shop talk from my electrical engineering days:

I think my favorite power-related mishap involved the board layout engineer using the wrong DC barrel plug in the layout (center-negative instead of center-positive)

none of us caught it during layout review because we were focusing on the complicated things like the FPGA and the main component

the board is normally powered by USB so everything was testing fine on the first prototypes

until like Friday afternoon when we were like "okay let's make sure the DC power failover works" and we go to plug it in and the fuckin power-source-selection IC pops and leaves a crater

that was fun

@rey

My second internship we had a power supply known as the Trace Breaker. It was a 15V, 50A linear supply that weighed a fucking ton. You'd use it on boards with a short somewhere and ramp the voltage slowly while using a thermal camera. I actually had a board I designed fail and we couldn't break a trace even at max amps, because the PCB shop failed to etch a corner of the board under some connectors! It was a huge power/ground short that was like 20% of a layer. XD

@zetasyanthis @rey for stuff like that, i think an H-field probe is a lot easier to use

if a lot less impressive

remind us to tell you about liquid crystal hotspotting sometime
-F

@Felthry @rey

It might be, but blowing shit up (the usual result of this sort of nonsense) is kinda fun. :P

@zetasyanthis @rey We once put a piece of #30 gauge wire wrap wire across the terminals of an "ultra high current" (capable of up to 1500 A) SMU and programmed it to just do pulses of current increasing until it breaks

it made it to several amps before it just melted
-F

@zetasyanthis @rey this actually had a purpose, believe it or not: we wanted to determine a rough measurement of the fusing current of a similar type of wire

figured this was a good enough approximation so put it in there and let it do its thing

it actually fried the socket we poked it into in the process, which indicates there was a lot of contact resistance
-F

@Felthry @rey

Hopefully the socket wasn't that expensive? XD

@Felthry @rey

And that must have been one hell of an SMU to hit 1500A!

@zetasyanthis @rey you should hear the clunking of the contactor when we turn it on

it can only do very short pulses of 1500 A, of course

It came with banana plug cables with a little mechanism inside the plugs that makes them expand when you twist a collet, to increase contact pressure. they're also on some #6 AWG welding cable instead of the more conventional for banana plugs #14 AWG
-F

@zetasyanthis @rey it's an Agilent N1265A ultra high current unit by the way, hooked up to a B1505A semiconductor parameter analyzer
-F

@Felthry @rey

I miss my lab days now. Maybe one day I'll get back into stuff with them. :(

@zetasyanthis @rey i wish you could get stuff like this without being a big company

but this thing was bought used, at like a 50% discount, and it still cost more than a house
-F

@Felthry @rey

Oh I bet it did. There was a point where a previous employer of mine had about a million bucks of test equipment that I had full run of. It was a blast. FSW26s spectrum analyzers from Rhode and Schwarz, Agilent signal gens, Tek and Agilent oscilloscopes, not to mention multiple Cesium references and cleanup oscillators...

@Felthry @rey

I left that behind when I left defense, and I kinda miss it. I do like being able to sleep at night and consider myself a decent person though.

@Felthry @rey

Nowadays I've got a basic 1000-series scope from Agilent and a BK Precision power supply. I don't have anything to do /with/ them at the moment, but I have them... :P

@zetasyanthis @rey we work for a startup so we don't have *that* much fancy equipment, the 1505 is about the fanciest thing we have

the scope we use is a lecroy ws4104hd, a 1 ghz thing from lecroy that cost $10k because we got it on a deep discount

other stuff in the lab is more pedestrian, there's an hp high-voltage power supply from the 1960s (yes, actually the 1960s, it still works perfectly), a handful of Instek power supplies, a Siglent function generator
-F

@zetasyanthis @rey oh we also have a temperature forcing system that we got for $1k used, plus $1k shipping and two dozen hours or so of repair work and learning how to do plumbing to fix it
-F

@zetasyanthis @rey still doesn't work completely right but it does the job. it's older than we are, so i'm just glad the refrigeration system is still working--i'm pretty sure it's insulated with asbestos so we don't really want to open it up for repairs
-F

@Felthry @rey

I hear that. I've used a few thermal chambers in my time, and the things have always been funky. Whether it's for burn-in testing or temperature swing checks, they're always loud and obnoxious.

@zetasyanthis @rey this wasn't a thermal chamber, it's a more specialty piece of eqiupment. it's got a tiny chamber (maybe 1 L in size) on the end of an articulated arm, that can be lowered over a portion of a circuit board and control the temperature of *just* the DUT by blowing hot or cold air on it

it's a fascinating piece of equipment, and it has quite an astonishinig temperature range--from -80 to +225 °C, nominally. ours doesn't quite reach the low end of that
-F