Spent 6 hours chasing a phantom capacitor leak yesterday

Had a power supply that kept tripping the breaker. Measured everything. Voltages looked fine. No shorts. Replaced the bridge rectifier for no reason. Finally noticed a tiny crusty spot under a 470uF cap. That was it. Leaking from the bottom where you can't see it. Replaced it and the breaker stopped tripping. Six hours for one stupid capacitor. Anyone else ever get tricked by a hidden leak like that?

3 comments

3 Comments

kelly_west741mo ago

And the worst part is these modern caps have that rubber bung on the bottom that hides everything until it's too late, right? I've started using a flashlight from underneath the board on every suspect cap now, just to catch that weird discoloration before it drives me crazy. Maybe we need to treat caps like car tires and just replace them all after a certain age no matter what they look like on top.

casey_harris1mo ago

Aren't car tires usually replaced based on tread wear and age, not just a set time?

terry_carter151mo ago

Are we really comparing computer caps to car tires now? Seems like a bit of a stretch if you ask me. A tire blowing out on the highway is a little different than a cap that might or might not bulge after a few years. Most of those old caps work fine for way longer than people give them credit for, and swapping them all out on a schedule just creates e-waste for no good reason. Half the time the issue is a bad solder joint somewhere else in the circuit anyway, not the cap itself.