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Capacitors and the Computer PSU Mon, Mar-05-2007
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Introduction:(22169 Reads)
Capacitor. The very word conjures up profound indifference amongst my family members every time I use it in conversation, which is surprisingly often. But, as many of you are aware, they are of profound importance to the operation of a Switch-Mode Power Supply, or SMPS for short. Today we will be taking a close look at how different quality capacitors can affect a computer power supply's output.


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Capacitor. The very word conjures up profound indifference amongst my family members every time I use it in conversation, which is surprisingly often. But, as many of you are aware, they are of profound importance to the operation of a Switch-Mode Power Supply, or SMPS for short. Today we will be taking a close look at how different quality capacitors can affect a computer power supply's output.

An SMPS is inherently a very noisy device. Not noisy as in listening to my local fire siren from ten feet away mind you (I'll never do that again), but noisy as in alternating current showing up on the DC outputs where we don't want it. It is impossible to eliminate all such noise due to the very nature of SMPS design, but through good filtering we can reduce it to an acceptable level so our motherboards and hard drives don't cook while we're fragging some poor shmoe in the latest hot shooter or playing Oblivion for the forty billionth time through.

I will be experimenting on two patients in this article. The first victim, er... PSU is an Antec Neopower 480W constructed deep in the factories of Channel Well Technology. The second unit is a first generation Fortron-Source FSP600-80GLC Epsilon I originally purchased shortly after its Canadian debut and then promptly traded for a Silverstone ST56ZF. Both of these units, in their own way, have been the cause of much discussion and speculation among the PSU sections of the more well known computer hardware forums due to some interesting test results and high profile failures - more on that as the article unwinds.

My experiment on these units will take the form of what initially seems a very simple procedure: take out the old capacitors and put in better ones. But, there are a few things to keep in mind when doing so. First, the quality of the replacements is important - we want high grade, low ESR (Equivalent Series Resistance) capacitors with nice long lifespans. Not just any brand will do. And we want them to be rated at 105 degrees Centigrade, for you see 'tis the nature of a computer power supply to run at warm and sometimes very warm temperatures.

For this article, I chose KZE and KY model capacitors from United Chemi-Con, a well respected company that has been in the cap business for decades. Some other excellent capacitor manufacturers are Matsushita (Panasonic), Rubycon, Nichicon, Samxon, and Sanyo. These can be obtained in several places online around the world; my own source is usually www.digikey.com where they have an excellent selection.

Before we go any farther, in order to replace capacitors you must be handy with a soldering iron. While soldering and desoldering capacitors is not hard, it does require some basic familiarity with soldering. Yours truly has been doing it regularly since age fourteen, so what is second nature to me may prove difficult for you. If you are uncertain you can do this successfully, please don't try until you've practiced on something you can afford to destroy; like the next door neighbour's constantly cranked stereo or something. Just don't get caught, and make sure you have an alibi.

And now, some tools of the trade:

Most of these are pretty easy to identify. We have a spool of solder, small needle-nose pliers, a screwdriver, a massive Soldapullt solder sucker, a 40 watt Archer soldering iron, and a terminal block with a needle in it. You might be asking, "A what with a what in it?"

This is my preferred desoldering tool for computer mainboards and other stubborn multi-layer PCBs. Because this is a stainless steel sewing needle, solder doesn't stick to it. This makes it handy for use around surface mount devices where that big blue solder sucker is perfectly capable of wiping out whole rows of tiny components with a single slip. It also offers the advantage of not dropping little solder boogers all over what your working on if you've forgotten to clean it.

For this article, I didn't use the needle in the terminal block due to being very experienced with the big solder sucker, and also for the reason that neither PSU had a multi-layer PCB to complicate things. I also didn't use that 40 watt iron above, opting instead for a more powerful 60 watt borrowed from a friend. I'll explain why later on.

A quick word about the soldering environment: while a computer PSU usually will not contain many static sensitive components, if any at all, it is always a good idea to solder using a wrist strap, grounded soldering iron, anti-static mat, or a combination of the three. I like to live dangerously, so I went with none of the above. Do as I say, not as I do!

Here we have a picture of the enemy, three failed capacitors that can cause all sorts of fun things in the computer while you're trying to get your game on, from spontaneous restarts to strange hissing noises to failing to power on to giving you a light show to rival the best Independance/Canada Day fireworks. The middle capacitor is actually from an Epox mainboard, but I tossed it in there anyway so Fuhjyyu didn't think I was exclusively picking on them.

Now, without any further ado, let's move on to our first victim.

 




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