not. Some solder left in the holes is normal, but if you ended up with a large glob of it somewhere, you may need to clean it out by heating it and removing the solder with the pin that you have. Again, always be careful not to damage the holes!
To get the new cap into the hole, I usually cut the leads down quite a bit to make them stiffer and less prone to bending while I’m working with it. You don’t want to go too far though, because you do need some sticking through the other side of the board, and you can trim it later.
Line the legs of the cap up with the holes on the surface of the motherboard. Make sure to orient it in accordance with the marking on the board. The striped side of the cap should always go towards the shaded part of the board. These caps are polarized! While using a fine tip on your iron, flow the solder that’s left in the hole and gently push the cap through, using the same motion you did to remove it. Work it in just a little bit at a time so that you don’t overheat the board or bend the leads too much.
Once the cap is completely set in the holes, you can trim the leads back and flow some new solder onto the remaining leads to secure the cap in place. A gentle wiggle of the cap while watching the leads for movement will tell you if it’s made good contact or not.
After you do this to all the caps that need to be replaced, fire the board up and hope for the best. PLEASE NOTE- this is just my method of recapping. I can not be held responsible if you damage your motherboard while doing this. It DOES take practice, so start on some junk boards you don’t need. You can even practice on an old board that doesn’t need to be recapped. Just remove the caps and reinstall them, and see if it works. Practice on that old Pentium II board you have laying around, and if that goes well, then move on to the bigger fish!
I don’t want to do it myself, will anyone do it for me?
Well, that’s no way to go through life, but I guess in this situation it could be understandable. Maybe you’re just uncertain of your own skills and want to have a higher possibility of getting your board back up and running. Whatever your reason, there are people out there who offer to recap boards for a nominal fee. And look at that... I’m one of them!
Just send a Private Message to me here on the Dalantech forums, or shoot an email to dalrecap@gmail.com and we can discuss your specific board and what you’ll need done (plus the fees, which, I promise, are quite reasonable!)
I cannot guarantee that a recap will bring a dead board back to life!!! Recaps cannot be guaranteed 100%! I will inform you if I ran into any problems along the way, and if the board does not come back to life you will not be charged for any new caps, as they will not be left on the board unless you request it. You may be charged for time, however.
When I recap a board, I put it through a multitude of stress tests to ensure that it is operating normally before sending it back to you. It undergoes 24 hours of memory stress using Memtest86+, and then I load a spare hard drive with windows XP and run the distributed.net client for another 24 hours to ensure that it can properly supply power to a loaded CPU.
I only use the highest-quality low-ESR capacitors when doing the replacements, and I buy in bulk to keep the overall cost-per-cap down!
Due to the testing phase, it may be 3 days from the time I receive the board until I can get it shipped back on its way to you. Times may vary depending on my current workload, but it should never be more than 4 days. If a delay is expected, you will be notified immediately.
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