[Techtalk] Bursting or bulging capacitors :o

Alvin Goats agoats at compuserve.com
Wed Oct 22 13:22:48 EST 2003

Sufficiently high current surges (lightening), reverse polarity (AC
leakage on a DC line, like a diode failure in  the first stage of a
power supply) and sufficiently high overvoltage (spiking from drills,
electric motors, lightening) can also stress electrolytic and tantalum
capacitors. Once overstressed they can slowly deteriorate and bulge (if
you see one bulging, it needs to be replaced FAST before it...) or
explode. Occaisionally, you'll find one leaking a nasty sludge rather
than bulge, so just the same, replace it immediately!

Capacitors store a lot of energy, so when they fail catastrophically,
they release all of that energy at once. The energy on the LARGE
capacitors is often equal to several sticks of dynamite, hence the
amount of damage done and the very loud "boom" coming from them. 

If you decide to replce the capacitor yourself:

Get a thick wired alligator clip and clip one side to one of the
capacitor terminals and the other to a medium to large screwdriver of
any type. Hold the plastic handle of the screwdriver, keep your face out
of a vertical path over the capacitor and touch the tip of the
screwdriver to the other terminal. Don't be surprised by the loud snap,
brilliant arc and possible fusing of the screwdriver tip. If it had a
large charge, some plasma may flash upward and burn your face if you are
over top of the capacitor. Trust me, it is safer to have someone else
change the capacitor for you!


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