Electrolytic capacitor failures

The most common reasons that modern digital electronics devices fail seem to be a bad electrolytic capacitors. Bad electrolytic capacitors cause frequent failures of switch mode power supplies. It seems power supplies are often the weakest link in many modern electronics devices.

Since there is tremendous price pressure on PC’s and other consumer electronics devices, there is great pressure for a low-cost power supply, which often means several things. Low-cost components with limited life are often used, circuit components that might limit secondary failures are left out, and parts are often used at or beyond their ratings, causing poor reliability and short life.

The weakest link in power supply is usually one of the electrolytic capacitors. Usually electronics repair people need to replace more electrolytic capacitors than any other electronic components in electronic repair. The aluminum electrolytic capacitor has a limited life span. This occurs because the electrolyte in the element eventually dissipates. Since electrolytic capacitors are not hermetically sealed, the electrolyte in these capacitor eventually evaporates causing increased ESR which causes increased heating, which causes the safety seal on the capacitor to pop, because if it does not pop, the capacitor explodes. Once these capacitors fail, they can cause all kinds of secondary failures. Why this kind of often failing components are then used? By combining small size and very low cost per unit capacitance, electrolytic capacitors are the only cost-effective choice for high-value applications like power supply filtering in most consumer gear.

The changes in performance over time can be described as follows: Eventually, the capacitance begins to drop off and internal resistance (ESR) starts to increase. The loss in capacitor begins to increase, causing it to heat up more and go bad more quickly. Finally, at the end of the life span, the capacitor enters an open circuit mode as the dielectric dries up. More details can be found at Reliabity of Aluminum Elecrolytic Capacitors document.

The capacitor plague involved the common premature failure of certain brands of electrolytic capacitors used in various electronics equipment, and particularly in motherboards, video cards, compact fluorescent lamp ballasts, LCD monitors, and power supplies of personal computers. The first flawed capacitors were seen in 1999, some bad capacitors were still being sold or integrated into designs as of early 2007. An incorrect electrolyte formula within a faulty capacitor causes the production of hydrogen gas, leading to bulging or deformation of the capacitor’s case, and eventual venting of the electrolyte.


A serious quality control problem is that good and poor quality electrolytic capacitors will often have identical electrical performance when newly fitted. But when the bad capacitors are stressed for a long time with high ripple current in hot environment, their electrical performance changes considerably causing the common premature failure. Most other electronic components which are much less subject to spontaneous failure after assembly.

Criteria for Defining Failures in Aluminum Dielectric Capacitors could be something like this:
1. Considerable changes in capacitance is noticed. A failure is defined as a change in capacitance from the initial capacitance level beyond the specified range. The change is generally ±20% to ±30%.
2. Change in Equivalent Series Resistance (ESR). A failure is defined as the component exceeding the specified range. Usually, this range is 1.5 to 3.0 times the initial value.
3. Change in leakage current. The definition of failure occurs when there is an excess of the specification values.

As you can see measuring the capacitance with a multimeter with capacitance meter functionality does not tell the whole story. It is wise to invest on ESR meter which can test e-caps in or off board. If you like building electronics circuits, you can make your own ESR meter based on An Equivalent Series Resistance Meter plans you can find at http://www.ludens.cl/Electron/esr/esr.html. I have successfully built this circuit and I can tell it works well.

Replacing and reforming electrolytic capacitors was quite common before the current throw-away culture took hold. Some people and companies still repair and replace electrolytic capacitors, but usually it is cheaper to throw broken electronics away than it is to perform preventive maintenance or repair it. To pick electronics that last, look for products that have the longest warranties. Since it is VERY expensive for manufacturers to repair computers and other electronics under warranty, they usually pick parts and de-rating to make sure their product lasts at least as long as the warranty.

Before designing electronics that uses electrolytic capacitors, read Application Guide, Aluminum Electrolytic Capacitors to know how to use them correctly.


  1. RyanE says:

    I suspect the first post is actually blog spam, intended to increase their google search ranking, by linking to their website.

    Good post anyway. I’ve fixed (in the past year) one motherboard, two video cards, and my fridge, all with bad Electrolytic Caps.

    The fridge was my favorite. Only 4-5 years old, I bought it new, the icemaker and water worked erratically for a couple of weeks, then the display stopped working, and the fridge started losing cooling. A couple of hours later, and 2 new caps, it’s good as new.


    • tomi says:

      Some digital TV set top boxes also have the capacitor problem. Here are list of component to change and picture where they are for Handan CV-7700 PVR DVB-C set-top-box
      The same power supply is used on some other Handan models as well.
      Please note that there can be some variations on the component placement on the PSU depending on PSU revision…

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  23. elisa says:

    How can you test electrolytics to find out if they are truly dead?? We have been talking about this on TechXchange:

  24. elisa says:

    Thanks, Tomi!!

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  26. Tomi Engdahl says:

    Specifying Electrolytic Capacitors

    The video preview is a product training module of Kemet’s Specifying Electrolytic Capacitors. The presentation provides an overview of electrolytic capacitors for general purpose and power applications. It describes how to specify electrolytic capacitors according to the design requirements.

  27. Tomi Engdahl says:

    This video show many exploding electrolytic capacitors

  28. Tomi Engdahl says:

    Repairing A Router Plagued By Capacitors

    [psgarcha]’s modem/router comes straight from his internet provider, is on 24/7, and is built with the cheapest components imaginable. Eventually, this will be a problem and for [psgarcha], this problem manifested itself sooner than expected. Fortunately, there was a soldering iron handy.

    [psgarcha] replaced those caps again and added a fan and a small heatsink to the largest chip on the board. This should solve any overheating problems

    Bringing a Router back to life (Modding the Beetel 450TC1 Modem, Fixing bootloop)

  29. Tomi Engdahl says:

    Aluminum capacitor slideshow: Handling heat issues

    The lifetime of an aluminum electrolytic capacitor will be shortened as its temperature increases. For every 10 degrees C decrease in temperature at the hottest spot of the capacitor, its lifetime is essentially doubled, so the lifetime varies exponentially with heat.

    Let’s delve much more deeply into this issue with Vishay’s educational technical presentation

    Your system reliability will strongly depend on keeping the heat down in capacitors.

  30. Tomi Engdahl says:

    Home> Community > Blogs > DesignCon Blog
    How to prevent capacitor failures

    Have you ever owned audio equipment or other electronic products that quit working after several years? Have you ever had one of your designs return from manufacturing test or customer usage due to power delivery issues? Many such failures are due to failure of capacitors in the power delivery network (PDN). It is well known capacitor behavior varies with bias voltage, temperature and product age. If you wish for the electronic products you buy and design to operate properly they should be designed with consideration for these unavoidable effects. Component manufacturers should understand and document these effects for designers and EDA tools should readily apply them in simulations.

  31. Tomi Engdahl says:

    It’s always a capacitor

    Back in 2006 I wrote about how my friend Alan Martin over at Texas Instruments had a saying: “It’s always a capacitor.” This was based on his observance that there is a lot of test equipment that goes bad due to dried out electrolytic capacitors, or failed tantalum capacitors. Alan explained his experiences in a subsequent post.

    Alan’s comments were in regards to electronics. Yet his maxim that “it’s always a capacitor” was proven out when my central air conditioning went out recently.

    Even though the label of the silver capacitor was obscured right at the part number, it did not take long to figure out this was a 5uF/25uF GE capacitor part number 27L33 also known as Trane part number CPT00695. Neither Home Depot nor ACE carry start capacitors in the store.

    Look, we’re engineers. And we know that getting the exact part is better than just close. The straps that hold the capacitors are intended for an exact physical size.

    I figured free shipping was better than expensive shipping. To my amazement, the capacitors came at 10:00 AM Wednesday morning. I had them installed fifteen minutes later.

    Ahhhhhhh it’s cool again.

    This field expedient was a great way to lessen my panic over not having air conditioning. It kept my little office comfortable and the whole house dry. I think everyone south of the Mason Dixon line should have one of these portable AC units in the garage, just in case. It took all the pressure off to get the parts immediately.

    There were all kinds of knock-offs and “replacement” units on the Web. But I wanted a “real” relay made by someone I trusted. Well, Newark Element 14 to the rescue. They had the exact unit, a real Tyco part, in stock. And rather than $60, Newark wants $13.

    I know to replace old capacitors because Alan Martin explained it, “It’s always a capacitor.”

  32. Tomi Engdahl says:

    PCB UV inspection – Find bad capacitors and other problems on a PCB

    This is a very interesting and useful way of spotting bad capacitors and other potential problems on a PCB.
    It won’t work on every PCB out there, but it will work on a great number of them. One big advantage with this method is that it is really cheap; all you really need is a UV black light.

  33. Tomi Engdahl says:

    Failed Capacitors Down Computer Monitor

    When capacitors in a computer monitor’s power supply failed, the problem was obvious. Take a look inside of the AC mains power adapter.

    Aluminum electrolytic capacitors fail. It’s what they do. That’s the bad news. The good news is that when aluminum electrolytic capacitors fail, they’re easy to spot. That was the case when an AC mains power adapter used on a computer monitor failed.

  34. Tomi Engdahl says:

    tantalum-capacitor failures:

    What a cap-astrophe!

    The series resistor prevents uncontrolled thermal runaway from destroying the pellet. I also learned that soldering PCBs at high temperatures during manufacturing causes stresses that may cause microfractures inside the pellet. These microfractures may in turn lead to failure in low-impedance applications. The microfractures also reduce the device’s voltage rating so that failure analysis will indicate classic overvoltage failure.

    Lead frames reduce this stress on the pellet to improve reliability. Pellets without lead frames must be soldered directly to the PCB, thus causing mechanical stress; this stress increases substantially with pellet size. Modern construction techniques for large tantalum capacitors use multiple smaller pellets that connect to a common lead frame. We had all these conditions simultaneously-large pellets, no lead frames, a low-impedance voltage source, and overvoltage failure.

    I had the idea to build a capacitor-postprocessing fixture. Its function was to slowly ramp up the voltage applied to the PCB with enough current capacity to power everything on the PCB but with sufficient internal resistance to limit transient capacitor-clearing fault current. Surprisingly, the postprocessing fixture worked! No failures occurred during postprocessing of the units in stock or those in the field. This finding demonstrated that the series element successfully limited clearing-fault current, assuming that 10 to 20% of the units perhaps would fail.

  35. Tomi Engdahl says:

    Keeping old equipment alive

    De-soldering the 100 µF filter cap and checking it with an ohmmeter told the whole story; it wasn’t a capacitor anymore. Then I thought, “Oh heck, I don’t have any parts, I recycled them in New York.” I could have looked online and ordered a replacement but I wanted to get this repair finished that day if possible.

    Fifty cents bought me a replacement capacitor; but, I spent an hour in the store, more reminiscing than shopping. Then I was on my way marveling at how things go in circles.

    With the capacitor replaced, the power supply worked like a charm and I had my oscillator back. I also had a new place to shop with my grandson for science project components.

  36. tomi says:

    Lots of spam is slowly starting to driving me mad.. over 100 spams every day…
    Does anyone know any good plugins or such to help this?
    On thing I use is configuration that makes the comments only visible after they have been accepted…
    So the spams typically get filtered out in the moderation process.. but it takes time to filter out those few real comments from over 100 spams…

  37. tomi says:

    Thank you for yiur feedback. The amount of spam has increased a lot lately and I start hating dealing with this every day. I have no good solution for that yet.


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