Electrolytic Capacitor

[alok1982]

Hi!

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

 

[alec_t]

open or short?

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

 

[alok1982]

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

 

[Nigel Goodwin]

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.

 

[unclejed613]

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.