Electrolytic Capacitor

Hi!

What happens to Electrolytic capacitor when it fails?
i.e. it acts as open or short?

alok1982 said:

open or short?

Click to expand...

Either extreme is possible, but generally the capacitance falls and the ESR increases with age.

Thanks Alec for your reply!
Generally my worry about age effect. So, ESR of my capacitor will increase, with the fall in the capacitance.

To be more accurate, in the vast majority of cases ESR greatly increases, and capacitance 'may' fall slightly - usually the capacitance is still within tolerance yet the capacitor is totally useless. If you're trying to find faulty electrolytic capacitors then it's ESR you need to test.

tantalum "dry" electrolytics often fail short circuit, but tantalums aren't used much except in military/aerospace equipment. i see the occasional leaky or shorted aluminum electrolytic, but the most common failure is high ESR. my experience has been 85% high ESR, 10% leaky, 3% open circuit, and 2% shorted. they're not exact figures, and that 2% should have "other failures" included. Sprague Atom capacitors with the red epoxy seal usually fail intermittent open circuit. if there's a black ring in the epoxy around the + lead, replace the cap, because the black ring is from an internal high resistance connection, and if it hasn't failed yet, it will soon.