old electronic devices electrolytic capacitors - Page 1
Forum section: electronics / general

author: classicsamus87
author_rank: Regular Contributor
timestamp: November 06, 2020, 10:52:12 am
content: What is the manufacturers' website for me to clarify doubts about storing old electronic devices that have electrolytic capacitors for a long time but that the electrolytic capacitors do not have depolarization and defects?my friend told me to use 1x per month for 30 minutes otherwise the electrolytic capacitors of the old electronics will depolarize and present problems

author: Gyro
author_rank: Super Contributor
timestamp: November 06, 2020, 12:02:36 pm
content: Most manufacturers's datasheets specify a storage life, but in practice, it isn't very useful for capacitors that have been in use for some time.The following thread covers this exact question - hopefully it isn't the same friend.https://www.eevblog.com/forum/beginners/doubts-about-electrolytic-capacitor/

author: classicsamus87
author_rank: Regular Contributor
timestamp: November 06, 2020, 01:57:12 pm
content: I'm confused because some people say to use it every month, others once a year, other people say every 2 years to turn on the old electronics that have electrolytic capacitors but I need a solid response from the manufacturers but I don't have contact with them

author: Siwastaja
author_rank: Super Contributor
timestamp: November 06, 2020, 02:07:06 pm
content: "use every month" is obvious and total bullshit, completely ridiculous.The problem is, you are not going to get very good and exact data from the manufacturers on this. It will be mostly anecdotal which I think you'll hate to hear.Capacitor manufacturers leave this thing for the product designers to figure out, and the product designers then tend to ignore the problem and leave it to the end users unhandled.Personally, I think the problem is way exaggerated by some. I have seen many elcaps die when overstressed by excessive ripple currents in hot environment, i.e.die in usage, but I have never seen an elcap die after powering up after long storage period. (I don't say it doesn't happen, just I have never seen it.)

author: mag_therm
author_rank: Frequent Contributor
timestamp: November 06, 2020, 04:25:27 pm
content: The first check is that the actual capacitance is in spec. That can be done by using a power supply to bias it, then making an R_C low pass filter and feeding that with audio gen.Then:You might be able to find functions for the DC leakage on one of the major manufacturer's data sheet for similar values and types to your old ones in question.For example one function I obtained was I_Leak  =3* sqrt(C) * V : C in uF ( I think Nichicon High ripple versions)Then power up the old capacitor on a DC supply and take it up to say 80% of its rated voltage over a day.Measure the leakage current. it may drop down over 24 hours or so. ( measure by discharge time with a stopwatch)When stabilized, compare the leakage to the function for a new one.On the old ones, 40 years old I tested like that, all the caps that did not have visual evidence of fluid escaping the seals,had lower leakage than the function. I re-used some of them.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 06, 2020, 05:50:03 pm
content: Note that increased leakage current seldom isn't a problem unless it's such high it causes catastrophic failure through heating.

author: David Hess
author_rank: Super Contributor
timestamp: November 06, 2020, 06:31:03 pm
content: Quote from: classicsamus87 on November 06, 2020, 10:52:12 amUnpowered aging is a problem at high voltage where the impedance is high like tube power supplies, and even there it was not a universal problem.

author: Gyro
author_rank: Super Contributor
timestamp: November 06, 2020, 06:35:57 pm
content: Quote from: Siwastaja on November 06, 2020, 02:07:06 pmAgreed. Manufacturers will give an 'specified' shelf life figure for new parts in storage under specified ambient conditions prior to equipment manufacture, but use cases are far too diverse for them to give a sensible and repeatable figure beyond that.I, like many others, have some really old capacitors in test equipment which hardly ever get powered up. I take the approach of powering them up occasionally on a 'when I remember' basis, not specifically for the electrolytics but for the equipment in general - I think it generally does them good. Warming them up keeps moisture out of PCBs, transformers, exercises fan bearings, help Tantalum bead capacitors last longer etc. I've never had a power supply electrolytic capacitor fail after storage either.Again, like many others, I have electrolytics hidden away in drawers that are 40+ years old, I might occasionally pull one out to use for something but have never seen any problems if they show no physical signs of deterioration. It seems a shame to bin them.There might be some cases where higher initial electrical leakage might be a problem, for instance a coupling cap in a signal path, where it might temporarily interfere with biasing, but the circuit should be designed to cope with the leakage of a brand new capacitor at the limit of its shelf life anyway, I would count that as a design weakness anyway. That would be an exceptional case though, a bit of initial additional leakage in a cold capacitor wouldn't typically be noticeable.

author: tkamiya
author_rank: Super Contributor
timestamp: November 07, 2020, 07:41:11 am
content: There are a lot of myths and folklore going around about electrolytic capacitors.I've been buying and repairing old test equipment and ham radio equipment for years. Some date back to 1970s. Many probably sat unused for decades before it got to me. To this date, I had something like 4 electrolytic capacitors blow. Just recently, I took out a few out of an old Tek scope. Measured it. Capacitance and leakage are well within specification. I think this was from 1990s. These were big power supply filters, too.I don't give any special attention to electrolytic caps. When they blow, I replace, like anything else. Otherwise, they stay in place. I haven't heard of anyone turning stuff on periodically for saving caps either. I don't. Fairly recently, computer maker DELL has a string of failures of caps. They were rated too close to working voltage. So in matter of few years, they started blowing. I've seen a few personally. I consider that a design issue.If you are looking at an old equipment, anything in it can blow at any time. When it happens, fix it. There is no reliable way to prolong the life.

author: mag_therm
author_rank: Frequent Contributor
timestamp: November 07, 2020, 06:52:41 pm
content: Quote from: Siwastaja on November 06, 2020, 05:50:03 pmI refer to experience with MVAR rated oil filled water cooled AC and DC capacitors.They are made in sections.The standard way to check the capacitor was to slowly charge each section with a high potential tester, and measure the leakage current.It is a reliable test. If leakage tester is not available, the self discharge test works too.A new oil filled capacitor often has a DC high leakage and runs hot for an initial period, then the leakage goes low and temperature rise reduces to be within specification..You can search " dielectric polarization index" which is an industry standard dielectric test, similar to the above but more detailed, covered by ISO and IEEE standards.I usually purchase old stock electro and other caps for hobby use from surplus suppliers. Eight here 470 uF 200V and two of 9700 uF 50 V arewaiting for the DC leakage test I mention in earlier post and all are expected to pass.

author: WattsThat
author_rank: Frequent Contributor
timestamp: November 08, 2020, 02:57:51 am
content: Worring about electrolytic caps in consumer electronics is like worrying about... navel lint.The only real world issue that I deal with has already been mentioned, high ripple in high voltage applications. Specifically, large value, high voltage filter caps in ac variable frequency drives. Most manufacturers recommend no more than two years of unpowered storage before reforming is recommended when placing stored equipment back into service. My personal experience has been that the higher the kw rating of the drive, typically over 50kw, the more likely the caps will fail when hit with full ripple current after about 6-7 years of idle storage.https://library.e.abb.com/public/43b21606a20648d79c6c1029f2fc5f48/EN_Capacitor_reforming_instructions_G_A4.pdfThe interesting stuff begins in chapter 2. Page 10. 1 hour of reform time per year of storage time.

author: james_s
author_rank: Super Contributor
timestamp: November 08, 2020, 06:22:14 am
content: The thing to watch for is physical leakage of electrolyte, it makes a big mess when that happens. Some capacitors are much more prone to leaking than others. A sniff test is one of the more reliable methods, if it smells like fish there is a leak that should be dealt with immediately.

author: classicsamus87
author_rank: Regular Contributor
timestamp: November 08, 2020, 11:46:50 am
content: I don’t apply low voltage on electrolytic capacitors, I have video games and crt TVs from the 90s that I want to keep and the information that a friend told me was to use these devices every month for 30 minutes because the electrolytic capacitors on these devices are not new and yes old electrolytics but I look for information from the manufacturers I don't have their email

author: Gyro
author_rank: Super Contributor
timestamp: November 08, 2020, 12:36:24 pm
content: Quote from: classicsamus87 on November 08, 2020, 11:46:50 amLook on the manufacturers' websites, download the readily available datasheets and (if they have any,) app notes. That's all the information you're going to get out of them.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 27, 2020, 01:45:32 pm
content: I try to power up old tube type electronics with a variac over maybe a couple hours.Supposedly this "reforms" the electrolytic caps.I have had non electrolytic caps explode (more like a small firecracker) once in an old DC to AC converter, that was in an old radio.Don't really know what the root problem was since the radio was damaged by someone using the wrong power cord, wrong pinout, had to rebuild the converter.Made a mess in the garage.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 27, 2020, 02:50:48 pm
content: Quote from: Wallace Gasiewicz on November 27, 2020, 01:45:32 pmMight have been the infamous RIFA capacitors. They are plastic film capacitors* made with completely botched manufacturing process so they fail catastrophically after some 10-30 years of storage or operation. It's an interesting story how an assumed "good" brand product can be a total disaster.*) proper modern replacements being self-healing, very long life, very reliable

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 27, 2020, 03:20:50 pm
content: Well if it helps, my Dad's Grundig radio from 1959 was not powered for 10+ years, the other night I finally powered it up.Just plugged it in and turned it on.No Variac, no reforming, just full power.It took 10 seconds to warm up and pulled in a local radio station nice and clear. Oh, and it's a selenium rectifier for the B+, so no slow warm up there.Just adding to the controversy.

author: madires
author_rank: Super Contributor
timestamp: November 27, 2020, 03:32:50 pm
content: I think the idea of a preventive maintenance for electrolytics is about keeping the aluminum oxide layer stable, i.e. the isolation layer. Doesn't matter much for low voltage applications, but might for higher voltages. The manufactures tell you about a max. shelf live to be on the safe side. Based on their specs I'd guess powering on a device with high voltage electrolytics every 6 months could help to keep the oxide layer in shape. Anyway, I have a bunch of old electrolytics from power supplies for audio power amps laying around and they are still in excellent condition, despite not being used for decades, while most of the old blue Philips electrolytics became junk.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 27, 2020, 04:35:24 pm
content: Quote from: Alex Eisenhut on November 27, 2020, 03:20:50 pmIMHO, there's nothing weird about this.People expect old electrolytic caps to explode, but this isn't typical, I think it's more about hearing the stories than actually experiencing problems. I have never seen it happen, personally. I always just plug in the old stuff.Reforming increase the chances of success, maybe from 90% to 95%, but old devices Just Working despite no reforming at all is still the expected result.In audio equipment, the problem with bad electrolytics may be increased hum due to increased ESR and decreased capacitance, and reforming may not help significantly, replacement is often necessary.

author: Gyro
author_rank: Super Contributor
timestamp: November 27, 2020, 06:49:26 pm
content: Quote from: Siwastaja on November 27, 2020, 02:50:48 pmThey're Metallised Paper actually. It gives them a higher dV/dt capability than plastic film types (that's why they are used), they're actually really good capacitors when they're not exploding!Still self-healing (metallisation) but unfortunately, being paper, they are a lot more prone to failure on package cracking and moisture ingress.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: November 28, 2020, 10:42:32 pm
content: About caps exploding;I only had that ONE cap go POP in a regular Ham Radio. It was in DC to AC converter. Dont remember if it was a RIFA, but caps in this application have a very stressful life.Must not have liked me at all.Caps in old RF amps are another story and are used in voltage doublers and triplers and are a bigger problem and can go off sounding more like a firecracker. This happens more often. Voltage is something like 1 KV in old tube RF amps so caps can have 500 V on them. I have worked on these things and have decided it is best just to avoid them.I have seen 100's of old radios start up without a hitch after many years in garages and basements. Most likely problem is not a POP but a 60 cycle HUM from bad electrolytes. Sometimes this is not loud enough for me to hear but drives audiophooles nuts.Some people say that starting old radios with the variac can reform the electrolyte caps so you do not have hum and don't have to replace them. I don't know how true this belief is. Variac is just being careful and possibly saving some PS caps that would fail and make noise. I kinda agree with the 90 to 95% analogy.Most of failures on caps in more modern equipment is easily fixable when the caps go. They are of course much lower voltage. If you get an old piece of equipment, just find a group that uses it and they will tell you what problem caps to look after or replace. RIFA caps are a known problem as pointed out by another poster.I sometimes have trouble starting myself up once a month, hard to remember to plug all this stuff in.

author: james_s
author_rank: Super Contributor
timestamp: November 30, 2020, 09:16:50 pm
content: Quote from: Siwastaja on November 27, 2020, 04:35:24 pmI've never had one explode, but I have encountered a lot of electrolytics in old radios that were completely dried out and open circuit. A much bigger problem is wax paper coupling capacitors, they absorb moisture and become electrically leaky. They probably won't explode either, but you might find that a precious tube fails is degraded by overloading or an unobtanium IF coil burns out.

author: bob91343
author_rank: Super Contributor
timestamp: November 30, 2020, 09:25:51 pm
content: The problem here is in the original question. What we are trying to do is to make a scientific assessment of something that was not considered too important in manufacture. By that, I mean the capacitor maker has no interest in how the products are used and is just trying to make a living building components. You are asking questions that are simply answered by tallying the experiences of others rather than something that can be answered scientifically.Variations in manufacturing processes and variations in applications are too wide to allow a solid answer to the question. If you are worried about it, check operation now and then. If you want to know how often, good luck. A part can fail immediately after test and it can even recover without outside stimulation.If you want to be more certain of operation, use a better part, preferably one with a different failure mechanism.Otherwise we are just accumulating anectodes.

author: GlennSprigg
author_rank: Super Contributor
timestamp: December 01, 2020, 01:33:13 pm
content: This is an interesting question for "Mr. Carlson's Lab" on YouTube.Interestingly, on a few of his videos, he even talks about the importance of 'Mounting Polarity' of NON-Electrolytic caps.This being for the reduction of Noise by mounting them the wrong way. Basically, caps that are wound as a circular Foil,should have the 'outer' part of the coils lead to ground. (If applicable). They often (old caps) have a black mark indicatingthe outer coil end, but he has proven that numerous times, they are labeled incorrectly! (He shows how to check this).Basically, if 'Electrolytics' are old, then just replace them!