Some of us have fond memories of Grandpa, hunched over his workbench with a bright lamp overhead. The smell of burnt electronics and solder fills the air as he fixes an old radio. Back then the electronic parts were large, clunky items that would tell you when something was wrong. They communicated in excessive heat, the occasional spark or sometimes the release of the magic smoke inside that made them work.
Fast forward to today, and take a look at a modern circuit board. It is hard to tell a working board from one that has failed. Microchips and surface-mount components have an extra layer of mystery hidden in their tiny little forms. Electronic components and devices fail. This is an electrical-engineering fact of life. With the tendency of devices to be made much smaller and at much less cost, it has become increasingly difficult to troubleshoot when failures occur. Grandpa’s magic touch doesn’t apply any more.
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Now, it is usually more economically feasible to replace rather than repair. There are good repair services available, but often the cost of the repair is too close to the cost of a new component to justify sending it in. When this is the case, it often makes more sense to buy the newest version, which may also have improvements over the older version.
However, if the repair is quick and easy enough to complete it is often worth the time. Here are some simple repairs that can be done quickly and may end up saving you, your company or your client some money.
Electrolytic capacitors—caps—are often the cause of failure of a board. They are generally there to filter noise or ripple out of dc voltages.
When they fail, it is normally due to loss of electrolyte through leakage or vaporization. This decreases the capacitance and can cause voltage issues on the board, leading to failure.
The signs that the capacitor is the problem are discoloration on the board below the cap where it has leaked or a bulging top of the cap where it has gotten too hot and vaporized the electrolyte (Figure 1). Often merely replacing these caps with new ones of the same value will bring a board back to life.