Do electrolytic capacitors blow up when old?

[peter]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

 

[N Cook]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

I would say that generally speaking they heat up before exploding so perhaps
fixing a very low temp thermal fuse to the outside/top of the cap, wired
into the supply rail would help but I somehow doubt a guarantee.
They all should have a vent, like any pressure vessel, but obviously they
don't all or those fail to work. I've seen the bolied electrolyte mess in a
part of a lab and hole in the ceiling where a techie replaced a large ps
one, the wrong way round.

 

[PeterD]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

It's not going to happen.

Happy now?

 

[hr(bob) [email protected]]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

It is fairly important to use them regularly, like once or twice every
couple of months, to keep the internal chemistry formed. The quality
of those old capacitors is probably much better than average, and I
wouldn't worry about them blowing up. You probably wouldn't want to
sit and stare at them for hours at a stretch, but I wouldn't hesitate
to use them like yhou say you do.

 

[Arfa Daily]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

The caps in flashes generally charge via an inverter circuit. Compared to
other types of supply that have electros hanging across the end of them, the
inverter supply is likely to be quite high impedance, and will charge the
caps relatively slowly. This being the case, it is highly unlikely that they
would fail in any 'explosive' way. If they were to fail at all as a result
of being 'woken up' after a long period of slumber, they would most likely
fail short circuit, in which case, the inverter will probably just groan a
bit, and shut down.

Arfa

 

[JW]

It is fairly important to use them regularly, like once or twice every
couple of months, to keep the internal chemistry formed.

By any chance, do you have any cites for that? Thanks.

 

[[email protected]]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

Photo-flash caps are typically "good chemistry" and also typically
charged quite slowly from a relatively LV supply (batteries). Consider
how much energy must be transmitted into those caps from the batteries
before they have enough energy to physically explode. That is not
quite the same as making a bright flash. Not gonna happen. However if
you have rapid recovery mains-supplied flash units, you *may* be able
to make them explode - that would require multiple-failures, however.
Not just the caps failing.

Also keep in mind that most caps "blow up" because they are connected
at the wrong polarity and-or are subjected to a very high over-
voltage. Note "multiple failures" above. Mostly they just short or
heat up and open, or leave a sloppy mess.

Peter Wieck
Wyncote, PA

 

[Meat Plow]

The caps in flashes generally charge via an inverter circuit. Compared to
other types of supply that have electros hanging across the end of them, the
inverter supply is likely to be quite high impedance, and will charge the
caps relatively slowly. This being the case, it is highly unlikely that they
would fail in any 'explosive' way. If they were to fail at all as a result
of being 'woken up' after a long period of slumber, they would most likely
fail short circuit, in which case, the inverter will probably just groan a
bit, and shut down.

I agree. It's not like they are sitting there on a stout rail inside some
1000 watt power amp. Also consider the quality of the cap itself which is
probably pretty high.

 

[hr(bob) [email protected]]

By any chance, do you have any cites for that? Thanks.

I have 44 years of experience at Bell Laboratories, dealing with
reliability and other electronic-related quality issues like
electromagnetic compatibility. I also have done electronics repairs
for 50 years, putting myself thru college doing tv repairs, which I
still do.

I agree 100% with the other posters. If the capacitors were to get
leaky enough to start to heat up internally, they would most likely
load down the power supply and reach a steady-state condition short of
exploding.

Exploding usually results from rapid heating when whatever internal
mechanism exists for releasing the hot gasses does not get a chance to
react due to sudden, rapid heating. If the capacitors are being
charged from a lower voltage - almost always the case - there simply
is not enough energy capability to heat them fast enough to cause an
explosion before the venting can take effect. As I and several other
posters said, those capacitors were not the dime a dozen type
manufactured today.

H. R.(Bob) Hofmann

 

[Sam Goldwasser]

If it's a line powered flash, you can increase the input voltage slowly to
allow the cap to reform after non-use.

This might be more difficult with an inverter type though.

 

[Arfa Daily]

Photo-flash caps are typically "good chemistry" and also typically
charged quite slowly from a relatively LV supply (batteries).

<snip>

I think that the cap he is referring to, is the energy discharge source for
striking the xenon flash tube, in which case, they are not charged from a
low voltage battery supply - rather from a high voltage supply derived from
an inverter circuit, which is itself powered by the low voltage and
impedance batteries.

Given that the (largely) urban myth stories about unused electrolytics
exploding, generally refer to those strapped across high voltage supplies, I
would guess that this is what prompted the OP's question.

Arfa

 

[Sam Goldwasser]

It is fairly important to use them regularly, like once or twice every
couple of months, to keep the internal chemistry formed. The quality
of those old capacitors is probably much better than average, and I
wouldn't worry about them blowing up. You probably wouldn't want to
sit and stare at them for hours at a stretch, but I wouldn't hesitate
to use them like yhou say you do.

Geez, twice a month? I let them sit 5 years and there is no problem,
except a slightly longer initial charge time.

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[William Sommerwerck]

Geez, twice a month? I let them sit 5 years and there is no

problem, except a slightly longer initial charge time.

The electrolytics in electronic flashes do seem to take rather a long time
to recharge the first time they're used after sitting for a while. Whether
this is due to deforming, or completely discharging, I don't know.

My experience in restoring the Polaroid #355 flash is that the electrolytic
caps, though almost 40 years old, are rarely bad.

 

[James Sweet]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

They will blow up if connected backwards to a source of sufficiently high
current, but to blow up in normal use would be extremely unusual, I'd be
much more worried about a meteorite crashing through your roof to kill you
in your sleep than that.

 

[Jeff Liebermann]

They will blow up if connected backwards to a source of sufficiently high
current, but to blow up in normal use would be extremely unusual,

Yeah. That's lots of fun. See videos at:
<http://www.youtube.com/results?search_query=capacitor+exploding&search=Search>
Seems to be a fun thing to do. I couldn't find a video of a large
electrolytic explosion, just the small ones.

I'd be
much more worried about a meteorite crashing through your roof to kill you
in your sleep than that.

Start worrying:
<http://news.bbc.co.uk/1/hi/sci/tech/2218755.stm>
<http://www.xenophilia.com/zb0005.htm>

 

[Heinz Schmitz]

Start worrying:
<http://news.bbc.co.uk/1/hi/sci/tech/2218755.stm>
<http://www.xenophilia.com/zb0005.htm>

Do you remember the insurance company, which
offered every girl with name Mary protection
against the risk of immaculate conception?

Regards,
H.

 

[Jeff Liebermann]

Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?

Dunno. There's quite a bit on the topic of old electrolytic caps in
the cazapitor section of the Repair FAQ at:
<http://repairfaq.ece.drexel.edu/sam/captest.htm>

Photoflash:
<http://repairfaq.ece.drexel.edu/sam/captest.htm#ctpfc>

 

[JANA]

I would not worry about the caps blowing up. I you have good quality
flashes, most likely the caps are properly rated to be very safe. It is very
rare that these caps blow up. Usually they will fizzle out. They are
supposed to have a release.

If a cap was to blow up, the case of the flash should be strong enough to
not break opened or be destroyed.

--

JANA
_____


Electrolytic capacitors sometimes blow up -- due to heat, old age, or lack
of use(?).

I have some old studio flashes used for photography and they contain some
high voltage electrolytic capacitors. I use them once in a long while. But
if they ever blow up, it would be very unpleasant.

Could someone reassure me that it is not going to happen, or suggest a
solution?