There's a lot of discussion here about the quality and longevity of electrolytic capacitors, and to read much of it, one would think that these are the most failure-prone of all electronic components, and that any piece of equipment you may have around the house (or lab) that uses them is likely to fail any day now.
I can't really dispute any of this, except to say that this is not my experience at all.
Three pieces of electronic equipment I use every day: my computer (motherboard is about 10 years old), my "good" audio equipment (Technics amplifier, Vector Research tuner, both somewhere between 15-20 years old), and the receiver I use for sound on my computer (an Allied that I bought *used* in 1975).
I have other old elecronic stuff that also works fine.
None of these have had any electrolytics fail, so far as I know. So what gives? Am I just lucky? Did the manufacturers use higher-quality caps than what's commonly used today? (The motherboard ain't anything special--it's an Asus, I think, but I do have extra fans in the enclosure.)
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Found--the gene that causes belief in genetic determinism
I don't think you're lucky. I've almost-50-year-old tube equipment with the original electrolytics that worked just fine.
On the other hand, I have two JVC hall synthesizers, both of whose power-supply electrolytics have leaked, one to the point where they had to be replaced. JVC was aware of this; the caps were apparently from a bad batch of around 30 years ago.
You'd think electrolytics would be highly unreliable, but they generally aren't.
Around 2002 there was a big scandal about it. A Tiwanese company hired an engineer to work for a Japanese company that made electrolyte (the stuff inside the capacitor) with the intention of them bringing their trade secrets back to Tiawan for the new factory the company was opening.
The Japanese were on to the scam, and allowed the engineer to learn everything they needed EXCEPT a preservative for the electrolyte. It was pretty sneaky because the capacitors produced passed every test, but would start to pop open after about 6 months of use.
Almost every company on the island bought from them because their price was around half of the Japanese company. Within a year, everything that contained their capacitors failed.
In the end, besides millions of items being replaced, it taught everyone in the business exactly how long something had to last before people stopped complaining when it failed and just replaced it.
Geoff.
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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
It's not a case of being lucky, for the most part. It's more a case of the equipment that you're talking about, being old. Electrolytics which fail in modern equipment, are almost always in switch mode power supplies, or are post-psu decouplers. The ones that are actually employed in the psu itself, are under enormous stresses from the high frequencies that they have to deal with, and it is essential that in order to minimise failure through self heating, only top quality low ESR high temperature types are used. Unfortunately, such caps impose an increased financial burden on the design, so even if the designer had good intentions when he specced them, the bean counters are likely to demand a cheaper lower specced type is used in the production version.
Add to this that much equipment now is very small, and the caps in question will be further stressed by being specced for the smallest physical size that will do the job, and that often means that the voltage rating will be only a couple of volts above the actual voltage that they have to work at. Now I know that there have been those on here in the past, who have got really worked up about this, saying that if a cap is rated at 10v, then it should work at 10v applied, for ever, without complaint. Maybe. On paper. But any of us who are in the repair business, will tell you that in real life, it just ain't so ...
The old equipment which you have, and which you and others in the thread say has never suffered any electrolytic problems, is not exhibiting anything special. 20 years ago, electrolytics were physically bigger for any given value / voltage rating, so had a bigger surface area to dissipate any heat from. As the equipment was larger in the first place, there was no requirement to compromise on voltage rating to get a cap that would fit in there. The larger internal size also allowed for better air circulation, and a lower overall internal working temperature. Switch mode power supplies were a dim idea for the future, so the caps did not suffer high frequency stress, either.
All of that said, Panasonic / Technics gear suffered for many years with the little purple 10uF decouplers going short circuit, and you would be surprised how many cathode bypass electrolytics in valve (tube) amps, are virtually open circuit, if you take the trouble to check them, and how much it improves the performance, when they are replaced ...
So, in conclusion, I would definitely say that in my daily repair experience, electrolytics are now by far and away, the commonest component to fail, and this, IMHO, is for all of the reasons that I have stated.
"Predicting Operating Temperature and Expected Lifetime of Aluminum-Electrolytic Bus Capacitors with Thermal Modeling"
If you know the operating characteristics and temperature, you can predict the lifetime of an electrolytic capacitor. Note that the above is for "computer grade" electrolytics, which tend to be physically larger than commodity grade PCB mounted electrolytics. Your antique test equipment and hardware probably uses these physically larger capacitors. Were you to substitute typical commodity PCB mount electrolytics into your old equipment, I suspect they will have a short lifetime.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Most of these are likely lacking the part which taxes caps - an SMPS.
All the failures I've had on my domestic equipment has been PS caps - an early S-VHS Panasonic, Videologic DAB tuner, Goodmans FM/AM tuner. But all old enough to possibly be expected. Although I've got a conventional power amp driving the subs which is used every day and was bought in '69 - and has never been repaired. ;-)
I've had problems with two Asus boards lying about CPU temperature and shutting down. Also complaining about a fan failure when it's working. But at least they're cheap. ;-)
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*I don\'t have a solution, but I admire your problem. *
Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.
agree, but it may be worse than just replacing the caps. Most switchers start with a higher voltage. As the capacitance reduces and the series resistance increases, the regulator maintains an average output voltage somewhere near the spec. Problem is that the load electronics cares about the peak voltage too. High voltage spikes can take out all the downstream electronics.
Maybe it doesn't matter when labor costs exceed the cost of a new device, but I think the fun times are coming to an end for those of us who like to buy cheap busted stuff and fix it.
Anybody want to buy a monitor with a logic board killed by 20V overvoltage spikes?
Depends, I think, on the design of the PSU, and how it regulates. I have seen cheapo items where a failed secondary side cap has allowed the 5v rail to virtually double, resulting, as you say, in trashed LSIs downstream. OTOH, I have seen secondary side caps that are in such bad physical condition, being domed, and with the plastic melting back, that no diagnostic tool other than the mk 1 eyeball, was needed to spot them, and when they have been replaced, the item has come back to full and normal working order.
On 8/20/2009 12:35 AM Dave Plowman (News) spake thus:
Well, if you re-read what I wrote, real carefully this time, you'll find that there's at least one thing that most definitely *does* have a SMPS, which hasn't failed yet.
And I have other stuff with SMPSs that haven't failed yet either.
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Found--the gene that causes belief in genetic determinism
It's not that the one unit has an SMPs and another does not. It's that the SMPs in question are designed, like the rest of the unit, to last longer than the warranty, but not much more.
Since most consumers choose soley on price the only concern of everyone is that the units last at least a day longer than the warranty. There is no need for anything else because if it fails, they are not going to buy a different brand or go to a different store because they "felt cheated", they are just going to look for a replacement at the lowest possible price.
Very likey if it is an item which can be shipped, it will be bought from an internet retailer. Being interested in photography, I'm sure you remember all of those mail order scam dealers some of whom are still around, even after ripping off customers for since the 1960's.
Like many of those camera dealers, internet retailers are often the same company using different names.
Geoff.
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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
Replaced 2 shorted 2200uf / 16v axial caps in a McIntosh 2205 just yesterday. They were Euro crap - Rodersteins or some such.
To me it just seems that quality rules but is not always predictable. No doubt McIntosh thought these caps were just fine. 30 years later, the caps fail - I suspect due to the oxidation / tarnish we often see on Euro metals.
I once worked on a Honeywell (Philips-built) defibrillator on which the fuse holders were so crusty and blackened with tarnish they wouldn't even conduct electricity to the fuses they were holding!
Chuckle 2.0. Statistics time. Let's pretend that a large quantity of old electrolytic capacitors were defective. In that case, they would have died long ago, been recycled, leaving only the good electrolytic capacitors. 30 years later, all you see are good working ancient equipment. Not having seen the older blown caps, you might presume that all ancient electrolytics are reliable over a long term.
There's also a question of quantity. There are probably several orders of magnitude more capacitors in today's devices than in yesterdays older equipment. Given the larger number of capacitors, and ignoring the bad electrolyte horror, one might presume that today's caps are little better than garbage due to a high failure rate. However, the failure rate is probably (my guess) the same as it was 30 years ago, it's just that there's more of them today. Wait 30 years, and the survivors will sure be proclaimed the ultimate in quality, when compared to the next generation of molecular or atomic scale electronic devices.
Incidentally, I have a 486DX2/66 and Conner 1Gbyte SCSI HD in my palatial office, running SCO Open Desktop 3.2v4.2 since about 1990. The PS blew up at one point and I've blown 2 CPU fans, but otherwise, it's much the same today as it was 19 years ago. From this evidence, do I deduce that the older motherboards, hard disks, and operating systems are more reliable than today's equivalents?
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Go over to any of the newsgroups, mailing lists or websites dedicated to using tube, as in when they were popular, not modern stuff because "it sounds good" :-) radios.
The first thing anyone will tell you is check the tubes, the second is replace ALL of the capacitors starting with the electrolytics. Electrolytics dry out from lack of use, and there are ways of getting them working again without destroying them, but it is not always successful.
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So David and Jeff, the chance of the devices you mention that are in continous usage still working tomorrow morning is pretty good.
The chances of the identical device having sat for almost 20 years in a closet without being touched is almost nill.
As for Jeff's conclusion, I would say the evidence supports it, which is not proof. On the other hand since the great capacitor disaster of 2002, I would say yes, the modern equipment is not designed with long term longevity in mind.
Geoff.
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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
David, I was referring to devices built after the massive capacitor failure in late 2002. After that people no longer expected indefinite life out of consumer electronics.
That's why there are many Pentuim III and equivalent computers still in use and almost no Pentium IV slightly newer ones.
Geoff.
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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
Anyone who has had thousands of various pieces of equipment across the bench knows about this, but how do you make sense to people who had "Three pieces" that work?
I don't agree that all caps should all be automatically replaced. There are a great many reasons they fail. Any manufacturer has certainly had failures in the production run of some model that either had supplier problems, or a latent quality issue of a specific run of a part that only showed up in a specific circuit or application. In the past, serious manufacturers had a factory authorized service network in order to get specific feedback. Lessons that were learned now allow untouchable offshore facilities to shovel cheap products. Quality control is a major job involving tracking of every part shipment and production change. Aside from that, it is obvious that capacitors have been a long time problem in trying to get costs and size down, make them survive, and design around them. Not all Caps are the same and not all are created equally and some see a harder life than the rest of their kind.
I've just had to change a 16uf 450v electrolytic in my Solartron CO 546 signal generator. It's the first one to dry out since the generator was made in the 1950s but I'm not drawing any statistical conclusions from that.
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~ Adrian Tuddenham ~
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