If you want your aluminum capacitors to fail less often:<p>- If you are designing the PCB and not repairing, keep them as far away from heat sources as possible. If you're repairing a PCB and the caps are near heat sources, consider isolating them with thermal material<p>- Use the highest temperature rating capacitor that you can find, if cost is not a concern.<p>- Most caps now have a lifetime rating such as (4000 hrs in 85C). This lifetime also has built-in ripple current assumptions, but for a first order approximation, consider using the "longest rated at highest temperature" cap, if cost is not a concern.<p>- Again, as a very rough guideline, use the highest voltage rated capacitor that you can find for your target rail. This is an approximation, because your second goal should be to generally keep the ESR (equivalent series resistance) low, and as the voltage rating increases, so does ESR. Commercial products tend to choose the voltage rating around 1.2x - 1.5x target voltage. Most industrial products that I've seen target a minimum of 2x.
I remember many years ago a bad batch of dell small form factor machines that constantly failed to popped capacitors. It would always be near the power supply where the heat was greatest. I guess in that certain area the capacitors were outside of their operating range...<p>Nevertheless, as a bored 16 year old, I enjoyed ripping apart all the machines and calling the higher level support lines to order replacement motherboards.<p>As time went on, they took my word on if a machine had failed due to this specific issue. I really enjoyed the responsibility and trust. Since I could fix the machines faster than Dells support turnaround, I just asked them to send the parts.<p>After about the hundredth machine, I never wanted to seat a processor again. This was back when processors had hundreds of fragile pins too!<p>It’s likely that those experiences really pushed me towards software development instead of IT. Good times...
<a href="https://en.wikipedia.org/wiki/Capacitor_plague" rel="nofollow">https://en.wikipedia.org/wiki/Capacitor_plague</a><p>A story of industrial espionage, betrayal and an incomplete electrolyte formula.
As others has mentioned, an ESR is the way go for capacitor diagnosis. Usually you can find the capacitor by determining the symptoms. For instance, if the power indicator turns on then off, it's probably near the power supply and filter circuit. That being said, it can get super dangerous repairing old vintage machines since there can be a huge ass capacitor upstream you do not notice. Always discharge your capacitors before you work on them!!
While the limited lifespan of electrolytics is well known, I'm very curious as to the lifespan of the humble yet ubiquitous 0.1uF ceramic disc capacitor. There must be billions of these little buggers in digital electronics, and I've never seen one go bad from age.<p>This site claims "For X7R and X5R the loss is calculated at -2.5% per decade hour and for Y5V it is -7% per decade hour." <a href="https://www.johansondielectrics.com/ceramic-capacitor-aging-made-simple" rel="nofollow">https://www.johansondielectrics.com/ceramic-capacitor-aging-...</a> but that seems very pessimistic.<p>Interestingly, they also claim the ageing of ceramic caps can be reset by baking them at 150C for a couple of hours. Many electronics board could survive this, which seems to imply that a digital board which used exclusively ceramic caps could in theory last ~forever (> 1 human lifetime).
Is it true that japanese capacitors are the best?<p>Example ( <a href="https://www.hardwaresecrets.com/how-to-identify-japanese-electrolytic-capacitors/" rel="nofollow">https://www.hardwaresecrets.com/how-to-identify-japanese-ele...</a> ):<p>> <i>Japanese capacitors are notoriously known by their above-the-average quality (good electrolyte and good sealing),</i><p>Last year I had to buy a new power supply for my PC and some producers mentioned explicitly that they were using japanese capacitors and I just passively accepted it in the same style as "swiss watch"/"french champagne"/"italian pasta"/"german car" (now excluding exhaust system, hehe) ,therefore intrinsecally referring to good quality, but I always wondered "why?".<p>And if it's true that the "best" capacitors are made in japan, is there any special reason (historical, social, because of source materials, etc...) for that or is it just semi-random (e.g. many japanese that were picky discovered that producing high-quality capacitors was just their perfect meaning of life and therefore covered a previously ignored slice of the market)?<p>Thx :)
Part 2 re: Tantalum capacitors always being leaded parts isn't accurate, there are lots of SMT tantalum capacitors. Due to it's status as a conflict material, though, and it's unique extra-fiery failure mode when you exceed it's ratings, I tend to stick with other low-ESR chemistries like aluminum polymer electrolytic, ceramic or niobium oxide (much more stable - 95% less likely to catch fire and non-conflict, similar performance).
I have seen a few electrolytics fail with a bulged top in switching power supplies and valve amplifiers, and once on a graphics card.<p>If you want to see how your old cap is doing<p>1) learn the safe way to discharge them
2) use an ESR meter to test them in circuit. As to the correct ESR, compare a new cap to the one in circuit.
Electrolytic capacitors, even high quality ones, will eventually dry out and fail. The older the capacitor, the more likely this is to happen....sometimes they will last longer even with lots of use but..........
Only slightly relevant to the topic, there was a capacitor failure in Sydney in 2004 that stopped trains on 6 lines during the morning commute causing 100,000 passengers to be stranded and unable to get to work.
Like all complex failures, there was more than one contributing factor, but if the capacitor didn't fail the trains wouldn't have stopped.
<a href="https://spectrum.ieee.org/riskfactor/computing/it/two-capacitors-and-poor-software-design-cause-of-major-nsw-rail-outage-last-month" rel="nofollow">https://spectrum.ieee.org/riskfactor/computing/it/two-capaci...</a>
I have seen an (anecdotal) large amount of capacitors failing in consumer televisions. I recently replaced one in a friend's TV. These capacitors are supposed to have rated lifetimes of roughly the lifetime of the TV, so why are they failing in normal use? Is there another Dell situation, where a big batch had slight issues?
The weirdest capacitor failure i've experienced was after a single speck of dust ended up inside the control panel of one the CNC machines at work. It landed directly on a capacitor that was part of a circuit for the backup emergency stop system. The system refused to power on because it believed the emergency stop was tripped.<p>We ended up bypassing the circuit itself directly in electrical cabinet until we got an electrician in who found the problem capacitor. Luckily the actual e-stop still worked, this was a backup e-stop, I guess, I'm still not entirely sure. We ended up having to replace the entire CNC controller for the machine.
I didn't see it in the article, but one way I'm used to finding bad electrolytic caps that don't "look bad" is to smell them. I imagine there's not a 100% correlation, but the ones I'm used to smell like fish when they leaked.<p>No replacement for real testing/troubleshooting, but it was a good quick/dirty test when I used to repair microwave transmitters for a living. Also got a lot of curious looks while sniffing suspect boards :)
I'm sure many factors go into the life span of a capacitor. The fix for old VW dashboard clocks (at least in our '81 Vanagon): replace the two capacitors. Now, our VW is 37 years old, but it seems to me a <i>clock</i> should be a pretty low-stress environment. Or maybe I'm wrong, I dunno. Why are 40 year old computers still running on original caps, but a 12VDC clock fails in about the same timespan?
Capacitors fail either open or short.<p>Failing open will pretty much always not damage any other circuitry.<p>Failing short will <i>usually</i> not damage other circuitry, since usually a fuse will blow or the power supply refuse to start.<p>For the above reasons, I wouldn't preemptively change capacitors. From an effort point of view, changing them in the unlikely event of a failure is far less than changing them all 'just because'.
This is one of the major reasons, where so many decent electronics are being consigned to the scrap-heap due to the most innocuous reasons and there are avenues available to bring them back to life.<p><a href="https://www.avforums.com/threads/yamaha-rxv1700-power-problem.1533016/" rel="nofollow">https://www.avforums.com/threads/yamaha-rxv1700-power-proble...</a>
I thought this was well known, but maybe just a rumor. But my understanding is that at one point someone who worked for a capacitor company stole the formula for making electrolytic capacitors and started their own company. Unfortunately they didn't quite get it right, and they had what was called "capacitor plague."
Only time I've seen capacitor failure impact a system is on an old (Win XP) motherboard I got recently, most of the aluminium caps near the RAM slots are leaking, and only 1 of 4 slots work.<p>Oh and there was also the 33uf capacitor I put in backwards across 12VDC. Venting failed, and now there's a dent in my ceiling.
> <i>I can’t say for sure that I have ever seen an example of a capacitor failure utterly destroying a system.</i><p>I suspect the author has never encountered the imbalance failure mode of matched-pair capacitors used in high-power weapon systems.
Sometimes, a capacitor's failure also cause invisible damage to other ICs, it's pretty annoying since some ICs can't just use volt-meter to check if it is still functional.