Anyhow, given that the devices all charge fine on the computer, the problem is almost certainly a defective charger. I strongly advise against using cheap chargers due to safety concerns, so I’d buy a name brand charger (Apple, Anker, Belkin, etc) and destroy the old one.
Srs question. Are the name brand ones really safe, though?
I've understood that all these things come out of the same factories.
Nah, that’s not really true. No manufacturer that courts the likes of Apple and Samsung would dare risk its reputation by making literally lethal products.
Anyhow, the proof of the pudding is in the eating: teardowns of genuine name brand chargers show
enormous differences in construction.
So is a genuine name brand charger safe: absolutely. In fact, the efforts they go to eliminate once-in-a-million failure modes with the potential for human harm are quite surprising. For example, the first generation of Apple’s tiny cube chargers could, in rare cases, come open such that the prongs were left plugged into an outlet, live. Nobody was hurt, but there were a handful of ones that came open. So they recalled millions of them and replaced them with an updated version. And teardowns of the new version basically scream that someone was told “redesign this so that that failure can’t EVER happen, not once in a million, not once in a billion, NEVER.” They certainly wouldn’t entrust this to a power supply company willing to make death traps where only a few microns of lacquer separate the user from mains.
They also recalled a much larger millions of the European one, years later, I forget what for.
With regard to transformer insulation and HV clearances, some are better than others. Can we rely on Apple and Samsung, name branded (and genuine) USB chargers being safe just on brand name alone?
Good question. The answer is: only if bought from an official reseller. The vast majority of Apple and Samsung chargers on eBay, Amazon, etc are counterfeit. But if you buy one directly from Apple, Samsung, a phone carrier store, Best Buy, etc, it’ll be legit.