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Old 04-01-2019, 04:02 AM   #1
retardware
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Exclamation 1960s-1982 smelly caps - polychlorinated biphenyls?

There were a lot of smelly caps in the 1960s to 1982.
These have, respective have developed a very annoying fruity smell over the years.
My personal guess is that the bungs get stiff over time, allowing the PCB contents to gas out.

Notorious are the Sprague Atom, Mallory and some Japanese brands.
These were used mainly for linear power supplies.
I have either removed quite a lot of these from old HP, Tektronix and Japanese products like VTRs and amplifiers manufactured from the 1960s to about 1982, or outright threw away that equipment because I find that smell very ugly and nasty, as it is very sticky (= secondary contamination).

To my knowledge the usage of PCBs in caps has been forbidden internationally 1982.
This coincides with my observation that in post-1982 stuff this kind of smelly caps is not present.

There is little to no information in the web about this topic.
I suspect this is because of the PCBs, a very dangerous substance group.
Characteristic for these is their smell, which can be described as sort of artificially-fruity.
Only very few of these caps were marked with a warning of being PCB containing.

Do you know for signs on caps that can indicate PCB content (or its absence) with certainty?


And, finally my warning:
Remove these caps only at open air - not in a room!
The leads are usually very thick. So when desoldering they get hot and evaporate a lot of that sh!t inside, which then gasses out into your face through the hard and no-longer-tight bungs.
In some cases the caps cans are soldered also, which makes removal with a hot air gun mandatory, leading to extreme emissions. If you do this in a room, you will smell the sh!t for weeks and months. So do not do this!

Last edited by retardware; 04-01-2019 at 04:04 AM..
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Old 04-01-2019, 08:04 AM   #2
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

I always like late 80s early 90s apple boards, when I replace the surface mount caps they smell like a fishy vagina, I actually have come to enjoy the smell which is something you might enjoy too!
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Old 04-01-2019, 09:31 AM   #3
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

The only thing that is a tip off point is high voltage, but this is not definitive.

Seems Nippon Chemi-con came clean on which ones they put PCBs in : https://www.chemi-con.co.jp/e/env/pcb.html

I don't have a scent associated with PCB, what does it smell like for sure? I did come across that fishy nasty scent in one SMT capacitor leaky capacitor job -- but not sure because these are surface mount and should be late 80s-90s and past the PCB problem.

Capacitors however do possibly contain ethylene glycol, which is also poisonous but not nearly as much as polychlorinated biphenyls. Ethylene glycol definitely has a sweet scent, so I'm confused as to tell what is what.
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Old 04-01-2019, 12:45 PM   #4
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

From the NCC webpage linked above:

Quote:
Electrolytic Capacitors and PCB
Electrolyte used for electrolytic capacitors is conductive liquid, and therefore, PCBs are not used in principle because of its insulating properties. Electrolytic capacitors manufactured by Nippon Chemi-Con Corporation and MARCON ELECTRONICS CO., LTD. do not use PCBs regardless of manufacturing year.
Oil, including those containing PCBs is an insulator, used as a dielectric.

In electrolytic capacitors, the electrolyte is a conductor. The dielectric is a layer of aluminum oxide. Therefore electrolytic capacitors, by definition would never use PCBs.

This is basic information. I urge retardware to learn basic stuff like this before jumping to wildly wrong conclusions and posting those wrong ideas.
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Old 04-01-2019, 02:12 PM   #5
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

That is indeed true, electroytics are not using PCBs as their charge mobility carrier.

I was wondering about the large can nonpolar paper/oil impregnated paper capacitors that were meant for motors, power factor correction, and other industrial uses versus little "tiny" ones mounted on... the other PCBs (i.e., printed circuit boards). The large ones, on the other hand, have a risk of fire if they are overheated or damaged due to surges or transients.
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Old 04-01-2019, 02:55 PM   #6
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

Thank you guys for your hints!

@BigTroll:
Yes, I know the fishy smell of Apple mobo caps that emanates when decapping But this is a different smell.

@eccerr0r:
Interesting that Nippon Chemicon seems to be one of the rare few companies that have come clear with the dark secret of PCBs.
Ethylene glycol could be possible, due to its properties; will have to get some to compare to the caps smell.
Its low melting point of -12 degs C leading to condensation in the near vicinity could explain the persistence of the smell after emissions, together with its evaporation point of 197 degs and its vapor pressure.

@PeteS in CA:
It is known that electrolytic caps can contain substantial amounts of PCB, specifically Aroclor 1242.
To ensure workers' safety in the disposal of electrolytic capacitors, the EPA concluded an experiment as early as 1976 which confirmed this knowledge. (link)

So one could argue that electrolytic caps apparently can contain PCBs could be considered as basic knowledge since more than 40 years.

At least I highly doubt that concluding from the fact that Nippon Chemicals did not use PCB in electrolytic caps makes it legitimate to conclude that none of the countless competitors used PCB in his electrolytics.

Of course, there could be other causes for the Aroclor 1242 found by the EPA, like accidental mixing in of other capacitors.
But he EPA report did not say anything about this, so I believe we cannot found a statement like "no electrolytic capacitor has ever contained PCBs" just by wildly assuming that the EPA measurements were wrong or misinterpreted.


Edit:
@eccerr0r:
The general rule with historic oil capacitors like that one pictured is, consider it containing PCB unless you can positively identify it as a non-PCB containing one.
There are several lists compiled by organizations and authorities, for example this long one from Switzerland (40+ pages, German language).

Last edited by retardware; 04-01-2019 at 03:19 PM..
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Old 04-01-2019, 03:12 PM   #7
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

Quote:
Originally Posted by BigTroll View Post
I always like late 80s early 90s apple boards, when I replace the surface mount caps they smell like a fishy vagina, I actually have come to enjoy the smell which is something you might enjoy too!
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Old 04-01-2019, 05:06 PM   #8
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Default Re: 1960s-1982 smelly caps - polychlorinated biphenyls?

Incidentally, the ESR of that 1F 600V cap is still pretty low
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