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Old 15th Oct 2020, 5:43 pm   #1
G6Tanuki
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Default Tantalised!

Working on my AEL3030 HF transceiver today, there was Snap! Crackle! and Pop! event and a bright orange glow followed by an accompanying plume of acrid smoke and the clack! of a breaker.

One of the inevitable orange 'teardrop' Tantalum capacitors had self-destructed - and while leaning over to see what had happened I inadvertently inhaled a good whiff of the fumes.

Is this likely to kill me? Or significantly shorten my life?

The offending capacitor, according to the manual, was only rated at 16V - and had 13.8V continually across it. I've replaced it with a 50V-rated 105C electrolytic. Thankfully, no other components seem to have been harmed during the conflagration.
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Old 15th Oct 2020, 5:53 pm   #2
paulsherwin
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Default Re: Tantalised!

I doubt if it's done you any harm. You need to get toxic substances into your lungs, which means breathing it for several minutes or taking a very deep breath. We instinctively breathe out after inhaling something nasty unexpectedly.
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Old 15th Oct 2020, 6:00 pm   #3
G6Tanuki
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Default Re: Tantalised!

That's reassuring - though I did have a bout of sneezing a few minutes after sniffing the vapours from the failed Tant.

Inhaled fumes can be nasty: I'm reminded of a family-friend who spent several days in hospital with his veins and arteries hooked-up to some sort of ion-exchange-machine after he inhaled the fumes from MIGging Cadmium-plated steel.
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Old 15th Oct 2020, 6:08 pm   #4
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Default Re: Tantalised!

There's probably more danger from the fumes from the encapsulating epoxy than from tantalum compounds.

Tantalum compounds are not very reactive, they don't interfere with cell chemistry, and they are relatively compatible with the human body. (Unlike cadmium - as your poor friend found out.)
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Old 15th Oct 2020, 6:08 pm   #5
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Default Re: Tantalised!

Quote:
though I did have a bout of sneezing
That is what the marvelous body does, stick stuff to the mucous and if it's no good, expel. Snot is a rather underrated thing.
 
Old 15th Oct 2020, 7:50 pm   #6
Julesomega
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Default Re: Tantalised!

I don't think tants mind working close to their rated voltage as long as the voltage doesn't get there too quickly. Someone here will be able to remind us, what sort of dV/dt is safe? I'm guessing ~10V/ms
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Old 15th Oct 2020, 8:37 pm   #7
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Default Re: Tantalised!

Julesomega is definitely on the right track with the rate of rise of volts on tants. Even the manufacturers suggest that whatever the voltage on them there should be a 50-75% margin especially when used in PSU's. At work we see this on a regular basis in the repairs department, so much so that our engineering department got the manufacturers involved!
A useful link here:

https://sh.kemet.com/Lists/Technical...20PS%20App.pdf

As regards the health issues I doubt just one blowing would do any permanent harm but if the symptoms persist then it would be advisable to consult a doctor.
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Old 16th Oct 2020, 2:48 pm   #8
Maarten
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Default Re: Tantalised!

Quote:
Originally Posted by Julesomega View Post
I don't think tants mind working close to their rated voltage as long as the voltage doesn't get there too quickly. Someone here will be able to remind us, what sort of dV/dt is safe? I'm guessing ~10V/ms
Word on the street is, they do mind. Even electrolytics wear out faster when used within 10 to 20 percent of their limits.

That said, using a 50V electrolytic on a 13.8V line is severe overkill. Especially when replacing a tantalum, ESR is much more important. 50V might be fine, but higher voltages tend to use another electrolyte formulation that has a higher ESR so it's worthwhile looking this up before replacing.
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