Pixietown

My roommate's LED lights went out, and she traced it down to a bad wallwart. I thought I'd crack it open and see if there's any (electronic) gore.
Nothing on the trace-side of the PCB, nothing seems to have gotten super hot and burnt, unlike that last power supply I opened

And the top looks okay too, except maybe that cap on the left that's clearly on the way out.

(You may spot something else wrong. Hang on to that)

@foone so that's what PC Chips went on to do!

@foone the other capacitor meanwhile is being tracked somewhere in low earth orbit

- struggles not to joke about bulges -

@foone@digipres.club

@julie uwu what's this?

And then I looked at the top of the plastic.

HEY LOOK there's a cap. Or... the can for a cap?
It's stuck to the top, with the electrolytic fluid I assume.

SO YEAH it turns out that weird brown cylinder you've been seeing in the pictures is the capacitor. It actually exploded the can off it, with the can getting stuck on the top of the case.

@foone I recognized it as soon as I saw it in the first picture~

it's also possible this was always like this from the factory. Maybe this cap is just used for smoothing, and it being exploded just meant it did no smoothing. Maybe the other cap was doing the same, and that's why it ended up bulging?

yeah. my knowledge of how caps work is limited (I only took the first semester of EE) but it seems to be between the VCC and GND on the DC side

so probably this thing was just outputting way less smooth DC than it should. Maybe the LEDs have their own caps, or maybe they just flickered like mad?

asking my roommate for updates

@foone they'll be cheap nasty caps and those drivers run hot, they've just cooked out. If you replace them (I'd replace all of them) it'll probably work

okay amazingly, she says it never flickered and never actually died: it just got dimmer.

@foone as the pale blue dot does seen from escape velocity...

so my guess as to what happened:

this cheap cap developed a partially short. It now began passing current through it. This caused it to heat up, boiled the electrolyte, and exploded the can off.

The thing STILL keeps working because now that it's dry, it's a really shit conductor, so only some of the current is going through the sploded-cap, which can no longer boil (and it doesn't get hot enough to ignite). But since some the current is diverted, the lights dim

@foone@digipres.club i've worked on several cheap arcade crane machines from a particular manufacturer for some issue or another, often a stuck relay or something thereabouts, only to notice off to the side that one of the caps on the board has done the exact same thing, leaving a small disk of wrapped fabric and a discarded cover we inevitably find ten minutes later
and every single time, the board is still chugging away so we only ever find them when we're already in there for other issues
i think the most i've found was three caps on a single one of those boards that had all done that, and wouldn't you know it the board was still surviving

@666666t wow!

I would test the resistance (and capacitance) of this exploded cap but I don't have access to my electronic tools at the moment. so into the ewaste bin it goes