back to article 'The capacitors exploded, showering the lab in flaming confetti'

Welcome to the very first edition of “Who, me?” a new Reg column we hope will prove as entertaining as our Friday On-Call tales of tech support gigs gone wrong. In Who, me? we’ll celebrate the times techies stuffed up, the lessons learned and the career consequences. To kick things off, meet “Alvin”, who “In the early '90s …

  1. Anonymous Coward
    Anonymous Coward


    Like coding, where you need to plan for unexpected inputs, so you should with hardware.

    After toasting a ZX Spectrum whilst building some custom breadboard hardware plugged into the expansion bus, I too learnt this lesson.

    Don't plug prototyped electronics into expensive computers without building a very robust isolation circuit between the two, so only voltage limited data signals can ever get thru no matter how bad you screw up your build.

    1. Sorry that handle is already taken. Silver badge

      Re: Isolation

      And don't give your undergrads your most important and irreplaceable piece of office equipment for use as a "prototyping" tool!

      1. Niall Mac Caughey

        Re: Isolation

        Don't give your PC to undergraduates? Undergraduates I can handle!

        In days of old I ran a lab which had a recently-acquired and very expensive robot arm. It was controlled by a very large and complex PCB covered in ICs, all of them soldered in place. It also had external I/O, with optocouplers for the I and relays for the O. The software ran on an Apple II and the pair were connected via a ribbon cable.

        I foolishly took a day off and returned to find that a senior lecturer had demonstrated the I/O features to his class by connecting 230V AC to one of the optocouplers.

        Suffice it to say that it took me a very long time to fix the Apple and the robot itself became a decorative paperweight due to the prohibitive cost of the replacement board.

        1. Anonymous Coward
          Anonymous Coward

          Re: Isolation

          "a senior lecturer had demonstrated the I/O features to his class by connecting 230V AC to one of the optocouplers."

          Hence my suggestion "without building a very robust isolation circuit between the two", where 'very' means however large you think that isolation should be to protect against it, think user stupidity, and then multiply that value by 20!

          1. DropBear

            Re: Isolation

            ...except the extension connector on the back of the Spectrum was gold-plated PCB traces ("fingers") of the CPU's bus, as-is, and building something that would properly galvanically isolate it while still doing bidirectional I/O at 3.5MHz, while not impossible, was at the time not a practical option for 99.999999% of its owners. Anything less would only have been buffering, hopefully protecting against back-driving the bus but not against any "funny" voltages. So what you actually did instead was design stuff carefully and properly the first time*!

            * let's not get into risk multipliers caused by the appropriate PCB-edge connector being unavailable and fabricating your own from two other pieces of PCB comb-slit into flexible-ish individual contacts for each finger, with a bit of wire soldered onto for better-than-PCB-on-PCB contact. Yes, I did get a Kempston joystick interface out of it and yes, I was definitely wearing my brown pants when I first powered the thing up...

          2. Stuart Halliday

            Re: Isolation

            Did have a twat hand over his son's car remote control unit to me.

            He wanted it repaired.

            Every metal transistor in it was exploded out. Every capacitor/resistor cracked in half, etc.

            He thought attaching the pp3 9v battery clip to the live and neutral of the Mains would substitute for a missing battery.

            1. Lotaresco

              Re: Isolation

              "son's car remote control unit ... He thought attaching the pp3 9v battery clip to the live and neutral of the Mains would substitute for a missing battery."

              I take it that the Darwin award still applies if, instead of removing oneself from the gene pool, one removes one's progeny. Darwin-by-proxy?

  2. Shadow Systems

    "Who Me?" should be the RSS feed title as well.

    The RSS feeds for this & the On Call posts should be titled as much to make them easier to find among the regular news.

    I know if it's from "Simon" then it may be one I'm particularly interested in reading, but if it actually described themselves as "On Call", "Who Me?", or (in the case of Mister Dabbs) "For the weekend Sir?" then we could write an email rule to flag them, play the air raid warning siren, & advise all those around us to leave us alone while we got our weekly infusion of silliness. "Don't talk to me, I'm reading Who Me? again." should be a valid defense for when the H&S folks come running to find out why you've strangled another coworker.


    I mean, ummmm... for when you've just come up with a BOFH worthy form of retribution to enact when that nosey coworker three desks over comes trundling past to stick his honker where it doesn't belong.

    *Shifty eyed nervous glances around*

    I mean, ummm, that I would appreciate it if the RSS feeds could begin with the fact that they contain an On Call, Who Me?, or similar recurring article content, the better for me to know that such an article is available for me to eagerly consume.

    *Pure, sweet, & innocent smile*

    "I'm sorry Your Honour, I have no idea where that lake came from & I'm not responsable for the crater in which it formed."

    /runs away as those nice young men in their clean white coats chase after me screaming for me to take my frog pills...

    1. Anonymous Coward
      Anonymous Coward

      Re: "Who Me?" should be the RSS feed title as well.

      And whilst you're at it ...

      Those of us who get the daily email digest (well, me, anyway) would greatly appreciate it if 'On Call' and 'Who, Me?' could be included in the digest articles titles, for much the same reasons as @Shadow Systems highlights ...

    2. Anonymous South African Coward

      Re: "Who Me?" should be the RSS feed title as well.

      Upvoted for RSS feeds.

      Or do El Reg need eyeballs rather?

    3. collinsl

      Re: "Who Me?" should be the RSS feed title as well.

      I hope those frog pills are appropriately dryed...

    4. allthecoolshortnamesweretaken

      Re: "Who Me?" should be the RSS feed title as well.

      "... a valid defense for when the H&S folks come running to find out why you've strangled another coworker.

      Despite possible boni for reducing headcount, you want to watch that. It's habit forming.

      1. Anonymous Custard

        Re: "Who Me?" should be the RSS feed title as well.

        Or better yet, how about a specific feed and/or email with just BoFH, On Call, SFTW and now Who Me? So it can be specifically marked as high importance, must read immediately and a possible solution to get me through until beer o'clock on Friday?

  3. Anonymous Coward
    Anonymous Coward

    All this talk of breadboards...

    I feel like I've wandered into a Talkie Toaster convention!

    Mmmmmmm... toast.

    1. Anonymous Coward
      Anonymous Coward

      Re: All this talk of breadboards...

      Ahh so you're a waffle man!

      1. Headley_Grange Silver badge

        Re: All this talk of breadboards...

        Vero funny.

        1. choleric

          Re: All this talk of breadboards...

          I'm board now.

      2. The Central Scrutinizer

        Re: All this talk of breadboards...

        And I definitely don't want any smegging baps, baguettes or bagels!

      3. Anonymous Coward
        Anonymous Coward

        Re: All this talk of breadboards...

        A waffle man? Perhaps yes, perhaps no. I can't make up my mind.

  4. DainB Bronze badge


    There's nothing in PC, modern or 30 years old, that could have caused this.

    1. Mine's a pint

      Re: Improbable

      Agreed, although we are assuming that the PC was in a sturdy case as used at those times. Still.....

    2. Anonymous Coward

      Re: Improbable

      Really ?

      I've seen some of those 30 year old switch-mode power supply's that could put out more than 20 amps at 12 volts that DIDN'T have over-current protection built -in like those more modern versions !

      1. DainB Bronze badge

        Re: Improbable

        Power socket on your wall can deliver much more and yet on some reason it does not burn down your house every time you plug something into it.

        1. Evil Auditor Silver badge

          Re: Improbable

          DainB, I don't know where you live but power sockets around here are limited to 10, 13 amps. If it's a 400V socket it may deliver up to 16 amps. (For higher currents we are talking about serious hardware.)

          The power supply in my PC could deliver 70 amps @ 12V - enough to roast a few things...

          1. Omgwtfbbqtime

            Re: Improbable @EvilAuditor

            I have a 32A supply in the garage. Comes with SWMBO having one of those new-fangled electrikery cars. I assume its 240v as we only have the one line coming in to the meter.

            1. Evil Auditor Silver badge

              Re: Improbable @Omgwtfbbqtime

              In my garage too, I have a 32A supply (@400V), which I could even upgrade to about 70A if needed. But it's rare to find those in office spaces, powering some PCs.

              1. StargateSg7

                Re: Improbable @Omgwtfbbqtime

                "....n my garage too, I have a 32A supply (@400V), which I could even upgrade to about 70A if needed. But it's rare to find those in office spaces, powering some PCs. ..."

                WHAT THE BLARNEY are you powering?

                That's 12 800 Watts (32 amp) and 28 000 Watts (70 amps) !!! That's the type of energy we use to power our plasma-arc welding systems or our mainframe busses! What exactly is the sort of computer system are you using to need over 12 THOUSAND WATTS+ of power in a small office?

                An old VAX 780 or IBM Zxx series mainframe?

          2. DainB Bronze badge

            Re: Improbable

            And ? How is that contradicts what I said ?

            Hint: your power supply might be able deliver 70A but those 2 mm wide and few microns thick power lines on PCB won't be able to pass them without melting. And that where your roasting typically ends.

            1. HieronymusBloggs

              Re: Improbable

              "those 2 mm wide and few microns thick power lines on PCB won't be able to pass them without melting"

              Having seen many prototype PCBs go up in flames (despite being made of flame-retardent material) I would say that is not necessarily the end of the problem. As has been pointed out, old switch mode power supplies didn't always have reliable current limiting.

              As for 5V being too low to cause a current surge, have you ever used an arc welder?

              1. DainB Bronze badge

                Re: Improbable

                "As for 5V being too low to cause a current surge, have you ever used an arc welder?"

                On a PCI bus ?


                1. Missing Semicolon Silver badge

                  Re: Improbable

                  You forget two things:

                  1) 30 years ago, the science of Switched-Mode power supply design was less advanced than now. Plus, really cheap "offshore" PSU's were often a bit marginal even when not abused.

                  2) Cascading failure. Imagine you connect +12V (or -5V) to +5V, you would fry a lot of components powered from the +5V rail on the motherboard . If they then fail short, the PSU can then go into overload. Or even the PSU itself might not tolerate +12V on the +5V rail. Once caps start failing in the PSU, the high fault currents will start killing semiconductors, which could overvolt or reverse polarity the remaining caps. While there may not necessarily be actual flames, I could well imagine much smoke, and an acrid smell.

                  1. This post has been deleted by its author

                    1. Phil O'Sophical Silver badge

                      Re: Improbable

                      Linear Technology introduced the LT1070, which made it a whole lot easier. Not easy, just easier.

                      I like the TSR 1 and friends, not cheap but really easy. Drop-in replacement for a 7805, no heatsink required.

                  2. PNGuinn

                    Re: "Plus, really cheap "offshore" PSU's were often a bit marginal even when not abused"

                    Y'mean theyr'e not now?

                    I always buy a cheap psu for my computers. One from a reliable manufacturer with decent specs. One that's unlikely to give me weird data errors due to spikes and noise and one with proper protection so that its unlikely to blow up random bits of the machine.

                    Unfortunately, they tend to be somewhat more expensive. Cheap at the price.

                    I can still get a new case complete with psu delivered to my address from halfway round the world by UK distie for around 25 squid. Apart from the lacerated arteries assembling the machine, what else do you think I'd get?

                    >> Thanks - it's the one with the unused first aid kit in the pocket.

                2. HieronymusBloggs

                  Re: Improbable

                  ""As for 5V being too low to cause a current surge, have you ever used an arc welder?"

                  On a PCI bus ?


                  DainB, no matter the rated current of a PSU, if there are large filter capacitors on the output it can supply many times the rated current while those capacitors discharge, even after any upstream short circuit protection has triggered. That is essentially how a spot welder works, so I'll stick to my welder analogy.

                  You have clearly been very lucky with all of your circuit prototyping. My experience has been quite different.

          3. This post has been deleted by its author

            1. DainB Bronze badge

              Re: Improbable

              Or he might as well have been testing his 8-segment indicator driver with 220V AC, or as many idiotic scenarios as you can imagine trying to prove your point, but none of them change the fact that it is improbable that short circuit on PCI bus can turn PC into "either glowing, or smoking, or both."

            2. Robert 22

              Re: Improbable

              That would seem to be a plausible scenario. If 12V ended up on a lower voltage rail, I could imagine the capacitors on the lower voltage rail going. Alternatively, if the computer was old enough, there would have been a negative supply that one could short a positive rail to.

              This reminds me of an experience I had in the early 1980s. My group had acquired a memory expansion board for a Floating Point Systems array processor. Unknown to us, there were slightly different versions of this exact model that differed in the backplane power pin assignments. On being told by the sales guy that "you just plug it in - what's hard about that?" we did just that with seemingly catastrophic results - smoke and, on further investigation, melted PCB traces. Miraculously, we were able to revive it after improvising repairs for the burned traces - it seems that the large current flow that resulted when the negative bias supply on the memory chips became forward biased was distributed over a sufficiently large number of chips to avoid destroying them.

          4. Ian Johnston Silver badge

            Re: Improbable

            The sockets in my house will all do 30 or 40A, for a while, anyway. It's the plugs which limit things to 13A if you haven't had the foresight to replace the fuse with a short length of copper bar.

            1. PNGuinn

              Re: Improbable

              Yeah, had to do that to prevent a meaty arc welder consuming 13 A fuses. (Bit 'o fuse wire soldered across the 13 A fuse to give it a bit more "delay".)

              Worked fine until the welder developed a shorted turn. Took out the 30 A fuse for the ring in the main fuseboard rather than the one in the plug.

              Remember, there's (almost) always something meater further upstream ... £30 A in the consumer unit, 80A or 100 A main service, 400A in the substation ...

              As my first governor used to say "So it steams a bit."

              Reminds me of back in those days in a test gear department ... One of the Test Room boys brought in a bit of kit that "didn't work". I whipped off the plug cover to discover that one of his coworkers had replaced the fuse with a 1 inch length of pot spindle - nylon pot spindle.

          5. Gordon JC Pearce

            Re: Improbable

            > I don't know where you live but power sockets around here are limited to 10, 13 amps.

            No, your sockets are fused at 32A. They are limited by the total resistance of the wiring and impedance of the transformer that feeds your house, so it's safe to say they're limited to a few thousand amps.

            1. terrythetech

              Re: Improbable

              Hmm, electricity suppliers aren't keen on you taking thousands of amps without being warned. That is why they stick a fuse on the feed to the house. Back in the day when I lived in a bedsit we regularly blew the 60A electricity board fuse every winter as we tried to get warm with bar fires. Annoying as it is a call out job to get it replaced :(

              1. psychonaut

                Re: Improbable

                completely possible. i had a machine in not so long ago. it had a powercool 550 watt psu in it.

                the sata power cables were melted, it absolutely stank, the inside of the case had black smoke / scorch marks on it, the sata connectors for the dvd-rw and SSD were burnt to a crisp, they fell to bits in an avalanche of disgusting, smelly, acrid burnt plastic.

                i think what had happened was a layer of dust and crud had built up on one of the sata power connectors over time. its one of the ones that isnt fully moulded, it had little blanks removed on the back of the connector. (for testing the voltage i suppose?). the sata connector was really tight up against the chassis, a mm ish away.

                i think the whole thing shorted through the crud buildup against the case.

                I didn't believe the customer when they told me what had happened, but after seeing it, i was converted. quite spectacular by all accounts when it happened. I'm not sure about massive flames and flying debris across a whole room, but enough to scare the shit out of you. and 30 years ago, PSU's were indeed very different. (for different read "absolute dog shit"), so yeah, why not.

                i now make sure all the psu's i buy dont have those little blanks taken out own the back of the power connectors..... corsair cx 550m's these days.

          6. JeffyPoooh

            Re: Improbable

            EA noted, "...power sockets around here are limited to 10, 13 amps."

            "Limited" isn't quite the right word in this context. A current "limiter" typically means a circuit with effectively instantaneous current limiting action. If you have a current limiter that limits current to 10 amps, then you'll probably be unable to extract 10.5 amps. This doesn't apply to household wiring.

            Fuses are not bad, speed-wise, but can still take SECONDS to open. Magnetically-assisted circuit breakers (Square-D QO series for example) are pretty quick with huge overloads, but can still allow significant overload to remain connected for many seconds. The older thermal breakers are hopelessly inept, taking a Very Very Long Time™ to open. They protect the wiring from catching fire, but will sit there stupidly warming up slowly while you draw 50% over current for perhaps a full minute (YMMV).

            1. StargateSg7

              Re: Improbable

              May I suggest a Varistor (aka Voltage Dependent Resistor) in-between your vital circuits.

              for the bigger cicuits, an entire regulated power supply system with BIG VARISTORS need to be installed.

              I think the SurgeX/Ametek company now sells such beasts. Get the biggest one you can afford. The surge gets shunted into a heat-producing/taking resistor that will survive MULTIPLE big hits!

              There are SMALLER or LARGER lightning fast varistor setups that have microsecond and less switching/shunting speeds but you will pay a FORTUNE for them!

              1. Danny 14

                Re: Improbable

                our UPS tell us we get between 240 and 250, usually 244. the site gets 3 phase.

          7. Jeffrey Nonken

            Re: Improbable

            P=EI. When you down-convert the voltage, you get a proportional increase in amperage to maintain conservation. Minus conversion inefficiencies, ofc.

          8. swm

            Re: Improbable

            I once designed and built a rack of TTL logic powered by a 5v 100 amp (or was it 500 amp - I forget) switching power supply wired with welding cable. I once hot swapped one of the cards without turning off the power and there was a noise like a firecracker - POW! followed by a tinkling sound. Investigation showed that one of the chips had totally exploded down to the pins and sent shrapnel cascading down the rack. Replacing the chip fixed it but I never did figure out why the chip exploded.

            Another time I pulled a large prototype card plugged into an extension card plugged into a NOVA computer without powering down the computer. This succeeded in making the NOVA unusable. I noticed that the -15v power run on the back plane was next to a system bus line so I spend a day replacing all chips in the NOVA that touched that line.

            I was awarded an "ataboy award" for that one: "you collect three ataboy awards and it makes you a leader of man with super powers, the ability to walk on water etc." One "aw shit" wipes out all of the ataboy awards though.

        2. Korev Silver badge

          Re: Improbable

          Taking the UK as an example, 230V * 13A = 2990W. Almost three KW verses a part not designed for it isn't a fair contest.

          1. This post has been deleted by its author

            1. cosmogoblin

              Re: Improbable

              I teach physics, and one common GCSE question is "What is the mains voltage?" The "correct" answer is 230V, if you write 240V you'll lose the mark. Few kids are interested in why it's changed, so I just warn them to ignore their parents if they use the "wrong" value.

              1. hplasm

                Re: Improbable

                The 'correct' answer is a question: Peak or RMS?

              2. tyne

                Re: Improbable

                And that's why the first thing my A Level Physics tutor told me to forget everything I had learnt at GCSE because it was either a lie or an over simplification.

                I was then told exactly the same thing at degree level, seems a perverse way to teach to simplify things to the point they are factually incorrect and then have to "correct" that knowledge at a later date.

                I don't think that I was that unusual as a 15-16 year old that I could understand that there would be shades of grey in the answer to a question. The fact that "Few kids are interested in why it's changed" is wrong on many levels;

                a) The voltage has never changed, just the way it's described and for political reasons.

                b) Your implying that we shouldn't teach kids anything they're not interested in

                Using the new description of 230v +10% -6% or the old one of 240v +/-6%. Gives a range of valid answers and in both cases either 230v or 240v is a perfectly correct answer.

                A system that marks a student down when they have given a perfectly correct answer just because they haven't given the answer the examiner was expecting is broken and not fit for purpose.

                Reminds me of the quote from my boss in my first true engineering job, "Those that can do, those that can't teach...."

                1. Ken Hagan Gold badge

                  Re: Improbable

                  "A system that marks a student down when they have given a perfectly correct answer just because they haven't given the answer the examiner was expecting is broken and not fit for purpose probably being inflicted on your kids right now."


                  1. OzBob

                    Re: Improbable

                    "A system that marks a student down when they have given a perfectly correct answer just because they haven't given the answer the examiner was expecting is...

                    a great primer for some of the ar5eh0le managers you will meet in IT".

                2. Citizen99

                  Re: Improbable

                  "... And that's why the first thing my A Level Physics tutor told me to forget everything I had learnt at GCSE because it was either a lie or an over simplification.

                  I was then told exactly the same thing at degree level, seems a perverse way to teach to simplify things to the point they are factually incorrect and then have to "correct" that knowledge at a later date. ..."

                  One of our degree lecturers said it thus: "We teach you by diminishing deceptions" .

                  I thought it was fair enough, *if made explicit*, for e.g. starting with Newton, which is practicable enough for some purposes, before moving on to Einstein.

                  With you on pointless, ambiguous or not-even-right-or-wrong questions ;-)

              3. Citizen99

                Re: Improbable

                "I teach physics, and one common GCSE question is "What is the mains voltage?" The "correct" answer is 230V, if you write 240V you'll lose the mark. Few kids are interested in why it's changed, so I just warn them to ignore their parents if they use the "wrong" value."

                Is that a 'Physics' question these days ? ... and there was I trying to be open-minded about the dumbing-down of exams ...

              4. Ali 4

                Re: Improbable

                "I teach physics, and one common GCSE question is "What is the mains voltage?" The "correct" answer is 230V, if you write 240V you'll lose the mark."

                Tell that to Northern Powergen. When they retired our original 1954 single phase 25kVa pole mounted 400v to 250v step-down transformer back in 2014 they replaced it with a 100kVa three phase (only 2 phases in use) step down transformer and used the normal tap (250v). So for me up here in Northumberland, the correct answer is 250v (presently reading 242v as it's 6pm and all the neighbours are making tea.

          2. Chris Holford

            Re: Improbable

            13A, but that's just the fuse rating. In the brief interval before the fuse blows (and, possibly, other protective devices in the house wiring trip), the current can exceed that value by a large margin.

          3. Pedigree-Pete

            Re: Improbable

            Hmmm. I thought there was a problem with this.

            "In a DC circuit, the power consumed is simply the product of the DC voltage times the DC current, given in watts. However, for AC circuits with reactance we have to calculate the power consumed differently."

            The example given finds 240v x 5 amps = 205 ish watts so there is a BIG difference.


            Phew, it's a long time since I did this stuff and I still prefer DC.


            The one with the MRGC in the pocket.

      2. I Am Spartacus

        Re: Improbable - disagree

        My team (it wasm't me, gov, honest) blew up a Vax 11/780 not once, not twice, not even three times, but at least 5 times. Digital were confused as to why the unibus terminal interface could keep blowing up. But as it was under warranty, they kept replacing it.

        It was only by chance that I was in the lab one day. Normally, they didn't let us office types in there in case we did something silly and blew up the lab (very probably the case). The lab was connected to the computer by a long length of shielded cable strung between the two building. It seems the guys in the lab had removed the earth wire from a 4 way extension lead because the earth was interfering with the oscilloscopes, and they needed to allow the earth to float high. Then the plugged their terminal in to this, to record results in the database.

        So the terminal floated high (that was the days of CRT terminals, lots of high voltage there).

        So the lines to the VAX floated high. And then it all earthed through the Vax. Blew the Vax up. But the lab didn't know. So they repeated their tests, blithely unaware that they had taken out a very expensive piece of kit.

        When we found out, we had them label the extension lead with "UNEARTHED - NOT FOR COMPUTER EQUIPMENT", which they should have done anyway, but hey, they are boffins, the brights guys in the room , right?

        We decided that we weren't going to tell DEC in case they stuck a bill for failed VAX's on to us!

        1. Timo

          Re: Improbable - disagree

          We let the smoke out of a bunch of lab equipment, many times. I was working at a company that supplied equipment for airplanes, which run at 120V, 400 Hz, and we would have to run our checks from a PC connected by a serial line (120V 60Hz).

          To save money on the 400 Hz system they did not tie the grounds together, and you can imagine what happened. Plug the device under test into 120V 400Hz, then connect the serial port to the device, and nothing would work. Blown serial port. We got really good a replacing plug-in serial boards, because we blew them out so often. Maybe once or twice we would blow a power supply, or in those days pop a fuse. the one 400 Hz power outlet gained a huge note "FLOATING GROUND".

      3. Pedigree-Pete

        Switch mode PSUs or not.

        Puts me in mind of the unfortunate young techie who was filling in for me when our stateside supplier sent a demo unit (in a PC) for an upcoming exhibition here in Blighty.

        No one told him he'd have to flip the switch from 110v to 220-240v.

        Flew across the lab he did.

        I think we were all young techies when we learnt those kinds of lessons. PP

    3. Anonymous Coward
      Anonymous Coward

      Re: Improbable

      > There's nothing in PC, modern or 30 years old, that could have caused this.

      Speaking as one who, in the early 90s, had to install am internal modem (those plastic-encased jobs) in a tower system under a desk, switched on the PC following the rule never to close the case immediately after installing something, because cockily closing the case straight away means it's guaranteed not to work, and saw a large spark emanate from said modem, followed by a definite conflagration, I would say your confidence in equipment and power supplies of 30 years ago is somewhat misplaced.

      I did discover that it is possible to leap from under a desk straight to the wall-mounted fire extinguisher and back under the desk in two easy bounds. But after this episode, I never used internal modems again.

      1. DainB Bronze badge

        Re: Improbable

        How about you explain me how short circuit inside 5V powered chip caused "power surge".

        1. Anonymous Coward
          Anonymous Coward

          Re: Improbable

          6V @ 10A might qualify.

        2. Stoneshop

          Re: Improbable

          How about you explain me how short circuit inside 5V powered chip caused "power surge".


          Switching PSUs take their reference feedback from their most relevant output voltage, in most cases the +5V rail. Load that rail heavily and you'll see the other output voltages go up. Do something silly with the +5V rail, like that chip blowing, and you could well have the PSU go nuts. And given the crap which even today is sold as computer power supplies, never mind 30 years back, I wouldn't bet on some random PSU shutting down in a decent manner without any malodorous and/or acoustic side effects in case of a sudden overload.

          And saying "that's not supposed to happen" will just show that you know shit about designing and building electronics, especially where shaving the last microrenminbi off the BoM is concerned

        3. J. Cook Silver badge

          Re: Improbable

          Putting voltage on the Ground plane does.... interesting things to computers.

          I trashed my old Commodore 128 by putting 9VAC on the ground plane for the CMOS and TTL logic chips, and blew most of them. How did I do this? By putting a RS232 converter on the expansion port upside down....

          And then there's the time that one of the clients for a company I was working for had an electrician who managed to put 208 on the neutral line and blew up (flames and everything!) two brand new computers. Fortunately for the client, the server was on a UPS which merely went into isolation when it saw voltage where voltage ought not to be...

    4. Doctor Syntax Silver badge

      Re: Improbable


      Please keep away from hardware design.

      1. This post has been deleted by its author

      2. DainB Bronze badge

        Re: Improbable

        "Please keep away from hardware design."

        I'm mostly writing autopilot software for self-driving cars these days, much easier and safer than designing hardware.

        1. This post has been deleted by its author

          1. DainB Bronze badge

            Re: Improbable


    5. Chris King

      Re: Improbable

      "There's nothing in PC, modern or 30 years old, that could have caused this".

      You obviously haven't encountered DIY PC's built by the institution itself, or dodgy kit that was foisted on it by a senior academic with a mate who builds computers, and who somehow managed to get himself appointed as exclusive supplier.

      In a previous job, I encountered both - cruddy machines supplied by a nearby university's "Microcomputer Unit" and death-traps built on the cheap by a friend of an academic.

      Think of "Deadly Binders Inc." and you get the general idea. Flames shooting out of power supplies, cables overheating, and the old, old favourite, razor-sharp edges on cases. If you timed it right, the fire would cauterise your wounds.

      1. Stevie

        Re: Flames shooting out of power supplies,

        Everything's funnier with flames. Even the word "flames" is funny.

        From my own Grand Prix Des Idiots Blithering:

        In the pursuit of Science I attached a lit cigar to the hose of a working Electrolux cylinder vacuum cleaner. The glowing core of the cigar burned down the wrapper in a fraction of a second, disappeared up the hose and set fire to the dust in the bag. Flames shot out of the exhaust and singed the carpet and wallpaper, earning me a damn good thrashing when dad got home.

        Now tell me that you didn't start laughing at the "flames shot out" part. Without the flames it isn't funny.

        1. This post has been deleted by its author

          1. Stevie

            Re: turning the vacuum cleaner into a blast furnace


            Busted for reading El Reg during office hours. Your work here is done, Symon.

        2. Anonymous Coward
          Anonymous Coward

          Re: Flames shooting out of power supplies,

          I attached a lit cigar to the hose of a working Electrolux cylinder vacuum cleaner.

          I know someone who tried to de-odourize a vacuum cleaner by spraying air freshner into the hose while it was running. When the butane propellant reached the motor brushes there was a load 'pop', flames, and a spontaneous diassembly of the dust bug & contents.

    6. Stuart Castle Silver badge

      Re: Improbable

      Having had to deal with a SCSI ribbon cable catching fire when plugged in to the motherboard, and having seen motherboards fry because someone plugged a dodgy card in to them (even a perfectly healthy card plugged in incorrectly can blow a motherboard), I would tend to disagrree. Regarding the hard drive, it's also entire possibly that a faulty motherboard could take that out. All it would take is for the drive interface (be it SCSI, SATA or IDE) to wack a voltage up the wrong wire, and it could easily fry the drive electronics..

    7. Anonymous Coward
      Anonymous Coward

      Re: Improbable

      Me thinks this tells us more about your PC knowledge than what actually happened.

    8. Ernie Mercer

      Re: Improbable

      I'm a retired engineer with experience in analog and digital design. This scenario makes no sense to me.

    9. 9Rune5

      Re: Improbable

      It has been a long time since I dabbled with (very simple) breadboard designs, so I won't comment on that aspect.

      However, about 15 years ago, there was a loud "pop" (or maybe "bang") from my computer that was standing on my desk, with black smoke emanating from its floppy drive. I unplugged it and we evacuated the room. After only a few hours of venting out the room, the smell of burning electronics was nearly gone and we felt reasonably safe to resume operation. My little 3.5" floppy drive however was clearly pining for the fjords. IIRC we replaced the PSU and ditched the floppy drive, and my PC was operational again (I do not remember exactly what we had to replace, but we were operating on a tight budget and I do not think we would have forked out for a brand new computer)

      My point is that if the standard components found in PCs at the time, could do all that relatively unprovoked, then I have no problems believing things could turn really ugly if you poke the monster's eye with a sharp stick.

      Besides, computers are scary. There are tons of documentaries on this subject: "War games", "Terminator" (1 through 4) and The Fly.

  5. Anonymous Coward
    Anonymous Coward

    Our transition from Windows 2000 to XP

    came about because, although the W2000 installation CD had a visible hairline crack, it hadn't, hitherto, inhibited successful installation.

    However, this day, the cd span at ever higher speed, with a juddering overtone. The volume of speeding cd drive and juddering rose until there was a shockingly loud noise like a gunshot, and suddenly the room was filled with pungent dust. The installation CD was history, and so was the drive. PC perfectly happy.

    1. Anonymous South African Coward

      Re: Our transition from Windows 2000 to XP

      Can attest to that.

      Got a client with a W2k install, and needed to do an installation on their server. Opened the CD tray only to find it full of W2K CD shrapnel.

      Decided to toss that CD-R drive and install a new CD-R drive rather...

  6. Daytona955

    It being far in the past, I can now confess that, in a Nuffield A-Level Physics lesson using a bunch of plastic encased electronics modules, I connected the largest electrolytic I could find across the bench supply as a smoothing capacitor, with the polarity 'accidentally' reversed. It was quite spectacular.

    Sorry Mr. Leggett...

    1. Aladdin Sane

      polarity 'accidentally' reversed

      I thought you could only do that to the neutron flow?

    2. BebopWeBop

      Doing physics as well, and having 'hear rumours', we built a couple of very good 'spud cannons' that powered by the rapid discharge (ahem) of a very large capacitor - 1 Farad (if I remember 39 years later) we could engage in duels over quite a distance.

    3. Anonymous Coward
      Anonymous Coward

      "connected the largest electrolytic I could find across the bench supply "

      I did that once with a pencil. After trying various small dc voltages ( <=30v )

      I then tried 240 AC. The wood sort of vaporised leaving a graphite stick!

      1. Daytona955

        Drawing an arc between pencil leads was fun too. Haven't done that for years. Probably a bit anti-social these days as I expect it would splat all the r.f. connections we so depend upon now >)

    4. Jamie Kitson

      > Sorry Mr. Leggett...

      Surely it was you that was leggingett.

    5. Stoneshop

      There was the student on the lab bench opposite mine, who wasn't aware of what the ridge and the '+' markings on an electrolytic cap were meant to convey. With the working voltage for the circuit being 150VDC, for reasons I can't remember any more (no, it didn't involve vacuum tubes). So, a couple of seconds after powering on, there was an almighty bang, a rather pungent, acrid smell and a very pale student.

      1. Anonymous Coward
        Anonymous Coward

        "a rather pungent, acrid smell..."

        Do you remember if it emanated from the remains of the capacitor, or the undercrackers of said student?

    6. ectel

      Sorry Mr. Leggett...

      Was that Headingham School?

      1. David 132 Silver badge

        ectel Sorry Mr. Leggett...

        Was that Headingham School?

        Those who remember a certain Mr Fisher teaching Physics at the Kings School Chester circa 1990 will be chuckling at this point.

        1) Teachers shouldn't fiddle absent-mindedly with large capacitors while teaching,

        2) certainly not ones that have been charged from the bench 12v supply,

        3) and when the inevitable happens and the fly leads make (loud, sparky, shocky) contact, said teacher should have the presence of mind not to say "FUCK" very loudly in front of 25 wide-eyed, innocent and hitherto uncorrupted boys who had of course NEVER heard such naughty words before or used them.

      2. Daytona955

        No, RGS High Wycombe. Early 70s.

    7. Anonymous Coward
      Anonymous Coward

      In my college course, only the first one was accidental.....

    8. Solmyr ibn Wali Barad

      Tiny diodes, when connected straight across mains, tend to disintegrate with nice light effects. Who knew?

      (not me, I wasn't there)

      1. John Brown (no body) Silver badge

        "Tiny diodes, when connected straight across mains, tend to disintegrate with nice light effects. Who knew?"

        Works best with glass encapsulated germanium ones. At least that's what "a friend" told me.

        Apparently, a pencil lead from those propelling pencils that use full standard pencil sized leads rather than the short skinny ones, when layed across the terminals of a Scalextric transformer soon start to glow and emit the most horrendous smelling fumes. Again, as told by "a friend".

        1. Anonymous C0ward

          Horrendous fumes from pencil lead? Wouldn't that just be CO2?

          1. John Brown (no body) Silver badge

            "Horrendous fumes from pencil lead? Wouldn't that just be CO2?"

            Depends on what binding agent they used to bind the graphite powder. Clay, or maybe something man made.

        2. This post has been deleted by its author

    9. Pedigree-Pete

      Exploding electrolytics.

      As a new junior tech in a UK radio manufacturers test dept at the end of the production line, I had the job of turning things on for the very 1st time and running through a test document the QA Dept gave us for each product. This one was a portable HF amp, AC powered.

      The end of this box nearest the AC was a BIG (think baked bean can sized) electrolytic, a transformer and another BIG (bean can) electrolytic on the more interesting, almost DC bit of the device (smoothing I think).

      Visual check, red wires going to +ve, black wires going to -ve. Connect up meters at the proscribed test points and turn on.

      Meters rapidly shot to the far right (in some cases so violently the needles came back looking like false eyelashes.

      ENORMOUS bang and a veritable mushroom cloud of paper and green gunk.

      Most of the test bench including me was also covered in green gunk and a nice post apocalyptic shower of shredded foiled paper shards descended.

      Cause. The lower rated bean can that should have been on the DC side was on the AC side of the transformer and vice versa. That box went to the ladies wot fix things once the techs have decided what's faulty. It was still there 3 years later when I left.

      But the incident did create 2 new procedures.

      Check the right components are in the right place, especially large ones that could go bang.

      Don't connect anything to the kit until you're sure somethings not going to go BANG! PP

  7. Anonymous Coward
    Anonymous Coward


    Those acronyms should read Survive, not Support.

  8. Dave Stevenson

    Exploding chips - not fun

    Been there, done that, though fortunately not taking out any other equipment.

    Again as an electronics undergrad, I was building a relay drive circuit using ULN2803 Darlington drivers. Due to a wiring fault one output had been shorted to the supply rail instead of via the relay. When that output was energised the driver exploded, and a small lump of the IC plastic hit me just under the eye! Yes, I counted myself very lucky that it didn't hit about 5mm higher and take out my eye, but it did narrow the fault down to between one or two pins.

    Blowing things up - it's the only way to really learn.

    1. Prst. V.Jeltz Silver badge

      Re: Exploding chips - not fun

      I got a nasty burn of one of the first Athlon processors. That was when I learned:

      "These days processors needs fans and heatsinks and paste at all times and will not even run for 2 seconds without reaching lava like temperatures and a meltdown costing you £80"

      1. Paul Shirley

        Re: Exploding chips - not fun

        Modern silicon does seem a little more fragile than old TTL. Many years ago a miswired quad gate package explosively delidded exposing the chip glowing red. Still worked after cooling down.

        1. Long John Brass

          Re: Exploding chips - not fun

          I had a similar experience with a home brew EPROM burner; The first clue that the circuit I had built was faulty was the silicon under the little window in the package was do a rather good impersonation of an LED.

          The thing that surprised be was the damned thing worked after... Erase, re-program to whole 9 yards.

          Never trusted it enough to use in an actual machine; but kept it around as a scratch EPROM and good luck charm :)

    2. Baldrickk

      Re: Exploding chips - not fun

      I never did it myself, but each of the three desks around me in UG labs managed to separately insert Op-Amps into their circuits round the wrong way.

      They each blew the top half of the casing off and sent it bouncing around the room with a surprisingly large bang.

      I've also seen the magic smoke released numerous times from faulty motherboards (ran a recycling (back into use) shop a while ago) but those occasions somehow all managed to be surprisingly quiet. (small pops followed by fizzles mostly, one "whoosh")

  9. David Gosnell


    I remember a fellow student getting bored waiting for a formal and safety-conscious demonstration of destroying an electrolytic capacitor, and jamming a large one straight into a mains socket in the lab creating quite an impressive (but mercifully harmless) fireworks display. In his defence he thought there was a 50/50 chance of getting it the right way round... 50 had something to do with the reality of course, but is a homophone with hurts.

    1. marky_boi

      Re: Capacitor, HAH !! I raise you 2 stories

      Yeah, I worked as an apprentice for a Telco, we had our own school. This was the 80's. One guy wanted to pay another for a prank earlier in the day. He soldered an electro backwards across the 50V supply in a hidden spot on the cct board we were working on, just as we were being let out for lunch. Every lunch as a precaution the Instructor would turn off the 50v so no fire could start. The cct was duly plugged in as he left. ...... After lunch we all filed in and sat at our desk, the instruction discussed the cct and then turned around and flicked the breakers for the 50v to on. Immediately we were all deafened by a loud bang and confetti. Needless to say pranks were stopped that day...

      Another time another guy was fault finding his project that involved making a set of telephone exchange relays work in a certain sequence, we had built the loom ourselves and were expected to fault find if it didn't work. Fault finding included making each relay work by pressing the relay in the expected sequence and testing the circuit.. All was progressing well until he pressed the second last relay which closed the contacts across 50v. The battery bank that supplied the training site ran a mini mechanical exchange and supplied power to all the buildings and could supply more than 600A without breaking a sweat. For a minuscule fraction of a second it tried to give that 600+A.... results :: one very shocked and slightly blinded student, tripped breakers and vapourized relay contacts and all the magical smoke let out never to be returned..... happy days hope you enjoyed it.... Atomic picture coz that was the Instructor in story #1

      1. SImon Hobson

        Re: Capacitor, HAH !! I raise you 2 stories

        The battery bank that supplied the training site ran a mini mechanical exchange and supplied power to all the buildings and could supply more than 600A without breaking a sweat.

        That may have been it's "rated" capacity, but I bet it could supply considerably more (try adding a zero, or even 2 zeros) than that to a fault.

        I did get told a story (so second hand, and unverifiable) about someone doing work in an exchange and dropping a crowbar across the DC buss bars. Before he could grab it, it turned dull red, bright red, bright orange, and then dripped onto the floor. For good measure, he got a bill from BT for recharging the batteries.

        But given what I know about batteries, and the size of batteries used in large exchanges, the story is at least plausible.

        1. Anonymous Coward
          Anonymous Coward

          Re: Capacitor, HAH !! I raise you 2 stories

          "[...] dropping a crowbar across the DC buss bars"

          The 1960s EELM KDF7 was an industrial process control computer. It had an extremely large NiCD battery for power fail orderly shutdown. The battery terminals were two large studs with hexagon nuts to clamp the connection leads. The terminals were sufficiently close together to bridge them with a spanner. Apparently sufficient current would flow to weld the spanner in place.

          One sat in the yard rusting for while having been salvaged from a fire. On being turned on again it reported the time of its failure.

      2. StargateSg7

        Re: Capacitor, HAH !! I raise you 2 stories

        Can I raise you a 3rd story...DO NOTE: that I am NOT a degreed Electrical Engineer, merely knowledgeable enough to be dangerous! At a special computing facility which shall remain nameless but is located somewhere in Western Canada, we speared a rather large pork roast (40 lbs or 15kg+) onto a smaller-diameter copper alloy buss-bar and attached within the large 100 KV (aka 100 000 volts at probably 400 amps) industrial mains shunt switch circuit (which usually trips ONLY during a lightning strike or transmission line over-current situation!) and then flipped the very large fully manual test switch!

        Let us say that our pork roast was BEAUTIFULLY AND PERFECTLY WELL DONE within 5.0 seconds.

        And yes we DID have a nice bottle of our locally grown wine along with said roast! was NOT the first or last time we did our lunch roasts that way....!!! The key was to SOAK the roast in water first for a few hours with some spices and salt and let the quickly glowing-hot buss-bar superheat said meat within less than 5 seconds until it exploded into a non-conductive container we attached judiciously around the test subject! VERY TASTY i dare say! A Stooopid but DEFINITELY delicious test scenario!

        P.S. The battery and generator backups kicked in during such test scenarios AUTOMATICALLY, so NO DATA or computing system was EVER halted or lost during said lunchtime escapade! We were MERELY running a Emergency Failover and Backup Test Scenario! ;-) :-)

      3. Marshalltown

        Re: Capacitor, HAH !! I raise you 2 stories

        Ah, yes. Those happy days. We ware called in by the office administrator one day because her computer was "misbehaving." We inquired as to the specific bad acting and were informed that something "smelled bad." We could indeed smell hot electric somethings, but had our own, real jobs as well. So we remarked that we hoped her files were backed up, they were. We also told her we were happy to hear that she had not seen any smoke. She made some inquiry to which we informed her that "those ICs run on smoke. If it gets out they stop working." To which she sniffed contemptuously and snarled "no they don't." A very short while later she screamed quite loudly. We went running in to observe, or call emergency services, or laugh depending. She was standing up, backed against a wall. A thin wisp of smoke was drifting out of the louvers on the case. We broke out a screw driver and - after unplugging the beast - dismantled it. There, on the small processor board of a hard drive, in a largish chip was a small crater with a small amount of smoke lifting from it. We showed it to her and said, "see?"

      4. Anonymous Coward
        Anonymous Coward

        Re: Capacitor, HAH !! I raise you 2 stories

        Many years ago, for a high school class project, a friend and I built a railgun. (I'm kinda surprised that teacher didn't get fired...) To supply the high current, we needed a ton of capacitance on the cheap, so we got a couple trash bags of used, disposable cameras from 1-hour film developers, and proceeded to disassemble the cameras and desolder the capacitors - open the case, short the cap, then desolder. I handed a couple to my buddy while "accidentally" hitting the charge button... the screwdriver he was using to short the capacitor ended up with a chip out of the tip...

        Finally, we had 150 electrolytic capacitors, mostly 150 uF each, rated for 300V+. (We checked; didn't want to make THAT mistake!) I had to go home, but he still had some time, so he proceeded to solder them to a pair of rails to make one massive capacitor bank. Then, to test it out, he hooked a bridge rectifier across the rails and plugged it into an extension cord. Apparently he got exactly ONE capacitor wired backwards. He said the bang and 3-foot column of flame was quite impressive.

  10. a well wisher

    Finding fault capacitors with high current PSUs used to be the norm

    Back in the early 80s when repairing old memory boards, at a time when 48 KB was a board about 2 foot square with a gazillion small decoupling caps and one of them was dragging the psu down

    A quick application of a car battery to the 12v line would sort the men from the boys capacitor wise and reduce fault finding time no end

    Note: No I can't remember what chips they were that needed a 12v line either - but certainly remember the process

    1. Missing Semicolon Silver badge

      Re: Finding fault capacitors with high current PSUs used to be the norm


      +/- 5V, 12V.

      1. Solmyr ibn Wali Barad

        Re: Finding fault capacitors with high current PSUs used to be the norm

        "+/-5V, 12V."

        Ah, good old NMOS. Absolutely had to have -5V applied before other voltages or it would fry.

        I managed to fry several NMOS-based 8080 processors. Because of the flaky power supply I had hastily cobbled together. Rather expensive lesson.

    2. Antron Argaiv Silver badge

      Re: Finding fault capacitors with high current PSUs used to be the norm

      A quick application of a car battery to the 12v line would sort the men from the boys capacitor wise and reduce fault finding time no end

      We'd do the same thing, except we used a 5V supply with the current limit turned off, so as not to overvoltage the chips.

      Regarding "Alvin" in the original article:

      He even managed to get the disk working again, by buying an identical drive and marrying its logic board to the platters from the dead machine.

      He should get passing marks, simply for thinking of (and successfully doing) this!

      1. Michael Kean

        Re: Finding fault capacitors with high current PSUs used to be the norm

        Sadly this no longer works since about 40GB drives I think, as they have specific configuration per pair of circuit board and platter pair.

        1. Baldrickk

          Re: Finding fault capacitors with high current PSUs used to be the norm

          I have however done it with an XBox 360 optical disk drive.

          This was to replace the mechanical hardware, the electronics being cryptographically signed and registered to each machine.

        2. l8gravely

          Re: Finding fault capacitors with high current PSUs used to be the norm

          Actually, it worked with Netapps up until around 15 years ago, with the Fibre Channel based drives in the old DEC StorageWorks contrainers on the F330s and F740 series filers. We had a triple disk failure in a raidgroup on a *very* important volume. I managed to pull the working circuit board from the drive making the scraping noises and put it onto the drive which just sat there doing nothing. And presto, the darn thing booted up again and served data again. There were alot of very relieved engineers that day since it held the main ClearCase database for the product the company made.

          That was certainly a stressful day, since going to tape was going to take a *long* time no matter what with DLT7k drives to restore multiple terabytes of data. Ugh!

  11. Fihart

    I always switch off at the wall now.

    Instances from my own computer and friend's of PSU exploding spontaneously when PC off but left plugged in. Visible burn mark on the wall adjacent. PC assemblers using cheap PSUs doubtless to blame.

    Personal best for stupidity; replaced capacitors on a flatscreen. Checked it worked while still in parts. Reassembled. Over-long or over-tightened screws on the VESA bracket at the back, shorted something out. Big bang when next switched on.

    1. John Brown (no body) Silver badge

      Re: I always switch off at the wall now.

      "Over-long or over-tightened screws on the VESA bracket at the back, shorted something out. Big bang when next switched on."

      Or, more likely, screws got mixed up and short ones went in where long ones should go and vice versa. Been there, done that, and now always lay out the screws in the right order/pattern for putting them back in.

  12. Nifty Silver badge

    Can't remember the product details but in the 80s/90s the relays we used in process control switch cabinets had a built-in fuse, one per relay. If it blew, a small cylindrical projectile would fire at high speed from the fuse towards the eyes of the technician standing in front of the relay bank.

    A fuse cover had to be added to each relay.

  13. Prst. V.Jeltz Silver badge

    top tip - If you've changed a capacitor that has blown, especially without really looking at why it blew, When you power the thing up dont get eyeball-to-cap to look for signs of heat , or noise.....

  14. frank ly


    I was once close to a high voltage paper separater capacitor that blew up. The bang and the confetti were impressive. After the bang, the resulting shock/fear reaction, enhances the surreal effect of the confetti in the air.

  15. John Styles

    Many years ago

    A friend, sadly no-longer with us, had a nervous breakdown whilst doing his degree - as part of his rehabilitation he was given some work in the medical sciences research bit of the nearby hospital (some of you may know a city has the mental hospital adjacent to a medical research campus). He was a bright guy but unfortunately had a compulsion to set knobs to zero, which was unhelpful.

    As an attempt to cure him of this a bit of fake equipment was rigged up with a large enticing dial on it [this was in the 70s which explains a lot], set so that when it was zeroed, an enormous capacitor would explode. Apparently he covered the 10 metres to the door in a world record time.

  16. Inventor of the Marmite Laser Silver badge

    One more kaboom

    Does any one remember the onl ISC 3651 desktop colour computer? One of the very first dsktop colour computers, it was an 8080 based machine offering a stunning 127 x 127 charagter based graphics capability.

    It also had a power supply section designed by someone who thought it was a good idea to use el cheapo electrolytice capacitors, and that it would be great to have the rectified mains feed on a track running between the legs of one of those capacitors.

    All went well until the inevitable day said capacitor gave up the ghost and pissed electolyte onto the PCB, straignt between the track and the ground pin of the capacitor.

    Didn't 'arf make a big hole in the PCB.

    1. Anonymous Coward
      Anonymous Coward

      Re: One more kaboom

      Did a Google search - Intecolor terminal???

      Fortunately as a YTS trainee, I wasn't allowed to work on high voltages

  17. Amos1

    Old news. I did that with vacuum tubes in high school.

    In my high school electronics class, early '70's, we were breadboarding five tube AM radios. You know, real voltages and currents, not this wimpy low-voltage stuff. One team had to build in a fault and the other team had to troubleshoot it. My team member and I realized that most of the class was simply "troubleshooting" by looking at the physical layout of the parts and jumper wires on the breadboard.

    So we laid out the parts so the radio worked but with the parts scattered all over the place. For example, the antenna was no longer in the upper left-hand corner and the speaker was no longer in the lower right-hand corner and the Intermediate Frequency amplifier was no longer in the center.

    One of the changes we came up with was to place the tube plate load resistor right next to the cathode bias resistor. If you're never worked on vacuum tube stuff, the plate resistor had roughly 250 volts applied with several milliamps flowing through it. The cathode resistor was the exact opposite. It developed its potential (voltage) by the flow of the current through the tube. So it had very low voltage and its components, particularly the cathode bypass capacitor, was rated at a very low voltage.

    Anyway, the power supply was up on a shelf and we didn't have long leads so the 250 volt plate wire was stretched like a guitar wire to the far end of the breadboard because we had re-arranged the parts layout. (All of the connections were uninsulated alligator clips <- important point).

    While the other team was trying to find the fault by pushing and prodding, they bumped the taut plate power wire. Its alligator clip moved slightly and now also touched the cathode lead of the tube. Not only did this give them a second problem to find, it put 250 volts across the cathode bypass capacitor rated at 6 volts DC. The ammeter on that Heathkit power supply pegged out at 250 milliamps.

    Why didn't the fuse in the power supply blow? Because we were always blowing those fuses through mistakes so we put in oversized ones. Why? Because the instructor yelled at us for using up his fuses, of course.

    Fascinated, we watched that power supply push over a quarter-amp through that poor capacitor but nothing happened. After a few minutes the two of us decided to wander to the other side of the room so we would not be near the breadboard whenever what was going to happen happened.

    A few minutes later, with the two "troubleshooters" hunched over that board and oblivious to the high current, a very, very loud bang occurred followed by non-flaming confetti. The two students fell off their metal stools to the concrete floor but fortunately neither were injured.Smoke filled the lab.

    They and the instructor were very mad at us but since we were far away when it happened, we denied any knowledge. We looked over the breadboard and pointed out the short circuit we already knew about. No proof meant no suspension.

    That capacitor did not shoot anyone's eye out but it easily could have. Lesson learned about wearing safety glasses.

  18. Anonymous Coward
    Anonymous Coward

    Belfast, mid-80s

    Things were mostly calmer then, but not always.

    One afternoon a colleague had just finished some work on a PC, inserting a new card or something, plugged it in, and pressed the mains-on switch. Entirely by coincidence, at that very moment a car bomb left at the end of the street exploded without warning, ours was the closest building not to lose its windows. Took my colleague quite a while to get any colour back in his face...

    1. Anonymous Coward
      Anonymous Coward

      Re: Belfast, mid-80s

      My mother was always very nervous about anything to do with electricity. One day I was fixing our TV. Plugged it into the mains - and there was a loud rumble and a cloud of smoke went up from the area's 132kv electricity distribution yard across the street. My mother was not convinced it was a coincidence.

    2. Anonymous Coward
      Anonymous Coward

      Re: Belfast, mid-80s

      I had a former co-worker who liked to stand behind people doing electrical work, and clap his hands behind their head at the very moment a tool or multimeter lead would touch contacts...

  19. Anonymous Coward
    Anonymous Coward

    uninsulated alligator clips

    on tube (testing) equipment, hilarious!!!!!!!!!!!!

  20. Tim99 Silver badge


    In the 1980s I was in charge of an expensive instrument that had a DAC controlling a large electromagnet. It cycled from a high current to a low current every second or so. The controller had very large MOSFET power transistors switching about 40A Occasionally when the power wobbled the circuit would become unstable and the MOSFETs would explode. The sound was similar to a large calibre revolver report. As that happened every few weeks, until we sorted out the mains supply, that may be one reason why in old age my hearing is crap.

  21. Fedup

    Now this was a big bang!

    Way back in the 70’s I was working in one of the Philips military companies who were involved in the Clansman Radio systems. To filter out all the noise from the tank power infrastructure they suppled a power conditioning unit. This consisted of some of the largest electrolytic capacitors around – they were about 15cm high and about 10cm round. One day the production staff had wire a couple of these the wrong way around. After being turned on in the test area a few minutes later there was an almighty explosion – not a bang, an explosion that shook the whole factory – and it was a large factory. Once the cloud of smoke had cleared everyone started looking for the remains of the test engineer. Just as we got close to the bench, a waving hand with a white handkerchief came up from under the bench - he had just managed to see the capacitors bulging moment before the explosion and dived under the bench. This is a true story.

    1. psychonaut

      Re: Now this was a big bang!

      this is the reg. there will be at least one dick who doesn't believe you....

      writing "this is a true story" will only encourage them...

  22. Anonymous Coward
    Anonymous Coward

    Good shout El Reg. This should be a nice antidote to the occasional "user used CD drive tray as cup holder. Oh how we laughed" entries to On-Call.

    1. Prst. V.Jeltz Silver badge

      hey you stole my anecdote!

  23. Steve Kerr

    A couple of incidents spring to mind

    When in college doing electronic systems I think it was, there was this sorted of breadboarded stuff which was like lego with little diagrams of components on the back - you could plug them in to create a circuit so you had a visual representation from the top. Power was supplied by a separate box with lots of dials.

    Whilst doing an exercise, there was a loud bang, looking round there was a mushroom cloud billowing to the ceiiling and across it whilst a student standing in front had a stricken look of terror on his face.

    From this, we (the rest of his classmates) formualted the theory of random connections in electronis :)

    Another incident when working was in a computer room early 90's and needing a monitor plugged into a headless PC. Designated monitor was on, so we thought, fine. Turned off, unplugged and plugged into headless PC

    <FLASH><BANG!> - I was standing over the top of it when it bliew, the ensuing mushroom cloud billowed up and there was a frantic rush to find anything to dissipate it before it hit the smoke detectors in any kind of concentration!

    That's not including the ICL 2900's that could be crashed by accidently banging into them (never done that) and EPO cable that was incorrectly labelled such that when an elecrician cut it because he thought iwas a power cable that was being removed, the whole DC went down.

    1. David 132 Silver badge

      Re: A couple of incidents spring to mind

      "Like lego with little diagrams of components on the back"

      Not one of these, perchance?

      Gakken EX-150

      I had one myself. Excellent it was.

  24. Andytug

    We had a batch of PC's once with duff auto voltage sensing power supplies...

    Every so often one would set itself to 110 V US instead of the correct 230V UK. They were on desks back to back so some poor soul would be half asleep first thing in the morning when their colleague opposite turned their PC on....then rudely awoken by the loud crack of the PSU blowing a fuse 2 feet in front of them.....

  25. Bernard M. Orwell


    KABOOM : Kit All Broken Out of Malice.

  26. Steve Cooper

    I remember in my days working as a teenager in the 90's in a local PC shop I put a floppy ribbon cable on one pin out (can't remember if it was to the side or just connected to one row of pins) and when I turned that PC on a few of the wires in the ribbon cable lit up like a light bulb.

    A few years before that I remember putting in a random 4mb 72 pin stick of RAM into an IBM PS/2 model 70 and when turning that on the RAM caught fire and a thick, heavy, flow of purple smoke ran across the motherboard, onto the table and nearly made the floor before dispersing. That smelt nice.

  27. My other car is an IAV Stryker

    I'm truly surprised

    ...that no one else mentioned having "Dave Seville"'s voice ring angrily in their head:


    (With apologies to the Bogdasarian family.)

    1. Mark York 3 Silver badge

      Re: I'm truly surprised

      I was going to & still am going with

      Alvin & The ChipSmokes!

  28. Luiz Abdala

    127V or 220V ?

    My sister was working at a University Lab, as an undergraduate, and the place had gone under a major expansion and reform. Repainting, new furniture, more sockets, more lighting... the place was pretty much turned on 24/7 for lab experiments, except for illumination...

    ...but some sensitive lab equipment never survived the first weekend. And then 3 weeks in a row. Computers and more mundane gear as TVs survived without a problem.

    So she asked a lift to complete an experiment on a Saturday, then we would go for lunch, so I waited for her to complete her task, and she explained the whole story. She turned off the lights and hell broke loose. Again.

    We are not sure HOW the sparky managed to do it, but the 127V lights were somehow connected in series with all the power sockets...

    As soon you turned all the lights off, all sockets would switch from 127V to 220V. I noticed literal sparks out of an empty socket when she turned the lights off, which shouldn't happen. At all.

    A multi-meter and some turn-on-turn-off-lights later...

    TVs and computers had multi-voltage PSUs and didn't give a damn about the voltage they were being fed... while the sensitive equipment, being really old, had fixed voltage PSU inputs...

    I've never seen or heard of such a feat.

  29. Mike Dolan

    And the idiot award goes to...

    When I was a lad I used to tinker with very basic electrical/electronic equipment including video recorders (when they used to cost more money in real terms). Friends mum had one that was being skipped as it had broken down, so I got my grubby paws on it.

    Pulled out my trusty Voltmeter and tested power on the AC input side of the transformer. Then tested power on the output side. All ok.

    And then my brain farted and I connected the Voltmeter *ACROSS* the transformer (1 pin on input, 1 pin on output). Despite previously seeing voltage on the output pins, my brain said something akin to "but is the power flowing correctly through the transformer". WTF?

    Amazingly bright flash and a loud bang that left me temporarily deaf for around 5 mins. My glasses caught the main impact of the glass fuse - would have been much worse if I hadn't been wearing those.

    That was the last time I ever worked on electronics. Gave me a very healthy respect for electricity.

    1. DropBear

      Re: And the idiot award goes to...

      Say what...? As recounted, that would have been a non-event - assuming one of the sides is floating, you can't measure anything at all between two sides of a transformer, or indeed produce any kind of current flow, let alone an eventful one. At the very least, a voltmeter capable of measuring mains on the primary side should have had zero problems measuring across the sides of any transformer, regardless of what it was referenced to. I'm sure you did blow up something, but the details seem somewhat misremembered/understood...

      1. Anonymous Coward
        Anonymous Coward

        Re: And the idiot award goes to...

        Unless the voltmeter was set to Amps.....?

        1. Anonymous C0ward

          Re: And the idiot award goes to...

          If it was set to amps, it would already blow up when you measure one side of the transformer.

        2. Solmyr ibn Wali Barad

          Re: And the idiot award goes to...

          Yup, that could be the step missing from description. After checking that voltages were present he wanted to check the current. Set the multimeter to Amps, but...

    2. Anonymous Coward
      Anonymous Coward

      Re: And the idiot award goes to...

      I recently had a similar, though far less violent, incident. I'm working on wiring the garage. There's no breaker panel yet, the whole thing is just run off of an extension cord going to the house (just for now!). With everything nicely lit up from the overhead lights, I was trying to figure out how a line coming from a turned-off switch had 4V-to-ground on it. Hmm. Can't be much current, I wonder if it's "phantom voltage". I switched the multimeter to 10A measurement and put its leads on hot+ground. The building instantly plunged into darkness. I slapped my forehead and went to reset the GFCI in the house.

  30. Gene Cash Silver badge

    TRS-80 Model I

    The original TRS-80 Model I had a reset button on the left rear. Right next to the completely unbuffered expansion port's card edge, which applied inputs pretty much directly to the CPU & DRAM.

    So of course when you went feeling around the back for that pesky reset button, you usually ended up groping the expansion port, and if you had any static buildup whatsoever, you could kill the TRS-80.

    Yup. Did it. Fortunately it was still in the miniscule 90-day warranty.

  31. Version 1.0 Silver badge

    When I was a kid, about 13-14, I got my start in electronics at the local radio club and I can still remember when a guy working on an audio amplifier screwed something up driving a dummy load, the EL34s all started glowing bright blue and we were all standing around looking at them when the power supply went TITSUP and a couple of 300V electrolyte caps turned into steam and confetti - YEH!

  32. Steve Cooper

    Everyone's set their multimeter to measure current and shorted out a circuit, haven't they?

  33. Me19713

    Electronics design with training wheels

    Young EEs are lucky to be toying with low voltages.

    Back in the vacuum tube era, the voltages were much higher. I remember being in middle school, wiring my 65 watt CW transceiver in the bedroom. I learned about paying attention to polarity on electrolytic capacitors one night. Night of the flaming confetti. Dad wasn't impressed.

    1. Anonymous Coward
      Anonymous Coward

      Re: Electronics design with training wheels

      "I learned about paying attention to polarity on electrolytic capacitors one night."

      I forgot to rate the psu capacitor for 1.4 times the transformer's nominal voltage. Measuring the voltage it started rapidly dropping - followed by a bang and confetti sprayed over my bedroom wall.

      When I built my Motorola 6800 evaluation board I didn't realise that tantalum capacitors were polarised. Fortunately I used a "pretty" aesthetic of having them all aligned in the same direction - and got the first one right. I was lucky that the other three that were positioned at right angles also were the right way round.

  34. JeffyPoooh

    "...marrying its logic board to the platters..."

    I've seen that done. (Hi Bob!!)

    It was presumably easier and more successful in those days of Megabyte drives (as opposed to today's Terabyte drives).

  35. Morrie Wyatt

    Large bipolar electrolytic capacitors are always fun.

    Back in the late 70s, I was a young apprentice.

    The company I worked for also imported cheap Taiwanese bench grinders.

    One of these had been returned under warranty, so was on the department manager's bench with the base off to check the wiring. When nothing obvious presented itself the switch was turned on and we retreated to the office doorway. These grinders used a large capacitor and a centrifugal switch to energize the motor start winding with the resulting L/C circuit providing a phase shift to ensure the motor started in the right direction. The grinder started up and seemed to be running normally, until with a loud bang, the capacitor blew its lid, (through the small covered pressure relief hole in the end of the cap) blasting a jet of evil smelling vapor directly at all standing in the doorway.

    We at least now knew what the fault was. The centrifugal switch "didn't", leaving the start winding connected. The start winding and capacitor weren't designed to run for more than about 10 seconds, so the capacitor overheated, boiling the electrolyte until the weak point cried uncle.

    The office became almost uninhabitable for days, and took many months before the smell finally faded to barely perceptible levels.

    I still work for the same company some 40 odd years later.

  36. anothercynic Silver badge


    That's an explosive debut of a new column! That's impressive... taking out pretty much *everything*. Well done!

  37. Andy Taylor

    Just remember

    Always lick your finger before checking the temperature of an IC with it.

    That way, if the IC is getting hot, the boiling of your saliva gives you enough time to remove said finger before it gets burned onto the top of the chip.

    1. Stevie

      Re: Just remember


      *Real* electrical engineers just lick the ICs themselves.

      1. PiltdownMan

        Re: Just remember

        I used to use my upper lip to distinguish slightly overheating ICs. (Very Sensitive)

        Imagine my surprise when I got near the ones that were REALLY hot!?!?!?!?!

        1. Anonymous Coward
          Anonymous Coward

          Re: Just remember

          An old boy in the 1960s was the chief electrical engineer for a large company. He used to test for mains voltage by seeing if he could feel it through the hairs on the back of his finger.

          In those days some radios and TV's were often AC/DC. That had once been essential when some areas still had local 240vdc mains supply. Even after 240vac was standardised it was economic to omit a large transformer in favour of a large resistor to drop a large part of the voltage for the valve filaments.They only had two wires in the mains cable - and sometimes it ended in a two pin mains plug. It was not unusual to feel the AC on the wooden case if line was connected to the chassis.

  38. Stevie


    That's: Total Inability To (with)Stand Unexpected Powersurge I think.

    Nice one.

    1. Anonymous Coward
      Anonymous Coward

      Re: Bah!


  39. IGnatius T Foobar

    Not made by IBM

    As you’d expect of such a student, Alvin “was prototyping a circuit I had put together on a bread board which was connected to a PC clone used by one of my Professors.”

    And I thought by the 1990's we'd already stopped using the phrase "PC clone" ... as if IBM still led the way at that point.

  40. Sideways


    Many many moons ago, when pc's had cluncky on off switches and techs still went out on the piss the previous night, i managed to electrocute myself so well it blew me off the seat.

    A desktop i was assembling had power going to its front switch, the was in the days of 240v not wimpy 3v or whatnot to a soft button. They had little boots on the connectors, now normally i made flipping sure these covered anything "bad" but one day, slightly inebriated from a session the night before one of them was not doing its job properly.

    As i grabbed the sides of the box to move it forward i touched the contact, as it was plugged in at that point there was a bit of a bang, i flew off the stool and all the lights (and everything else) went out.

    I managed to the not only the workshop but the whole buildings breakers, once i managed to get up and stagger about a bit i felt well proud of my accomplishment.

    Not long after one of the boys found out that the CRT screen he was attempting to dissipate was still powered producing a much louder bang and sparks accompanied by another lights out event - again i wonder if the previous nights alcohol might have been a reason for this foopar.

    Nowadays i get a pfy to check things that might produce sparks and bangs, they are easier to replace.

    1. John Brown (no body) Silver badge

      Re: Zzzzappp.

      "a reason for this foopar."

      Did you mean faux pas?

      1. Anonymous Coward
        Anonymous Coward

        Re: Zzzzappp.

        OP could also be reluctant to using FUBAR. This being a family friendly publication...

  41. Kevin McMurtrie Silver badge

    The silencer amp

    In the early 1990s I was playing with MOSFETs in an attempt to build an extremely loud audio amplifier on the cheap. I built 4 Class AB amps on a +/- 45V power supply that could manage 8A momentarily. The circuit design was crude and involved twisted hookup wires between the MOSFETs and the main breadboard. The final build suffered from a bit of distortion and my old oscilloscope showed bits of the waveform missing, which was a typical symptom of intermittent oscillation. I soldered some picofarad caps on the MOSFETs as an easy fix. Now it was weird. Every time I turned on the amp, the MOSFETs hissed, my radio went dead, my CD player spun BACKWARDS, and my oscilloscope went totally blank. I disconnected the oscilloscope probes and it still wouldn't work just being there near the amp. The amplifier felt oddly hot where it shouldn't.

    Moved the oscilloscope and powered on the amp. The scope a drew what looked like spring viewed from an angle, which means that the trace was partially going backwards too. I measured the loops and got 170 MHz on a 'scope rated for 20MHz while its probe was not connected. It turns out that the pins on a TO-220 MOSFET make a fine RF transformer. You're supposed to put series resistors on the pins to stop oscillations; never capacitors. I was energizing all the speaker wires in my room with 170 MHz of high voltage AC. The amp felt strangely warm because it was RF heating my fingers when I touched it.

    I eventually got it working and it was worth every bit of effort.

  42. Paul Hovnanian Silver badge

    Never prototype using your professor's computer.

    That's what teaching assistants are for.

  43. PiltdownMan

    In a (slightly safer) environment...

    When I was a teenager back in the mid 70s, i accidentally blew up a medium sized elctolytic capacitor in my bedroom.

    I had a home made bench PSU capable of supplying upto 25Volts at around 5Amps.

    I accidentally connected the capacitor the wrong way round. It was fun to see the needles on the Voltmeter and Ammeter slowly rising until they both shot up to FSD, then BANG. lots of flying fluff and ears ringing.

    Did that stop me? No. The rest of the bag of about 25 caps, were dangled out of my bedroom window and hanging on Crock Clips. Great fun was had. Wow, the echo around the neighbourhood.

    It did discolour the wall just below my window though.

    Ah, happy days!!

  44. Anonymous Coward
    Anonymous Coward

    In the 1960s I had a bright idea that a pair of SCRs with capacitors could be used as a cross-coupled oscillator in the 12-0-12 volt side of a power transformer. Unfortunately while the theory was probably viable - I guessed at the size of capacitors. Connected to a car battery it failed to oscillate and the insulation on the wires started to smoke and melt.

  45. James_everest

    Tantalum capacitors have polarity

    Before becoming an engineer I worked as an electronics technician bringing up boards on ASIC test systems.

    I had a new board on a riser card. On first powerup, I flipped the switch, I heard this hiss start as it rapidly rose in pitch ... then a loud snap. A puff of smoke then a streak of heat past my eye. The body of the capacity struck the wall behind me and feel to the floor where it sizzled and spun around on the floor for a few seconds. It burned a nice brown circle into the tile.

    I have grabbed 110 volt wires before. But, nothing scared me quite like the viciousness of an exploding tantalum capacitor.

    1. Anonymous Coward
      Anonymous Coward

      Re: Tantalum capacitors have polarity

      Last year I bought some small voltage up-converter modules off ebay - up to about 30v in and up to 35v out. They looked much the same as the buck down-converters I had used in several designs - a small can capacitor at each end and the transformer gubbins in the middle. Voltage adjustment was by a multi-turn pot.

      So - I set one up in the same way as I did the down-converters. Hooked up 12vdc to the input and put a multimeter on the output with no load . Being lazy I didn't connect the meter permanently - assuming I could twiddle the pot and stop to take readings occasionally.

      Quite what went wrong I don't know. While fiddling with the leads to get the meter to show a reading there was a sudden bang and the output capacitor's can shot into the air - ricocheting off my finger. The paper innards were left behind connected to the board. It was fortunate that the can had not hit my face.

      My presumption was that the module was capable of producing more than the stated 35 volt maximum output. Both capacitors were marked as "35v". Looking on ebay I found that other suppliers' apparently identical modules were populated with a "50v" output capacitor. Sent the seller a picture of the damage and pointed out the other sellers' difference - immediate full refund.

  46. Anonymous Coward
    Anonymous Coward

    Did you see me do it?

    "Have you blown things up, broken them, lost data, caused downtime or fat-fingered code in unhelpful ways?"

    Uh, no. So all submissions would REALLY be anonymous, right?

  47. Kev99 Silver badge

    Back in 1981 or so when I was learning RPG, TI-Basic, and COBOL on a TI-990 minis one of our fellow students forgot a semi-colon in a program he wrote. This cause two problems. First, the lack of a colon caused the program to go into an endless loop. Problem two was the code was sending the results to the printer. Unfortunately, the grad assistant was out on lunch. One full super-case of greenbar went thru the printer, which almost fried itself.

    1. Anonymous Coward
      Anonymous Coward

      The ICL2903 was an interesting computer to program at system level. You were programming with microcode to handle its built-in devices.

      One of these devices was a card reader - which had a powerful solenoid that was designed to be activated in short bursts.

      It was reputed that one of the development sequences gained the name "select solenoid, stop, and catch fire". Now when I build anything with a solenoid rated for intermittent use - I always include an independent safety device to cut the current after a set delay.

    2. Stevie

      printer, which almost fried itself.

      A tractor-feed line printer with a duty-cycle not damn near 100%?

      I'd have asked for me money back. Our old 1900 was sending to the printer any time there was enough memory to load XKZE.

      On multi-part paper (which meant crankin' 'ammer force up to 11).

      Up 'ill.

      Buth wez.

      In winta.

  48. John R. Macdonald

    Did I really do that?

    Back in the early 1970's, wandered one slow evening into the main computer room to chew the cud with the operators on duty. I looked for a place to put down the 3 cm thick fanfold printout I was carrying and plopped it onto the top of the IBM mainframe, which had the unfortunate result of making a shaky circuit breaker inside the CPU trip and the mainframe then shut down.

    No real harm done. Open a panel, flip the CB upright, close panel, power on, re-IPL the system and restart the running jobs.

    1. Anonymous Coward
      Anonymous Coward

      Re: Did I really do that?

      Weekend working on our mainframe computer in the 1960s was a "catch-up" exercise to clear any backlog from the week.

      The last job was a long one and finished with lots of real time printing. By mid-afternoon the end was in sight - and the shift leader started to power down the other peripherals. Electrical noise from the papertape reader caused the system to crash. That meant running the whole job again.

      I can't remember how many different unexpected mishaps there were that day on that job. On the final successful run - late in the evening - everyone stayed outside the room until the printing had finished.

  49. Joe Gurman

    How apposite an illustration

    Long, long ago, before the dawn of most things digital for mere mortals, I was an undergraduate at a liberal arts college run Cambridge, Massachussetts that was and remains far too full of itself. Let's call it the Eastern Massachusetts School of Mines. Downriver, there was a more technically oriented university, whose graduates liked to remain among the fleshpots of Boston and Cambridge after graduation, and in the largely pre-digital age what better way to exercise their entrepreneurial muscles than to build and sell high-powered stereo equipment. A freshman roommate purchased a pair of ~ 50 lb. speakers from one (imagine the size of the permanent magnets), and an amplifier from another, a brand-new startup. (I believe the amp had serial number 00001.) One afternoon, as my roommate was enjoying a fine, recreational pharmaceutical and entertaining most of the freshman class through our open windows with his massive (45 W per channel, a big deal in those dark days) system, a transistor in the power supply blew.

    And when I say, "blew," I also mean "blue," which was the color of the perfect, vertical jet of flame, immediately followed by a miniature mushroom cloud exiting one of the vent louvers on the top of the steel enclosure. I didn't know about the persistence of vortices in those days, but I was fairly certain that nuclear fission was not involved.

    Fortunately, the young entrepreneurs were deeply apologetic and gave my roommate a replacement unit (S/N 00007 or so), which survived several more EMSM serenades.

  50. ElectricRook

    You should have seen what has happened when a Schlumberger S9K was brought up after a California Rolling Blackout in 2005. The TIU (Loadboard) couldn't be released because of the design of the interlock. The maintenance manager (contrary to his own SOP) threw the switch. Now the VCC was only like 1.15v even in those days, but the power capability was 5kw which is 5k AMPS! ... well the power supplies had a habit of coming on full power from a dead wakeup, but the relay would have been in the open position only in a safe power down which we didn't have. Max voltage for the SLB HV PS is 12.5v for the SLB digital HV PS. Needless to say when 5kW hits 50 or so under rated caps sparks fly.

    This was another one of those days when I yelled the F-I-R-E word at work ... and meant it.

  51. jimbo60

    Old DEC lore

    This train of thought reminds me of the origins of the phrase "always mount a scratch monkey", one of several great pieces of old DEC lore. for one version of it...

  52. David Shaw

    capacitors exploded? we had an exploding antimatter target

    Im not sure if this is 'entertaining', but it did contain a 'Who, me?' moment. I said 'Yes'

    The excellent University of Sheffield designed us an antimatter production rod, a target for the conversion of incoming pulses of GeV protons, into high energy pbars. The antimatter fell out of the back of the target, in a Pratchetian magic way, as statistically it was able to. I daren't use the word quantum, as most sentences which use the 'Q' word are wrong. We of course also got a lot of electrons, positrons, neutrons and positive and negative pions, kaons and muons, which was lovely, but not wanted in the pbar phase space.

    The pbar target then was basically a solid rod of copper (size of a pencil), using magnetic focussing to self-contain the GeVp to allow maximum matter/energy/matter interaction magic, and a bit of cooling.

    This focussing current was around 320000A pulsed(*), at some hundreds of volts. It worked well, low p/-p efficiency , but we were able to make and store more antimatter than had existed since the big one, quite a while ago. (*other Lithium targets take 1 MA pulses, @ ~6Hz)

    One day, something didn't go very well, I never found out what, maybe a UPS tripped?, the Norsk Data computerised interlock system did manage to dump the incoming 26GeV pulses and switch everything off, but still the room and all the activated engineering inside it burned. Some heroes, as they do, ran towards it & put the 'nuke fire' out.

    I was 'volunteered' into the second response team, as were the other twenty engineers on the un-named project, we were lined up by age - those childless were moved to the lower bias, and then we went in for an annual rad dose in my case I was painting everything with super sticky paint for around 6 minutes to get my dose. Senior colleagues took much more. Our WTF alarms were screaming all the time. We stabilised the errant activated BeO etc dust/soot. Think Wii-U Splatoon, we were the glow-in-the-dark squids.

    Science started again after about a month. I salute Eifionydd who led the team and made the show go on.

  53. bobbear

    Electrolytic bazooka..

    Ah, that brings back memories of the odd high voltage exploding electrolytic PSU capacitor which would bomb out of its case with a large explosion and leave a rail of aluminium and paper as it followed a random trajectory putting life and limb at risk. There's probably a definite potential for weapon development there...

  54. Snobol4


    I remember visiting a PSU factory in the early 80s and looking around their test/rework area. The ceiling was unusually interesting - the usual fibre tiles above the operator’s bench were peppered with hundreds of aluminium cans (from exploding electrolytic capacitors) lodged firmly in them. This was a well-known phenomenon in the early days, which is why modern electrolytics have an "X" pattern formed in the top of the can to allow them to rupture and gases escape without any ballistic effect.

    I can also personally attest to "cratered chip" syndrome. I experienced this when applying power incorrectly to some 74LS TTL logic when I was a teenager. Likewise a black piece of hard epoxy became ballistic in the process and a smouldering and glowing piece of silicon instantly became visible beneath!


  55. Cpt Blue Bear

    Could be a lot worse

    None of my fuck ups involved hydrazine and nuclear weapons

  56. Lotaresco

    A bigger bang for your buck

    Years ago when I worked on avionics we had a shiny new box delivered to the lab which needed to be tested before it was installed on an aircraft. It was bespoke and very expensive and so shiny that it attracted the attention of a project manager. He decided to start it up while we were at lunch and got busy sorting out power and data connections. We arrived back just as he switched on the power. There was a really loud bang and the room filled with magic smoke. The PM ran past us looking like the coyote trying to catch the road runner.

    We were puzzled by the big bang, then someone checked the laboratory PSU. Voltage correctly set to 115V, but oh dear frequency set to 40Hz not 400Hz. Someone didn't understand the use of the decade switch. The manufacturer refused to replace it under warranty.

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