Evergreen, Everfoul: the exploding electrolytic capacitor
September 19, 2016
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Talk to anyone active in repairing electronics gear at just about any level and their scapegoat, usual suspect, etcetera, is the bad capacitor. Some repairmen even replace all capacitors before even powering up the equipment at a low, low voltage. Ranking high in the BadCap Top-5 is the electrolytic variant, especially the “can” type in equipment produced between 1950 and 1975 roughly. Not forgetting the Dreadful Tantalums of course from 1980-1995 again roughly. And the Bumblebees, Black Beauties — but noting that these are solid capacitors (well sort of).
It’s easy to think that a good 40 years or so of neglect, drying out, and nasty chemicals developing inside the can are the key factors to make an electrolytic “blow its top” suddenly in 2016, and give newcomers a good scare (and tube technology a bad name) . Due to several failure modes an old can-style electrolytic capacitor may die upon you even if it is operated within its safe voltage range. Live with it. The smell is terrible and one you will not forget easily.

But a brand new can-style electrolytic will also kick the bucket spectacularly when reverse polarized or connected to an excessive voltage. Back in 1947, workers at Daven Laboratories in Newark, USA were startled when an electrolytic condenser (capacitor, Ed.) blew up, “the can hitting the ceiling with the speed of a bullet and paper and foil spiraling upward in a cloud of smoke.” The event was published in a small news item in Radio News magazine edition January 1947, but only after Staff Photographer Walter Steinhard re-produced the blow up realistically with the original cast of parts.
Like today, electronics should be in pictures, right? Do not try this @ home.
Radio News was published in the USA from 1919 to 1948.
Source: RFcafe
It’s easy to think that a good 40 years or so of neglect, drying out, and nasty chemicals developing inside the can are the key factors to make an electrolytic “blow its top” suddenly in 2016, and give newcomers a good scare (and tube technology a bad name) . Due to several failure modes an old can-style electrolytic capacitor may die upon you even if it is operated within its safe voltage range. Live with it. The smell is terrible and one you will not forget easily.

But a brand new can-style electrolytic will also kick the bucket spectacularly when reverse polarized or connected to an excessive voltage. Back in 1947, workers at Daven Laboratories in Newark, USA were startled when an electrolytic condenser (capacitor, Ed.) blew up, “the can hitting the ceiling with the speed of a bullet and paper and foil spiraling upward in a cloud of smoke.” The event was published in a small news item in Radio News magazine edition January 1947, but only after Staff Photographer Walter Steinhard re-produced the blow up realistically with the original cast of parts.
Like today, electronics should be in pictures, right? Do not try this @ home.
Radio News was published in the USA from 1919 to 1948.
Source: RFcafe
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Discussion (12 comments)
David Ashton 8 years ago
http://www.eetimes.com/author.asp?section_id=36&doc_id=1284545
Or, how to scare the hell out of your customers! :-) Tantalums do go wrong as well but usually just short and get hot and burn your board. For pyrotchnics, electrolytics can't be beat!
George Shaiffer 8 years ago
loud reports was enough to convince students to double check polarities before powering up.
One case was moving fast enough to leave a dent in a sheet rock covered wall. I could be three rooms away and the report would startle an entire class. Many topics can be taught others seem to require experience to result in learning.
John Cronin 8 years ago
In looking back at that advice I can now appreciate it more. Back in the days of analog electronics using vacuum tubes (valves) and transisters we would periodically see an exploded capacitor. It wasn't a big problem. Today in comparison exploding capacitors is a big and common problem. I'd be willing to guess it has become the #1 killer of computer system boards. When you look at the modern power supply you will find a very complex and elegant design. There is a lot more current going through todays capacitors than in decades past. You will find a lot of components operating very close to their rated limits. There is no "safety factor." There is little allowance for slightly off-spec components.
Is it time to return to the practice of over designing the parts of a system that handle a lot of power?
inOr 8 years ago
John Cronin 8 years ago
I have seen electronic assemblies where a wire or copper strip was shaped to fit over a high current PCB trace, then soldered to it.
David Ashton 8 years ago
http://www.ti.com/lsds/ti/amplifiers/op-amps/precision-op-amps-support-training.page#pocketref
They give data on trace resistance, self heating and separation. It's a free download (about 8 MB) and has lots of other useful info. BUT it's all in imperial units, being a US book! Worth a look though, might have what you're looking for.
WebMaka 8 years ago
The gist of the situation was that a worker at a Japanese electronic-component company left to work at a Chinese competitor, and took a stolen electrolyte recipe with him. That recipe was in turn stolen by workers there, who then sold it to component manufacturers in Taiwan. The problem is that the version of the recipe that was sold was incomplete, and the resulting electrolyte was unstable in actual use and would vent hydrogen as it decomposed. By the time this was discovered slash figured out, literally hundreds of millions of parts were already in the supply chain and had made it into shipping products.
Electrolytic capacitors using the unstable electrolyte are still in the supply chain, and still giving technicians fits, even now, over a decade later. This would be another example of why it's vitally important to carefully source your parts.
Ben 8 years ago
inOr 8 years ago
David Ashton 8 years ago
inOr 8 years ago
TheEditor 8 years ago
I just did a repair of a 1955 Philips oscilloscope and to my amazement all can electrolytics were A-okay (good ESR etc). Not so for 20-odd fixed capacitor of the tar bomb type, most were 1-megohm or less. Fortunately these clunkers do not explode.