Is it common for these caps to go bad?

[mitsu2k]

Just wondering how common it is for these types of caps to go bad. I have a couple that are measuring approximately correct (997nF) however a couple of them show signs that they have been pretty warm at some point. I'm replacing them anyway but just wanted to know how common it is for these to maybe act up when hot.

[stj]

Re: Is it common for these caps to go bad?

film caps rarely fail unless you put too much current through them.

[mitsu2k]

Re: Is it common for these caps to go bad?

Good to know. Thank you

[Per Hansson]

Re: Is it common for these caps to go bad?

Actually depending on how they are used in the circuit they can fail quite often.
Sometimes it does not matter (if they are just for EMI purposes).
Other times it matters allot, if they are used as a capacitive dropper.

Dave did a video on this, also some interesting comments in the forum thread there on it, video linked in the first post there:
https://www.eevblog.com/forum/blog/e...acitors-fail!/

[redwire]

Re: Is it common for these caps to go bad?

What makes you think your film caps show signs of heating up?
Normally they don't make much heat, and if seeing high ripple currents they seem to go low value.
It could be parts nearby that are heating them, or the plastics are deforming due to age.

[stj]

Re: Is it common for these caps to go bad?

the resin goes yellow/brown if they run hot.

[CapLeaker]

Re: Is it common for these caps to go bad?

I’ve seen them exploded too.