Updated 1/5/2019

Just kidding, there is no cure.

Tonight one of my friends asked me about their computer monitor flickering. If you pop open your computer case and see capacitors that look like the one in the top left corner, you need to consider replacing that component.

I mentioned capacitor plague so let’s talk about some fundamentals first.

Capacitors are fundamentally two parallel plates that are separated by a material called a dielectric. These parallel plates are usually placed together with the dielectric then rolled into a cylindrical shape. Is that cheating? Nope! It’s space conservation!

Now, this device is connected (normally through a resistor) to a power source. Let’s just say a direct current source for simplicity’s sake. What will happen is electrons will travel to the negative plate of the capacitor and build up. In this way, capacitors are said to store charge. The ability of a capacitor to store charge is related to the voltage applied to the capacitor. The equation that allows us to solve for the capacitance of a capacitor is C=q/v where q is charge given in Coulombs (C). If we wish to calculate the current through a capacitor at a given point in its discharge (or charge!) cycle, we get I(t)= C*dv/dt where we have previously solved for the time rate of voltage change. I’ll go through that in another post.

How do we know the steady state voltage drop across a capacitor? Well, in a steady state DC system, you can treat it as an open circuit. Think about it. Two parallel plates are pretty much the same as two wires that aren’t touching. This is the opposite of an inductor which can be treated as a short circuit for voltage calculations at steady state.

Next, let’s talk about that dielectric. Your dielectric is where an electric field can be maintained for a long period of time. In some ceramic capacitors you’ll find film dielectrics whereas electrolytic capacitors will usually have paper soaked in an electrolyte. This electrolyte brings us back to the topic of this post: the Great Capacitor Plague of the Early 2000s.

Sometime around the year 2000, there was a problem with the electrolyte mix used in capacitors that went into billions of dollars of electronics. If your TV, computer, or other electronic device failed unexpectedly early between 2000 and 2010, that’s probably why. With global markets, one single manufacturer can contaminate the entire world’s supply of one ubiquitous component. As a result, your xbox died an early death.

What did this plague actually do? Well, the capacitance value of the capacitor lowered rapidly over a relatively short span of time. As a result, massive system instability resulted. In power supplies that used these capacitors, voltage values were not as expected. Unexpected voltage cause hardware crashes at best, fires at worst. The most common result was the resistance of the capacitor would increase due to corrosion formation resulting in abnormally large heat production. As a result, the electolyte expanded and caused the vent seals to rupture which protects the rest of the circuit board but destroys the capacitor.

Unfortunately, this entire situation was at least partially to blame on industrial espionage.