Okay, I seem inordinately pleased by this trivial thing. I guess I am.
We had a big, noisy thunderstorm and the cable box fried. The box and the TV were “off” while it was storming, but of course it’s never really off, it’s pulling quite a bit of electricity whether it’s “off” or “on”, and if you try unplugging it or controlling the power it punishes you for your arrogance by losing its mind and taking at least 45 minutes to re-load all the programming info when its powered back up. Joy. You learn… Thou Shalt Not unplug the cable box, no matter what it draws.
It powered up fine, but no signal to the TV. The thing has an “HD” LED on it, and it was coming on and staying off in about the right proportions as I walked up and down the channels with the remote, so it was clearly “seeing” the input signal, but it was putting out nothing. Tried a few things, even swapping out the cable box (and ITS matching power supply) from another room, it worked fine, so clearly the problem was in the box.
DAYS later, the tech came out, looked at it for a second, heard me say what I’d tried, and went back to his truck to get a “new” (who knows) converter box. He had almost zero interest in the old power supply, and when he saw that the cable for it disappeared into a tangle of wires inside the entertainment gear cabinet his interest went to exactly zero. He plugged up the new one with all the wires outside the cabinet, I assured him I’d connect it properly, and he was gone.
So, later I set about fishing out the old power supply. It was a standard concentric DC power connector, but of course that only makes it convenient to plug in any number of other mis-matched power supplies that might well destroy whatever-it-is you plug it into, it doesn’t give a clue. Still, I wanted to check it. Many of them are near-useless, being for odd voltages like 19 volts or 7.5 volts in an apparent deliberate, even determined attempt to keep them incompatible with anything else, but once in a while you find one that’s 9 volts or 12 volts, generally useful if there’s enough amperage for modern devices… or once in a blue moon there’s one that matches some mini-amplifier, notebook or other device you may already have. I’ve scored some spares that way with a little solder and heat-shrink tubing to swap out the plug.
So, I traced the wire and pulled it out- it was a small brick-on-a-leash type PS, not a wall-wart, I found the label and pointed a flashlight at it, and… 5 volts, 4 amps.
Say, I can USE this one…
Not THAT long ago it would have been near-useless, but these days 5 volts is the standard for anything related to USB or USB chargers, a TON of stuff uses 5 volts, and by far most of it is now drawing amperage that far exceeds the half-amp in the original USB spec, and a fair amount of these devices draw more than any typical USB chargers put out. The Raspberry Pi 3, I’m told (I have two here, but haven’t measured myself) draws 2.1 – 2.3 amps when running full blast and flat-out with adequate cooling and no throttling, the built-in Wifi and Bluetooth fired up, etc. Under 2.5 amps, anyway. 4 amps would be perfect to power one with a USB hard drive attached. I’ll check it with the multi-meter and a couple of other things I have, but it’s probably fine for that use.
Cool. Good deal.
Okay, I seem inordinately pleased by this trivial thing, but when was the last time you got anything at all useful from YOUR cable company? Yeah… me too.
Check those junk power supplies before they go to the recycler, folks, you never know. Good luck.
– Robert the Wombat