11 ms·

Let's Talk About Capacitor Failure

154 points by blakespot 8y ago

jimnotgym 8y ago
I have seen a few electrolytics fail with a bulged top in switching power supplies and valve amplifiers, and once on a graphics card. If you want to see how your old cap is doing 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.
- holy_city 8y ago
  >learn the safe way to discharge them According to one electronics professor (prefaced this with "do not do this at home") - all you have to do is short the leads with a screwdriver. Or really use a resistor and some alligator clips. Of course a screwdriver is easier to handle without touching the leads than those tiny alligator clips...
  - 52-6F-62 8y ago
    Similar experience in film/tv industrial lighting ballasts and heads. Had old techs evangelize that kind of thing. A lot of wacky people in that field. I wouldn’t trust a screwdriver to be safe enough in many of those cases. Some of the caps in those things are massive and hold a charge for ages. I almost killed myself on one thinking there’s no way there would be any charge left after years being stored in an old uninsulated tractor trailer outside. Boy was I wrong. We were demoing some old ballasts—essentially crumpling them before recycling to prevent raiders from seizing the equipment (it happened). Well one coincidentally-aligned swing of the sledge caved the steel chassis in just enough to short a monster cap. The thing exploded on contact. Thankfully those old steel ballasts were tanks and nothing happened. I was sure glad I was insulated at that moment. Kids, am I right? ;P Just want to second what others are saying: don’t toy with those things, and don’t make uninformed assumptions!
    - xondono 8y ago
      It’s also good to remember soakage in this kind of applications. It’s irrelevant in low voltage electronics, but once you get over 1 kV and in the order of tens of mF, you can get some ugly scares.
      - 52-6F-62 8y ago
        Ugly scares, indeed. We did regular high-pot and soak testing. Some of those boxes would give us quite the light show when they went bad. And I mean without a lamp hooked up.
    - trhway 8y ago
      >don’t toy with those things on a much smaller scale - in about 3rd grade at one point we had that game that took off like epidemic in our school and fortunately subsided quickly too - shocking each other (today you'd call it "tazering":), in an open fight kind of like 2 scorpions or sneaking upon, with the capacitors, wall socket charged (220v in USSR) and if i remember correctly of 10-200mkF (like an 1in thick cylinder or a block up to half Rubik cube size). The shock was profound to say the least and according to some literature seems to be crossing into accidentally deadly territory in unfortunate circumstances. Fortunately no injuries/deaths happened. Happy childhood in USSR :) - many things from our childhood one just cant do today anywhere.
      - bdamm 8y ago
        Doesn't the m and k cancel each other out, leaving just F? You must mean µkF == mF?
        trhway 8y ago
        you're right, should have been "uF" (10e-6), thanks. My mistake - i transliterated Russian label "мкФ" ("mkF") which is abbreviation from the Russian word "mikrofarad".
      - MertsA 8y ago
        One thing that makes that capacitor prank significantly safer is that the terminals are so close together so the actual current path through the victim is very unlikely to send any significant current through their heart. Still possible if they touched one terminal to their hand and the other terminal landed on their body or if the victim got one terminal and the prankster accidentally touched the other.
  - HeyLaughingBoy 8y ago
    I've had EE professors do more dangerous things, but I concur. Use a resistor! A big cap with a good charge comes into contact with a screwdriver and well, arc flash injuries (and death) are a real thing. https://www.youtube.com/watch?v=6hpE5LYj-CY https://www.youtube.com/watch?v=6hpE5LYj-CY
  - myself248 8y ago
    A good old-fashioned incandescent lightbulb with alligator clips is lovely. It's self-indicating if there's still work being done. :)
  - jimnotgym 8y ago
    I used to have a film canister with a big resistor in it, and crocodile clip leads for this job. Like I said though, make sure you are confident you know what you are doing. Some tricks, fit the clips entirely with one hand, and put your other hand in your pocket. You are trying to avoid a shock across your heart...
mrguyorama 8y ago
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?
- topspin 8y ago
  The electrolytic cap market supplies a wide variety of quality levels and is permeated by counterfeit products. Ensuring that you actually use genuine components that will perform to spec is very difficult for anything built to a price. The "Dell situation" didn't start or end with Dell.
- jdietrich 8y ago
  The capacitor plague was never fully resolved. There are still a lot of attractively cheap but highly unreliable electrolytic caps on the market. Electrolytic caps represent a substantial proportion of the BoM of most commodity products, so there will always be the temptation to take a chance on off-brand caps. Even crappy electrolytic caps tend to outlive the warranty period and most customers are completely unaware of the issue, so there's very little incentive to spend the extra money on quality caps. In more discerning markets (enthusiast PC components, high-end hifi), Japanese electrolytic caps are a meaningful selling point. https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague
  - jandrese 8y ago
    For that matter a lot of higher end PC components will advertise "no electrolytic caps" or "all solid state caps" as a feature.
- toast0 8y ago
  Samsung had a batch of these too; I suspect it's a combination of iffy suppliers and designing things exactly to the spec. Thermal design feels like it's often glossed over, especially with cables going everywhere and interrupting airflow. On the other hand, if it's common knowledge that everyone overbuilds for tolerances on capacitors, it's easier to not feel bad about putting 95C electrolytic fluid in a can marked 105C if you "know" that it's common to bump up the rating by some factor when ordering parts.
syntaxing 8y ago
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!!
- kevin42 8y ago
  The ESR meter is like magic! I have fixed a ton of discarded electronics by replacing bad capacitors I found with my ESR meter. Several years back I bought a whole lot of broken test equipment dirt cheap and fixed about 75% of it and resold for a nice profit. Almost everything was fixed with new capacitors. A few years back my oven died suddenly. I popped open the cover and went through all the electrolytics with my ESR meter and found a bad one. I had exactly that value in my parts bin, replaced it and the oven worked like new. The total cost of the repair was less than $1.
  - Scoundreller 8y ago
    Any recommended ESR meters?
    - syntaxing 8y ago
      The blue ESR meter is pretty famous [1]. [1] https://anatekinstruments.com/products/fully-assembled-anatek-blue-esr-meter-besr https://anatekinstruments.com/products/fully-assembled-anate...
- blattimwind 8y ago
  Rarely ESR stays in the acceptable range while the actual capacity is widely out of spec.
ahoka 8y ago
https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague A story of industrial espionage, betrayal and an incomplete electrolyte formula.
- blinky1456 8y ago
  'Industrial espionage was implicated in the capacitor plague, in connection with the theft of an electrolyte formula. A materials scientist working for Rubycon in Japan left the company, taking the secret water-based electrolyte formula for Rubycon's ZA and ZL series capacitors[citation needed], and began working for a Chinese company. The scientist then developed a copy of this electrolyte[citation needed]. Then, some staff members who defected from the Chinese company copied an incomplete version of the formula[citation needed] and began to market it to many of the aluminium electrolytic manufacturers in Taiwan, undercutting the prices of the Japanese manufacturers.[1][42] This incomplete electrolyte lacked important proprietary ingredients which were essential to the long-term stability of the capacitors[4][23] and was unstable when packaged in a finished aluminum capacitor. This faulty electrolyte allowed the unimpeded formation of hydroxide and produced hydrogen gas.[36]' Huh, I did not know this was the reason behind it.
  - Gibbon1 8y ago
    I'm nominally in the electronics industry this was a big deal in part because Chinese companies were also feeding counterfeit parts into the supply chain.
- hinkley 8y ago
  This page doesn't talk about it, but what I recall is that the stage was set for this by a move away from a fire retardant (containing bromine) that was linked to developmental disorders. To eliminate the fire retardant, they also moved to a new capacitor chemistry. That would represent a pretty big spike in demand from manufacturers. New product, possibly new partnerships.
  - jandrese 8y ago
c0deR3D 8y ago
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.
- jandrese 8y ago
  One of the things I hate most about electrolytic caps is the failure mode that drips corrosive liquid over your PCB. Not only does it fail, it makes sure to take the rest of the board with it.
sevensor 8y ago
I recommend reading the massively informative comments section.
arcticbull 8y ago
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).
- xondono 8y ago
  The commenters point is that even typical SMT tantalums have leads: - A/B/C/.. type cases have tiny leads going outwards - more modern cases have metal sheet like leads bent down and inwards. The thing is that tantalums capacity density is hard to beat, specially if you are cost-restricted (those polymers are pricey). There’s also a lot of research from NASA about the safety of tantalums, and they actually think they’re fairly safe provided you don’t expose them to voltage ripple (so don’t place them on SMPS)
  - arcticbull 8y ago
    Totally possible I misread it, agreed about the density and ripple, though due to failure mode I’ve always derated them 50% in designs where I’ll derate niobium or (admittedly expensive) polymer 20% to mitigate the risk of thermal runaway.
  - blattimwind 8y ago
    > There’s also a lot of research from NASA about the safety of tantalums, and they actually think they’re fairly safe provided you don’t expose them to voltage ripple (so don’t place them on SMPS) Besides even the shortest over-voltage incidents, Tantalums also don't like high current pulses. Low-ESR power sources with quick ramp ups are a no-no.
    - xondono 8y ago
      Yes, I read a lot about tantalums and their failure modes some years ago because we wanted to set some kind of use policy for our own products. After a lot of research and testing we ended up forbidding the use of tantalums in our designs and taking the cost hit whenever density was an issue. It’s a drastic measure but I think it was the right call, our products were a perfect mixture of all the things that tantalums don’t support well.
ReC757 8y ago
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... 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. 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. After about the hundredth machine, I never wanted to seat a processor again. This was back when processors had hundreds of fragile pins too! It’s likely that those experiences really pushed me towards software development instead of IT. Good times...
- syntaxing 8y ago
  Totally agree! When Samsung first released their flat screen LCD TVs, ours kept failing after two years of usage and was out of warranty. Apparently a bunch of Korean TVs (including LG) had a bad batch of caps from their vendors. Getting it fixed would of cost $300. Buying my own cap and fixing with my dad cost $1. It was a fun bonding experience too.
- MisterOctober 8y ago
  Yep! System board part number 38HRF and equivalents -- if I never see another one of those doggone things, it'll be too soon!
- logfromblammo 8y ago
  I got a few of those Dells for free and re-capped the motherboards with a soldering iron and some desoldering wick. If I recall correctly, the replacement mobos had a chance of having bad caps, too, so re-capping one yourself was the only way to be sure. Bonus: I never had to re-seat any processors or swap out memory.
- rolleiflex 8y ago
  > After about the hundredth machine, I never wanted to seat a processor again. This was back when processors had hundreds of fragile pins too! They still have hundreds of fragile pins. I just bent a few on an AMD Ryzen 7 that got popped out of its socket due to too weak a socket clamp while removing the fan. You know the saying - ‘The future is already here, it’s just unevenly distributed.’ Turns out, it applies to the past, too.
johnnycab 8y ago
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. https://www.avforums.com/threads/yamaha-rxv1700-power-problem.1533016/ https://www.avforums.com/threads/yamaha-rxv1700-power-proble...
- megous 8y ago
  Maybe. Personally, I try to replace caps, when possible, but oftent times I find that real failure is corrosion of the board, I can do nothing about.
lgleason 8y ago
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..........
- cellularmitosis 8y ago
  > The older the capacitor, the more likely this is to happen The funny thing is that due to this capacitor plague of the early 2000's, capacitors which are even older than this have a better survival rate. The plot of failure likelihood over time would be something like a line with a weird bulge in the middle.
laydn 8y ago
If you want your aluminum capacitors to fail less often: - 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 - Use the highest temperature rating capacitor that you can find, if cost is not a concern. - 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. - 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.
- sokoloff 8y ago
  > use the highest voltage rated capacitor that you can find for your target rail I think you meant to say lowest (or you have some other sign negation in that section, or I misunderstand something)
  - laydn 8y ago
    No, I meant highest. For example: If your target rail is 12V, use a minimum of 16V rated capacitor, but prefer a 25V rated capacitor over 16V. This application note has a very detailed explanation of Aluminum capacitor reliability (page 12): http://www.cde.com/resources/catalogs/AEappGUIDE.pdf http://www.cde.com/resources/catalogs/AEappGUIDE.pdf
    - sokoloff 8y ago
      Thanks. I misread the increase in ESR as a governing effect, rather than a secondary effect.
  - deelowe 8y ago
    Nope, higher. Voltage and heat kills electronics. The better the rating, the longer the reliability.
mikestew 8y ago
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 clock 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?
- jackhack 8y ago
  Auto power environments are actually very rough -- 30% (or more!) swings in V+ a nominal 12V system, noise injected by the points opening/closing and the 30,000V coil generating a spark, the old mechanical-switch voltage regulators causing a giant surge, etc. Honestly, it's kind of amazing anything lasts in that world. I go through an in-dash CD player every few years. (source: restored loads of aircooled VWs over the years.)
  - vonseel 8y ago
    I go through an in-dash CD player every few years. Time to splurge on an aux input for your phone?
  - neuralRiot 8y ago
    Don't forget temperatures that can esily go from -20 to 140f, condensation, dust, vibration, chemicals.
eltoozero 8y ago
Tempest 3000 eh? I build Zarjaz Rotary controllers for that thing if you’re interested. ;) Funny story actually...
- blakespot 8y ago
  Sounds like you saw my blog post elsewhere on the site about Tempest 3000, so you surely saw my rotary. I can't recall...do I have a Zarjaz? Maybe an Opal. Hmmmm. Nice game. Rotary or nothing!
tyingq 8y ago
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. 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 :)
cellularmitosis 8y ago
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. 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." https://www.johansondielectrics.com/ceramic-capacitor-aging-made-simple https://www.johansondielectrics.com/ceramic-capacitor-aging-... but that seems very pessimistic. 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).
- cushychicken 8y ago
  You probably see more decline in capacitance just by running an MLCC close to its voltage rating than you do for a decade. Many of the datasheets will show you the derating curve over voltage. Run a 6.3V X5R cap much over 3.3V, and you'll see the effective capacitance decline precipitously - 50% or more.
- Jeema101 8y ago
  I can tell you that most vintage radio and audio guys generally don't bother replacing ceramic capacitors even on 70-80+ year old equipment, so my guess would be 'a long time'.
  - Gibbon1 8y ago
    Most of the time the failure mode is excessive leakage. Which often doesn't cause problems. And ceramic and tantalum capacitors tend to heal if running at more than a few volts. I found a cap on battery backed up memory array that was sucking about 50uA. Putting 5V across it 'fixed it'
  - anyfoo 8y ago
    Just be sure to always, and unconditionally, replace those paper/wax ones, is what I learned.
zepearl 8y ago
Is it true that japanese capacitors are the best? Example ( https://www.hardwaresecrets.com/how-to-identify-japanese-electrolytic-capacitors/ https://www.hardwaresecrets.com/how-to-identify-japanese-ele... ): > Japanese capacitors are notoriously known by their above-the-average quality (good electrolyte and good sealing), 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?". 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)? Thx :)
- syntaxing 8y ago
  Good quality is directly correlated to good QC (quality control). Manufacturing engineers spend a lot of time to define the process. There are different methods such as six sigma (and the associated continue process improvement) to control and detect the rejects. However, to get there requires a lot of upfront cost and manpower which is why it costs more for better quality parts.
  - zepearl 8y ago
    Thx (didn't know about "six sigma") Do you think that maybe the japanese mentality is more "fit" to achieve such precise/high-quality processes and QC than other people/nations/etc... in the area of capacitors? EDIT: > Lean management and Six Sigma are two concepts which share similar methodologies and tools. Both programs are Japanese-influenced,... ( https://en.wikipedia.org/wiki/Six_Sigma https://en.wikipedia.org/wiki/Six_Sigma ) Puah, really, never heard about this stuff - but isn't japanese mgmt structure famous for being complicated (or is maybe just the "formality" of the mgmt being very complicated for europeans?)?
    - 8y ago
grawprog 8y ago
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. 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.
metaphor 8y ago
> I can’t say for sure that I have ever seen an example of a capacitor failure utterly destroying a system. I suspect the author has never encountered the imbalance failure mode of matched-pair capacitors used in high-power weapon systems.
nathanvanfleet 8y ago
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."
londons_explore 8y ago
Capacitors fail either open or short. Failing open will pretty much always not damage any other circuitry. Failing short will usually not damage other circuitry, since usually a fuse will blow or the power supply refuse to start. 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'.
ncmncm 8y ago
This is a treasure hoard. So much accumulated experience on offer, just for the time it takes to read it.
x0 8y ago
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. 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.
crashbunny 8y ago
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. https://spectrum.ieee.org/riskfactor/computing/it/two-capacitors-and-poor-software-design-cause-of-major-nsw-rail-outage-last-month https://spectrum.ieee.org/riskfactor/computing/it/two-capaci...

154 points by blakespot 8y ago

I have seen a few electrolytics fail with a bulged top in switching power supplies and valve amplifiers, and once on a graphics card. If you want to see how your old cap is doing 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.

holy_city 8y ago
>learn the safe way to discharge them According to one electronics professor (prefaced this with "do not do this at home") - all you have to do is short the leads with a screwdriver. Or really use a resistor and some alligator clips. Of course a screwdriver is easier to handle without touching the leads than those tiny alligator clips...
- 52-6F-62 8y ago
  Similar experience in film/tv industrial lighting ballasts and heads. Had old techs evangelize that kind of thing. A lot of wacky people in that field. I wouldn’t trust a screwdriver to be safe enough in many of those cases. Some of the caps in those things are massive and hold a charge for ages. I almost killed myself on one thinking there’s no way there would be any charge left after years being stored in an old uninsulated tractor trailer outside. Boy was I wrong. We were demoing some old ballasts—essentially crumpling them before recycling to prevent raiders from seizing the equipment (it happened). Well one coincidentally-aligned swing of the sledge caved the steel chassis in just enough to short a monster cap. The thing exploded on contact. Thankfully those old steel ballasts were tanks and nothing happened. I was sure glad I was insulated at that moment. Kids, am I right? ;P Just want to second what others are saying: don’t toy with those things, and don’t make uninformed assumptions!
  - xondono 8y ago
    It’s also good to remember soakage in this kind of applications. It’s irrelevant in low voltage electronics, but once you get over 1 kV and in the order of tens of mF, you can get some ugly scares.
    - 52-6F-62 8y ago
      Ugly scares, indeed. We did regular high-pot and soak testing. Some of those boxes would give us quite the light show when they went bad. And I mean without a lamp hooked up.
  - trhway 8y ago
    >don’t toy with those things on a much smaller scale - in about 3rd grade at one point we had that game that took off like epidemic in our school and fortunately subsided quickly too - shocking each other (today you'd call it "tazering":), in an open fight kind of like 2 scorpions or sneaking upon, with the capacitors, wall socket charged (220v in USSR) and if i remember correctly of 10-200mkF (like an 1in thick cylinder or a block up to half Rubik cube size). The shock was profound to say the least and according to some literature seems to be crossing into accidentally deadly territory in unfortunate circumstances. Fortunately no injuries/deaths happened. Happy childhood in USSR :) - many things from our childhood one just cant do today anywhere.
    - bdamm 8y ago
      Doesn't the m and k cancel each other out, leaving just F? You must mean µkF == mF?
      - trhway 8y ago
        you're right, should have been "uF" (10e-6), thanks. My mistake - i transliterated Russian label "мкФ" ("mkF") which is abbreviation from the Russian word "mikrofarad".
    - MertsA 8y ago
      One thing that makes that capacitor prank significantly safer is that the terminals are so close together so the actual current path through the victim is very unlikely to send any significant current through their heart. Still possible if they touched one terminal to their hand and the other terminal landed on their body or if the victim got one terminal and the prankster accidentally touched the other.
- HeyLaughingBoy 8y ago
  I've had EE professors do more dangerous things, but I concur. Use a resistor! A big cap with a good charge comes into contact with a screwdriver and well, arc flash injuries (and death) are a real thing. https://www.youtube.com/watch?v=6hpE5LYj-CY https://www.youtube.com/watch?v=6hpE5LYj-CY
- myself248 8y ago
  A good old-fashioned incandescent lightbulb with alligator clips is lovely. It's self-indicating if there's still work being done. :)
- jimnotgym 8y ago
  I used to have a film canister with a big resistor in it, and crocodile clip leads for this job. Like I said though, make sure you are confident you know what you are doing. Some tricks, fit the clips entirely with one hand, and put your other hand in your pocket. You are trying to avoid a shock across your heart...

mrguyorama 8y ago

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?

topspin 8y ago
The electrolytic cap market supplies a wide variety of quality levels and is permeated by counterfeit products. Ensuring that you actually use genuine components that will perform to spec is very difficult for anything built to a price. The "Dell situation" didn't start or end with Dell.
jdietrich 8y ago
The capacitor plague was never fully resolved. There are still a lot of attractively cheap but highly unreliable electrolytic caps on the market. Electrolytic caps represent a substantial proportion of the BoM of most commodity products, so there will always be the temptation to take a chance on off-brand caps. Even crappy electrolytic caps tend to outlive the warranty period and most customers are completely unaware of the issue, so there's very little incentive to spend the extra money on quality caps. In more discerning markets (enthusiast PC components, high-end hifi), Japanese electrolytic caps are a meaningful selling point. https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague
- jandrese 8y ago
  For that matter a lot of higher end PC components will advertise "no electrolytic caps" or "all solid state caps" as a feature.
toast0 8y ago
Samsung had a batch of these too; I suspect it's a combination of iffy suppliers and designing things exactly to the spec. Thermal design feels like it's often glossed over, especially with cables going everywhere and interrupting airflow. On the other hand, if it's common knowledge that everyone overbuilds for tolerances on capacitors, it's easier to not feel bad about putting 95C electrolytic fluid in a can marked 105C if you "know" that it's common to bump up the rating by some factor when ordering parts.

syntaxing 8y ago

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!!

kevin42 8y ago
The ESR meter is like magic! I have fixed a ton of discarded electronics by replacing bad capacitors I found with my ESR meter. Several years back I bought a whole lot of broken test equipment dirt cheap and fixed about 75% of it and resold for a nice profit. Almost everything was fixed with new capacitors. A few years back my oven died suddenly. I popped open the cover and went through all the electrolytics with my ESR meter and found a bad one. I had exactly that value in my parts bin, replaced it and the oven worked like new. The total cost of the repair was less than $1.
- Scoundreller 8y ago
  Any recommended ESR meters?
  - syntaxing 8y ago
    The blue ESR meter is pretty famous [1]. [1] https://anatekinstruments.com/products/fully-assembled-anatek-blue-esr-meter-besr https://anatekinstruments.com/products/fully-assembled-anate...
blattimwind 8y ago
Rarely ESR stays in the acceptable range while the actual capacity is widely out of spec.

ahoka 8y ago

https://en.wikipedia.org/wiki/Capacitor_plague https://en.wikipedia.org/wiki/Capacitor_plague A story of industrial espionage, betrayal and an incomplete electrolyte formula.

blinky1456 8y ago
'Industrial espionage was implicated in the capacitor plague, in connection with the theft of an electrolyte formula. A materials scientist working for Rubycon in Japan left the company, taking the secret water-based electrolyte formula for Rubycon's ZA and ZL series capacitors[citation needed], and began working for a Chinese company. The scientist then developed a copy of this electrolyte[citation needed]. Then, some staff members who defected from the Chinese company copied an incomplete version of the formula[citation needed] and began to market it to many of the aluminium electrolytic manufacturers in Taiwan, undercutting the prices of the Japanese manufacturers.[1][42] This incomplete electrolyte lacked important proprietary ingredients which were essential to the long-term stability of the capacitors[4][23] and was unstable when packaged in a finished aluminum capacitor. This faulty electrolyte allowed the unimpeded formation of hydroxide and produced hydrogen gas.[36]' Huh, I did not know this was the reason behind it.
- Gibbon1 8y ago
  I'm nominally in the electronics industry this was a big deal in part because Chinese companies were also feeding counterfeit parts into the supply chain.
hinkley 8y ago
This page doesn't talk about it, but what I recall is that the stage was set for this by a move away from a fire retardant (containing bromine) that was linked to developmental disorders. To eliminate the fire retardant, they also moved to a new capacitor chemistry. That would represent a pretty big spike in demand from manufacturers. New product, possibly new partnerships.
- jandrese 8y ago

c0deR3D 8y ago

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.

jandrese 8y ago
One of the things I hate most about electrolytic caps is the failure mode that drips corrosive liquid over your PCB. Not only does it fail, it makes sure to take the rest of the board with it.

sevensor 8y ago

I recommend reading the massively informative comments section.

arcticbull 8y ago

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).

xondono 8y ago
The commenters point is that even typical SMT tantalums have leads: - A/B/C/.. type cases have tiny leads going outwards - more modern cases have metal sheet like leads bent down and inwards. The thing is that tantalums capacity density is hard to beat, specially if you are cost-restricted (those polymers are pricey). There’s also a lot of research from NASA about the safety of tantalums, and they actually think they’re fairly safe provided you don’t expose them to voltage ripple (so don’t place them on SMPS)
- arcticbull 8y ago
  Totally possible I misread it, agreed about the density and ripple, though due to failure mode I’ve always derated them 50% in designs where I’ll derate niobium or (admittedly expensive) polymer 20% to mitigate the risk of thermal runaway.
- blattimwind 8y ago
  > There’s also a lot of research from NASA about the safety of tantalums, and they actually think they’re fairly safe provided you don’t expose them to voltage ripple (so don’t place them on SMPS) Besides even the shortest over-voltage incidents, Tantalums also don't like high current pulses. Low-ESR power sources with quick ramp ups are a no-no.
  - xondono 8y ago
    Yes, I read a lot about tantalums and their failure modes some years ago because we wanted to set some kind of use policy for our own products. After a lot of research and testing we ended up forbidding the use of tantalums in our designs and taking the cost hit whenever density was an issue. It’s a drastic measure but I think it was the right call, our products were a perfect mixture of all the things that tantalums don’t support well.

ReC757 8y ago

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... 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. 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. After about the hundredth machine, I never wanted to seat a processor again. This was back when processors had hundreds of fragile pins too! It’s likely that those experiences really pushed me towards software development instead of IT. Good times...

syntaxing 8y ago
Totally agree! When Samsung first released their flat screen LCD TVs, ours kept failing after two years of usage and was out of warranty. Apparently a bunch of Korean TVs (including LG) had a bad batch of caps from their vendors. Getting it fixed would of cost $300. Buying my own cap and fixing with my dad cost $1. It was a fun bonding experience too.
MisterOctober 8y ago
Yep! System board part number 38HRF and equivalents -- if I never see another one of those doggone things, it'll be too soon!
logfromblammo 8y ago
I got a few of those Dells for free and re-capped the motherboards with a soldering iron and some desoldering wick. If I recall correctly, the replacement mobos had a chance of having bad caps, too, so re-capping one yourself was the only way to be sure. Bonus: I never had to re-seat any processors or swap out memory.
rolleiflex 8y ago
> After about the hundredth machine, I never wanted to seat a processor again. This was back when processors had hundreds of fragile pins too! They still have hundreds of fragile pins. I just bent a few on an AMD Ryzen 7 that got popped out of its socket due to too weak a socket clamp while removing the fan. You know the saying - ‘The future is already here, it’s just unevenly distributed.’ Turns out, it applies to the past, too.

johnnycab 8y ago

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. https://www.avforums.com/threads/yamaha-rxv1700-power-problem.1533016/ https://www.avforums.com/threads/yamaha-rxv1700-power-proble...

megous 8y ago
Maybe. Personally, I try to replace caps, when possible, but oftent times I find that real failure is corrosion of the board, I can do nothing about.

lgleason 8y ago

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..........

cellularmitosis 8y ago
> The older the capacitor, the more likely this is to happen The funny thing is that due to this capacitor plague of the early 2000's, capacitors which are even older than this have a better survival rate. The plot of failure likelihood over time would be something like a line with a weird bulge in the middle.

laydn 8y ago

If you want your aluminum capacitors to fail less often: - 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 - Use the highest temperature rating capacitor that you can find, if cost is not a concern. - 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. - 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.

sokoloff 8y ago
> use the highest voltage rated capacitor that you can find for your target rail I think you meant to say lowest (or you have some other sign negation in that section, or I misunderstand something)
- laydn 8y ago
  No, I meant highest. For example: If your target rail is 12V, use a minimum of 16V rated capacitor, but prefer a 25V rated capacitor over 16V. This application note has a very detailed explanation of Aluminum capacitor reliability (page 12): http://www.cde.com/resources/catalogs/AEappGUIDE.pdf http://www.cde.com/resources/catalogs/AEappGUIDE.pdf
  - sokoloff 8y ago
    Thanks. I misread the increase in ESR as a governing effect, rather than a secondary effect.
- deelowe 8y ago
  Nope, higher. Voltage and heat kills electronics. The better the rating, the longer the reliability.

mikestew 8y ago

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 clock 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?

jackhack 8y ago
Auto power environments are actually very rough -- 30% (or more!) swings in V+ a nominal 12V system, noise injected by the points opening/closing and the 30,000V coil generating a spark, the old mechanical-switch voltage regulators causing a giant surge, etc. Honestly, it's kind of amazing anything lasts in that world. I go through an in-dash CD player every few years. (source: restored loads of aircooled VWs over the years.)
- vonseel 8y ago
  I go through an in-dash CD player every few years. Time to splurge on an aux input for your phone?
- neuralRiot 8y ago
  Don't forget temperatures that can esily go from -20 to 140f, condensation, dust, vibration, chemicals.

eltoozero 8y ago

Tempest 3000 eh? I build Zarjaz Rotary controllers for that thing if you’re interested. ;) Funny story actually...

blakespot 8y ago
Sounds like you saw my blog post elsewhere on the site about Tempest 3000, so you surely saw my rotary. I can't recall...do I have a Zarjaz? Maybe an Opal. Hmmmm. Nice game. Rotary or nothing!

tyingq 8y ago

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. 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 :)

cellularmitosis 8y ago

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. 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." https://www.johansondielectrics.com/ceramic-capacitor-aging-made-simple https://www.johansondielectrics.com/ceramic-capacitor-aging-... but that seems very pessimistic. 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).

cushychicken 8y ago
You probably see more decline in capacitance just by running an MLCC close to its voltage rating than you do for a decade. Many of the datasheets will show you the derating curve over voltage. Run a 6.3V X5R cap much over 3.3V, and you'll see the effective capacitance decline precipitously - 50% or more.
Jeema101 8y ago
I can tell you that most vintage radio and audio guys generally don't bother replacing ceramic capacitors even on 70-80+ year old equipment, so my guess would be 'a long time'.
- Gibbon1 8y ago
  Most of the time the failure mode is excessive leakage. Which often doesn't cause problems. And ceramic and tantalum capacitors tend to heal if running at more than a few volts. I found a cap on battery backed up memory array that was sucking about 50uA. Putting 5V across it 'fixed it'
- anyfoo 8y ago
  Just be sure to always, and unconditionally, replace those paper/wax ones, is what I learned.

zepearl 8y ago

Is it true that japanese capacitors are the best? Example ( https://www.hardwaresecrets.com/how-to-identify-japanese-electrolytic-capacitors/ https://www.hardwaresecrets.com/how-to-identify-japanese-ele... ): > Japanese capacitors are notoriously known by their above-the-average quality (good electrolyte and good sealing), 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?". 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)? Thx :)

syntaxing 8y ago
Good quality is directly correlated to good QC (quality control). Manufacturing engineers spend a lot of time to define the process. There are different methods such as six sigma (and the associated continue process improvement) to control and detect the rejects. However, to get there requires a lot of upfront cost and manpower which is why it costs more for better quality parts.
- zepearl 8y ago
  Thx (didn't know about "six sigma") Do you think that maybe the japanese mentality is more "fit" to achieve such precise/high-quality processes and QC than other people/nations/etc... in the area of capacitors? EDIT: > Lean management and Six Sigma are two concepts which share similar methodologies and tools. Both programs are Japanese-influenced,... ( https://en.wikipedia.org/wiki/Six_Sigma https://en.wikipedia.org/wiki/Six_Sigma ) Puah, really, never heard about this stuff - but isn't japanese mgmt structure famous for being complicated (or is maybe just the "formality" of the mgmt being very complicated for europeans?)?
  - 8y ago

grawprog 8y ago

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. 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.

metaphor 8y ago

> I can’t say for sure that I have ever seen an example of a capacitor failure utterly destroying a system. I suspect the author has never encountered the imbalance failure mode of matched-pair capacitors used in high-power weapon systems.

nathanvanfleet 8y ago

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."

londons_explore 8y ago

Capacitors fail either open or short. Failing open will pretty much always not damage any other circuitry. Failing short will usually not damage other circuitry, since usually a fuse will blow or the power supply refuse to start. 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'.

ncmncm 8y ago

This is a treasure hoard. So much accumulated experience on offer, just for the time it takes to read it.

x0 8y ago

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. 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.

crashbunny 8y ago

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. https://spectrum.ieee.org/riskfactor/computing/it/two-capacitors-and-poor-software-design-cause-of-major-nsw-rail-outage-last-month https://spectrum.ieee.org/riskfactor/computing/it/two-capaci...