PDA

View Full Version : (Confess) Your stupidest electronics related mistakes.



Martin Hodge
08-19-2011, 05:46 AM
Bet mine tops them all:

Trying to solder with a spool of hookup wire. "Why won't this iron get hot enough?! What's that smell..."

Phil Pilgrim (PhiPi)
08-19-2011, 06:00 AM
One-time stupid: Cutting through live Romex with a pair of sidecutters. Unfortunately there were witnesses, so plausible deniability is moot. Worst of all, aside from the embarrassment, the sidecutters were ruined.

Many-times-stupid: Forgetting to slide on the shrink tubing or connector housing before soldering the connector.

-Phil

Heater.
08-19-2011, 06:02 AM
That tops nothing. I first found myself trying to do that in the late seventies. Along with groping around to pick up the iron whilst carefully watching the joint I'm working on and grabing it by the hot end.
My personal favorite mistake was when I was wondering why a circuit board was glowing red, "I'm sure there are no LEDs on that board" I thought. Turned out to be an EPROM I had plugged in backwards the chip glowing red through the little window.

Beau Schwabe
08-19-2011, 07:25 AM
Leaving a soldering iron 'on' in the garage on the floor, and then going out in the middle of the night barefoot to go grab something and forgetting ... well, being suddenly reminded about the soldering iron....

Then there's the classic ... realizing after you've made all of your solder connections, that you forgot to slide on the heat shrink tubing.

EDIT) I forgot this one.... you read, and it it might explain why I tried to suppress this one ... REALLY REALLY DUMB

Me and a friend of mine got a hold of a microwave oven transformer... we decided to plug it in "free-style" and how fun it was to 'vaporize' random components lying around the workbench. Until I managed to get hold of BOTH ends of the secondary on accident. The next thing I knew, we were both on the floor. My muscle jerk reaction was enough to knock both of us out of our chairs (bar-stool-type) and on our butts. I think I de-fibbed myself in the process.

W9GFO
08-19-2011, 08:31 AM
I was working on the wiring of a three phase motor near the power panel. Breaker was off. I stepped out to retrieve the wire clamps from the conex where the compressor motor was. Only gone for about two minutes. Reached up with both hands to slide the clamps over the wires and, well, somehow the breaker got turned on. On my back with a tingling sensation I remember thinking - that wasn't so bad.

Loopy Byteloose
08-19-2011, 10:23 AM
I'd have to say my stupidest mistake is my most persistent - powering up a device before I am completely sure the construction is right.

It took many years for me to accept the fact that I should first check the circuit board without it being populated by the ICs. Lots of fried components from solder bridges and wiring errors.

There are things I have done that are more embarrassing, but certainly not as stupid.

Humanoido
08-19-2011, 11:30 AM
dropping the most tiny component into the thick carpet... and not having a duplicate on hand...

RDL2004
08-19-2011, 03:19 PM
I sometimes wire things incorrectly. It often causes chips to run a little hot.

max72
08-19-2011, 03:21 PM
I don't count forgetting heat shrink tube.. too recurrent, and I know I'll never learn
Not checking for shorts before switching on a board.
Switch on a board on the table with solder wire below... or bare wires, or forgotten resistors.. or any other conductive junk.
Switching the polarity in a hurry, after having spent time indicating polarity with big coloured polarity indicators.

ctwardell
08-19-2011, 03:36 PM
@Martin, I've done the mistaking hookup wire for solder thing, it was the bare tinned kind, carries heat real fast, burned a nice line across my finger and thumb.

@RDL2004, gee I have a similar breadboard.

@Loopy, testing in phases is probably one of the things we should stress most to those new to electronics. "You CANNOT put the magic smoke back in..."

C.W.

Ron Czapala
08-19-2011, 04:52 PM
One-time stupid: Cutting through live Romex with a pair of sidecutters. Unfortunately there were witnesses, so plausible deniability is moot. Worst of all, aside from the embarrassment, the sidecutters were ruined.

I had a similar experience. I was in my parents attic attempting to run another line from an existing cable. I cut the power off at the circuit breaker box - partially anyway. I did not know that the wire had TWO live circuits on two different breakers! I almost fell thru the ceiling plasterboard and the pliers were welded shut...

Similar to leaving off the heatshrink, I have frequently soldered a phono or headphone plug only to realize that the plug's cap was still laying on the work bench...

Or soldering on a connector before fishing the wire thru the hole in the project box.

bill190
08-19-2011, 04:54 PM
When I was a kid, I connected a 9 volt battery to the secondary of a doorbell transformer and expected 120 volts to come out the other end!

Then not my error, but I found a problem when I was an electronic tech that 1uf capacitors were suddenly being installed on all circuit boards instead of .1uf capacitors. I went to the assembly lines folks and pointed out the error. The supervisor said they ran out of the .1 uf caps, so were using the 1 uf caps instead. She said "They are the same aren't they?"

Pliers
08-19-2011, 04:58 PM
I have made so many mistakes, I do not know where to start. Most expensive, most lethal, most spectacular.

erco
08-19-2011, 05:03 PM
More of a stupid habit than mistake, 'cuz I choose to repeat it. When I'm doing simple 120VAC wiring mods in my house, I rarely turn the power off. I prefer to work carefully, knowing full well that the power is on, working with strippers (insulated wire strippers, not pole dancers, although that would be even better), electrical tape, my trusty Simpson analog multimeter and more wire nuts than I'll ever need. For me, it keeps me honest and just speeds things up.

Haven't been bitten once in 30 years, and I sure hope I didn't just jinx myself. Not recommending this to anyone, BTW.

ZZZZZAAPPP!

bill190
08-19-2011, 05:14 PM
I had a similar experience. I was in my parents attic attempting to run another line from an existing cable. I cut the power off at the circuit breaker box - partially anyway. I did not know that the wire had TWO live circuits on two different breakers! I almost fell thru the ceiling plasterboard and the pliers were welded shut...

That was probably what is called a MWBC or Multi-Wire Branch Circuit. It is two separate 120 volt circuits which share the same white neutral wire. The National Electrical Code now requires the breakers for these circuits to have a tie bar - like with two breakers on a 240 volt circuit. Then you must turn off both breakers.

MWBC...
(See Multiwire branch circuits)
http://ecmweb.com/nec/code-basics/electric_branch_circuits_part/

Ron Czapala
08-19-2011, 05:24 PM
That was probably what is called a MWBC or Multi-Wire Branch Circuit. It is two separate 120 volt circuits which share the same white neutral wire. The National Electrical Code now requires the breakers for these circuits to have a tie bar - like with two breakers on a 240 volt circuit. Then you must turn off both breakers.


That cable was installed by an electrician back in the late 60's to add new circuits for window air conditioners.
The breakers were not adjacent so I figured he was lazy - or just incompetent.
I was in High School and knew that the breakers should have been linked.

Ron Czapala
08-19-2011, 05:30 PM
More of a stupid habit than mistake, 'cuz I choose to repeat it. When I'm doing simple 120VAC wiring mods in my house, I rarely turn the power off. I prefer to work carefully, knowing full well that the power is on...

I do that too but I have been zapped many times and ruined a few screwdrivers...

I used to test for a live circuit by quickly flicking it with my finger (120 only - never 240!!!) O_o

Like you, I am not recommending this for anyone...

I also used to strip spreaker wire with my teeth - don't do that any more

Martin_H
08-19-2011, 05:33 PM
I have recurrent bouts of forgetting the heat shrink tubing, plug caps for phono or RCA jacks, occasional smoked IC's, and leaving my DMM on (once over a vacation).

But the top of the list happened in high school. I was building a nitrogen laser using the plans from Scientific American and it needed a high voltage low current AC power supply. The plans called for a used an old automotive starter coil, and copper clad PC boards for a giant capacitor. I followed the wiring diagram carefully and it worked! I know this because it arced and discharged into my hand which went numb for a minute. Luckily it was powered by batteries so the total power was fairly low.

It scared me so much that I never finished the laser, but I still have the components in my garage. After that experience I've never worked on live AC wiring.

tobdec
08-19-2011, 05:51 PM
My worst is prob back in jvs. We were experimenting with op-amps and I was always the first done with the projects bc for some reason it just came naturaly....well naturaly i got cocky and tried to finish first every time. I was soo rushed that when I got to the final projects...days in advanced...I had to re-breadboard the circuit about 40 times. For the life of me I never got it to work...and everyone eventually caught up to me.

Problem:: I never hooked up the ******* DC!!
Embarisment: I didn't show up for 3 days!

piguy101
08-19-2011, 05:59 PM
In all my time with electronics, I can only remember frying two LEDs unintentionally. But I've let the smoke out of countless components for fun.

bill190
08-19-2011, 06:03 PM
That cable was installed by an electrician back in the late 60's to add new circuits for window air conditioners.
The breakers were not adjacent so I figured he was lazy - or just incompetent.
I was in High School and knew that the breakers should have been linked.

FYI - If it has a "shared white neutral wire", then the breakers need to be on opposite phases - typically next to each other like a 240 volt circuit. Otherwise there is a danger the shared neutral will overheat if it is the same gauge wire as the hots. This works the same as the 3 wires coming into a house all the same gauge. An equal load on both circuits will "cancel" each other out and there will be little or no current flow through the neutral. But if both circuits are on the same phase, then the current flow on the neutral would double and exceed the capacity of the wire (heat).

zoopydogsit
08-19-2011, 07:28 PM
In school I built a PCB for a fully TTL based 2732 EPROM copier as a project, took about a month from proto-type to design, layout, masking, etching, plating, drilling, conductivity testing, soldered in all the components, including a dozen or so TTL chips, etc Nothing made sense when troubleshooting, turned out I'd reversed the mask on the board so everything was backwards! As I was now overdue handing the project in, I then burned a couple of days unsoldering everything and either reversing or resoldering them on the back side. I then ran out of time to troubleshoot it to the point of working.

I now put a line of text on every layer of board I build!

More recently, building another PCB in expresspcb, went to do the proto etch at home, printed it on press'n'peel, etching, drilling, only to find that none of the ICs fit. Turned out that when I printed the image the printer driver subtly resized the image!

I now test layout the most complex compotent to ensure there is no skew and that it all fits.

The following one is not mine, I remember reading in an electronics mag how they'd had an issue with someone building their VHF radio kit (all discrete, requiring hand wound coils, etc). They indicated that the person had perfectly built the unit, but it didn't work no matter what troubleshooting steps they told him to do, first in the magazine feedback column, then in letters and finally on the phone. When they finally saw it in person they found that he'd used perfectly shaped blobs of epoxy glue instead of solder!

localroger
08-19-2011, 08:09 PM
Back in 1996 my company put in four very expensive programmable scale displays as a system. One did the weighing for a three platform truck scale, and the other three functioned as fancy remote displays for the axles. The master transmitted continuous data for the remotes to display on an RS232 bus. The three remote receivers were connected in parallel to the master's transmit pin. These were wired to WAGO spring connectors.

There was also an input for a panel pushbutton switch to tell the scale whether to enable another output driving the outside scoreboard display. We used the same wire, Belden 8723, for this input as for the serial connection. Except the scoreboard control was 110 VAC...

You know what's coming next. Working too fast I wired the scoreboard control in parallel with the serial inputs. It worked fine when I powered it up, unaware that I had converted the scoreboard control switch into a "Push to destroy $10,000 worth of equipment" button.

Oddly enough, the manufacturer honored the warranty.

erco
08-19-2011, 08:23 PM
When I turned on my PC last week, I smelled something burning, and my USB port stopped working. My mistake was leaving my desk chair when 2-year old Amy could climb up, find a metal washer on my desk, and shove it coin-like into the USB slot on the built-in multi-card reader.

I was about to order a replacement unit, but I removed the reader and discovered that one of the traces on the PCB burned off like a fuse. I soldered in a replacement wire bridge and all's well now.

Keep my chair leaned over on the floor, and don't keep change or washers on the desktop!

Tapperman
08-19-2011, 09:14 PM
My Mistake

I built some driver boards for my IGBT's and test each stack (pair) for proper operation and after wiring together all 3 sets I got in a hurry, I loaded my propeller driver and hit the switch to the 24 v bat.

It made some beautiful fire works ... and I'm fairly certain I generated the 4th state of matter ... unfortunately, I wasn't filming (too much of a hurry). So I made a sketch of what came out of the top of the chip.

84261

It visually appeared in a blink of an eye directly over the top of the IGBT and did NOT move (or flicker), it made noise and you could feel the 'heat' on your skin.

I pulled the emergency cut-off switch, and examined the IGBT ... I had went back and re-soldered a gate resister, and in the process (one board only) created a solder bridge, that kept the top IGBT gate 'ON' all the time.

I should know better than to get in a hurry ... 'You only rush to disaster'.

David B
08-19-2011, 09:30 PM
I like using 25 pin "D" connectors for connecting everything to project boards - signal, data, power, sensors.

I had one connector all wired up for some project, complete with 12V power supplied to one of its pins.

The project got its signal from my laptop's parallel port through another 25 pin "D" connector.

I finished up the final wiring, grabbed a "D" connector, plugged it into the laptop printer port, and experienced one of those "Oh sh%^&t, did I just do that" moments. The 12V instantly fried one of the laptop parallel port output bits.

davejames
08-19-2011, 10:58 PM
...why would I want to do this?!?!

I'm trying to improve my reputation!!! :innocent:

agimuhing
08-19-2011, 11:12 PM
Let's see..

hooking up a linear regulator backward, I noticed it wasn't outputting any voltage and got really hot, no major damage though

the usual "forgetting to put the heatshrink on before soldering the wire"

trying to solder with a paperclip instead of solder

Not my mistake: At my school's electronics lab there are a few soldering iron holders that look like this(http://www.gausbach.de/solder.jpg) and some guy put a sponge in the box where the hot iron tip is held. Due to the structure of the holder, the sponge was not seen by the next person who used it. Then, the sponge dried out and caught fire. Surprised the guy using the holder, but nothing really bad happened.

Finally, although not exactly an electrical mistake, I lost control of a pneumatic actuator. I was testing some servo controllers on the actuator when one of them malfunctioned. It made a lot of noise, and I now keep the shutoff valve within arms reach at all times.

prof_braino
08-19-2011, 11:14 PM
Using flux from the hardware store on my first circuit board build. Seems there's some extra acid in plumbing flux that makes the circuit act funny.

Reading all these stories of blunders from experienced engineers makes me want to return to gas light and steam power, or at least stick to software.

bomber
08-19-2011, 11:24 PM
I once was trying to find the 'enable' wire of a computer's swithing power supply, having in mind to use it as a bench top power supply. I was digging around inside of the PSU with THE POWER ON AND CONNECTED and my hand touched the heatsink for the chopper transistor! There was a loud bang, I winded several feet away from where I was sitting before, the lights suddenly turned off, and my right arm was numb. I ended up tripping the GFCI and the power strip! I then decided to just scratch the bench top power supply idea and just use it for parts (like the five otyher PSUs that I got my hands on)!!!!!

W9GFO
08-19-2011, 11:32 PM
I got one. Not long ago I was salvaging some components off a circuit board using my butane powered soldering iron with the blower attachment on. I didn't notice the electrolytic cap,... until it exploded.

ElectricAye
08-20-2011, 12:36 AM
I accidently swapped my heat gun with my mother-in-law's blow dryer.

http://www.best-horror-movies.com/images/return-of-the-living-dead-2-zombie-face.jpg

I wondered why it took so long for my heat shrink tubing to do its thing.

pacman
08-20-2011, 12:41 AM
Man - where do I start?

All the solder/forget to solder/hot end of soldering iron/heat-shrink/wrong side of case from above AND....

The red led that was "somehow" connected to 35V DC that went pop and smacked me in the middle of my forehead (drawing blood).

The $6000 IGBTS we destroyed when commissioning a belt starter [1000VDC] underground (we had the covers off and I was just about to lean forward to actually put them back on when the 6 of them bent BANG! - bits of plastic, and IGBT 'gloop" went every where - lucky for safety glasses).

The 50,000 litres of milk we dumped in a staff car park because in our haste to meet production deadlines we hadn't checked the feedback signals from EVERY valve before the first truck arrived.

The 6 axis - 4 meter reach -robot arm that that had it's control cable severed - and replaced (not by me) that when haywire when turned back on and destroyed just about everything in the room [Mr ABB technician was not on our Christmas card list that year). My mistake was to think that the technician was competent....

The list goes on and on...


(now how can I change my login name....??}

HollyMinkowski
08-20-2011, 01:08 AM
I made a stupid cable wiring mistake and kept plugging these very
expensive switching power supply modules into the cable and ruining
them. I was unpopular for a while.

kiiid
08-20-2011, 02:00 AM
7.30PM: finished soldering 24 seven-segment indicators just to find out they are all upside down on a board that must be ready by tomorrow :)

HollyMinkowski
08-20-2011, 02:08 AM
7.30PM: finished soldering 24 seven-segment indicators just to find out they are all upside down on a board that must be ready by tomorrow :)

OMG
I hope you have a hot air rework station.
It would be hard to use solder wick to remove
all those parts. :-(

xanatos
08-20-2011, 03:31 AM
I must be a complete idiot because I have done almost everything I've read on here, some more than once! :-) I must admit that the most common one is forgetting the heat shrink until after I've soldered everything!

Thanks, you've all made me feel less like the only one who could have possibly actually done some of these things!

Dave

frank freedman
08-20-2011, 04:46 AM
Bet mine tops them all:

Trying to solder with a spool of hookup wire. "Why won't this iron get hot enough?! What's that smell..."

Been there, done that. Did not cut romex, just a three wire bundle carrying 220VAC during a deinstall. Missed one stupid breaker....

When I was teaching the new (at the time) replacement CDC disk drive for an ASW system, I put a bug into the seek circuit which essentially gave 0 feedback to the voice coil drive controller. It would drive the heads to the innermost position at warp speed rather than shutting down. Good problem except that the students would press the reset a few times.... guess seeing is believing. At some point during this lab, the heads stayed in the inner position, and the voice coil retracted to the unload position.. permanently.. :tongue:The senior chief was not amused in the least... Expensive? You betcha..


Frank

P.s. I do not ever forget the heat shrink until after soldering everything, I just happen to remember it after the fact.

Oldbitcollector (Jeff)
08-20-2011, 04:58 AM
Got my nearsighted eyes replaced with distance vision during cataract surgery. Tried to continue to operate by squinting at things for a while. Killed one of my Propeller boards connecting a nice high voltage AC adapter. Resigned myself to getting use to using the tools required to operate with new eyeballs. :)

OBC

Phil Pilgrim (PhiPi)
08-20-2011, 05:56 AM
I think there's a huge market out there if anyone could figure out how to make split shrink tubing that you could put on "after the fact" and which would mend itself along the seam before you shrink it!

-Phil

frank freedman
08-20-2011, 08:48 AM
I think there's a huge market out there if anyone could figure out how to make split shrink tubing that you could put on "after the fact" and which would mend itself along the seam before you shrink it!

-Phil
They do, at least for large items. Sold at Ace hardware, called rescue tape. bout 1" wide, self bonding. nice for cables, hoses, all sorts of stuff. Have not tried it in place of shrink tube though it does have an 8kV rating!!

Frank

Jorge P
08-20-2011, 08:55 AM
When I first started out in electronics (early 90's), I worked at Ken-Ton Electronics for my first electronics job. They had just gotten a run of two prototype Gun-boards for Laser-Tron that had some problems with a feed through. I was tasked with going over the fairly large schematic and finding the feedthrough that was the problem. After about an hour or two I was so aggravated with the over 200 feedthroughs that I took some 30guage wire and filled in all of the feedthrough holes with it. I found out that I ruined 1 of 2 $200,000 prototype boards. Oooops. I think they learned to never have a new employee work on an advanced prototype.

Lets just say I only remained there about a week after that, and to this day the owner won't even talk to me.

Jay B. Harlow
08-21-2011, 05:29 PM
Does attempting to make a pair of electric scissors when I was 4 or 5 count?

I really wanted to play with the electric scissors my older sister's were sewing with, understandably they wouldn't let me.

So I decided to build a pair. I got my safety scissors, a piece of string, and a paper clip, tied them together, and plugged it in.

Promptly sat me on my butt! I walk in the house in a slight daze, my sister asked if I was ok, I say I was and go lay down.

Later I went to collect my invention and remember being pissed that my paper clip burnt thru. I was understandable very appreciative when removing the remains of the paper clip from the outlet.

More recently I smoked a chip and damaged a propeller, both at the same time.

I also melted the headers while attempting to solder the other set of headers on a xbee adapter board...

Jay

kwinn
08-21-2011, 11:05 PM
When I was 4 I saw my grandfather checking the outlets in the house with a pigtail light socket. I decided to do the same so I twisted 2 pieces of wire together and stuck the other ends in the outlet. When I got up off the floor all the lights in the house were out so I went and hid under the bed. I guess that's what sparked my interest in things electrical.

zoopydogsit
08-21-2011, 11:51 PM
Ha My parents were trying to inspire a little engineer and gave me old radios, clocks and tools to play with. Apparently when I was 4 I placed a piece of copper wire between active and neutral, turned it on and ran out to my mum saying " blue flash mummy". What I remember of it was my parents yelling at eachother that night and the dissapointment of not being able to keep the old power switch!

After that there was always plastic plugs in the outlets. I guess that could have easily been my first and last electrical mistake.

OBC's avatar always gives me a smile :-)

bomber
08-22-2011, 12:23 AM
Once, when I was 4 or 5, before I new anything about electrical safety or the dangers of live wiring, I lived by one rule that my parents set very firmly: DON'T PLAY WITH THE ELECTRICITY FROM THE WALL!!!! I once disobeyed that rule, trying to make my own extension cord from a clock radio's power cord. I did not get shocked, but the wires accidentally touched when connected to a night light. There was a bang and a few sparks went flying onto the rug. To this day, there are two black marks on the carpet. Afterwards, my parents took away the power cord and I couldn't use any of my electronics for two weeks.

Loopy Byteloose
08-25-2011, 11:13 AM
This supersedes my previous posting.

Asking for on-line help, but not being prepared with good information.

Spiral_72
08-25-2011, 10:02 PM
I think there's a huge market out there if anyone could figure out how to make split shrink tubing that you could put on "after the fact" and which would mend itself along the seam before you shrink it!

-Phil

Yea, I call it "Hot glue"....

"I am NOT desoldering all that to put on the stupid heat shrink I forgot the first time, screw it! where's my hot glue gun??"

jaeg
08-26-2011, 04:20 PM
Forgetting that the pins are opposite when looking at them from the underside. I wasn't a happy camper when I noticed my mistake.

Edit. Well not forgetting just getting so involved that I didn't notice it.

Martin Hodge
11-26-2011, 09:44 PM
How long would you think it would take a reasonably intelligent adult to realize (from selection, thru ordering, to installation) they've bought 128 Kilobit EEPROMs instead of 128 Kilobyte.


http://www.motifake.com/image/demotivational-poster/1106/deathpalm-fail-facepalm-stick-funny-demotivational-posters-1308795380.jpg

mindrobots
11-26-2011, 11:22 PM
I imagine the actual realization was near instantaneous. DOH!
It's the time and effort you took to cleverly set the trap for yourself that's impressive.

I can only say this because I've done similar things in multiple disciplines! :lol:

Cluso99
11-27-2011, 03:24 AM
1. I was given an old 240Vac indicator light from a washing machine. It had two bare barrels with scre connections. I went to my old valve radio that I was using for parts and took the 2 wire plug and cable from it, with suitably stripped wire ends. I realised I could not hold them and switch on the power point at the same time. So I switched on the power point first, then grabbed the 2 wires to hold onto the light - and to my amazement I ended up on the other side of the room. Tried it for a second time and the same thing happened. At least I then connected the bare wires with a screwdriver before turning on the power and the light glowed red. Nice. Very fortunate I did not tell my parents or they would have banned me from electrics/electronics. I was probably about 6 or 7!

2. After high school I went to college to study electronics. One of the practical lessons involved tuning radios so I brought my newly rebuilt 52MHz valve transceiver to tune the transmitter. We had been told it was the "mills" that "kills". My new power inverter provided 400V DC at 100-200mA. While tuning the plate current, I realised the "Avo8" meter was reversed, so I reached to switch off the power supply with the cable in the other hand. I grazed the metal handle on the front of the transceiver, and voila... my hand clamped severly around the handle - 400V DC 100-200mA from one hand to the other. The only thing to do was to drag it all off the bench and onto the floor. I am still here over 40 years later!

3. My mate decided to teach his wife to solder prototype pcbs for us. He taught her to solder parts using old pcbs and cheap parts. Then he packed all the parts (thru hole back then) and took them home. He explained where the parts went and gave her an example pcb. He forgot to tell her that not all 14 DIP packages were the same. You know the rest... BTW Once she understood the difference she was fine. But she still used to refer to the parts as little yellow pillows, little blue pillows and blue combs.

Martin Hodge
11-27-2011, 03:44 AM
It's the time and effort you took to cleverly set the trap for yourself that's impressive.

"Oh yeah, I need to test out some 128KB EEPROMS... ACK! Digikey's shipping cutoff is in 10 minutes!"
(So in fact, very little effort.)

frank freedman
11-27-2011, 04:29 AM
1. I was given an old 240Vac indicator light from a washing machine. It had two bare barrels with scre connections. I went to my old valve radio that I was using for parts and took the 2 wire plug and cable from it, with suitably stripped wire ends. I realised I could not hold them and switch on the power point at the same time. So I switched on the power point first, then grabbed the 2 wires to hold onto the light - and to my amazement I ended up on the other side of the room. Tried it for a second time and the same thing happened. At least I then connected the bare wires with a screwdriver before turning on the power and the light glowed red. Nice. Very fortunate I did not tell my parents or they would have banned me from electrics/electronics. I was probably about 6 or 7!

2. After high school I went to college to study electronics. One of the practical lessons involved tuning radios so I brought my newly rebuilt 52MHz valve transceiver to tune the transmitter. We had been told it was the "mills" that "kills". My new power inverter provided 400V DC at 100-200mA. While tuning the plate current, I realised the "Avo8" meter was reversed, so I reached to switch off the power supply with the cable in the other hand. I grazed the metal handle on the front of the transceiver, and voila... my hand clamped severly around the handle - 400V DC 100-200mA from one hand to the other. The only thing to do was to drag it all off the bench and onto the floor. I am still here over 40 years later!

3. My mate decided to teach his wife to solder prototype pcbs for us. He taught her to solder parts using old pcbs and cheap parts. Then he packed all the parts (thru hole back then) and took them home. He explained where the parts went and gave her an example pcb. He forgot to tell her that not all 14 DIP packages were the same. You know the rest... BTW Once she understood the difference she was fine. But she still used to refer to the parts as little yellow pillows, little blue pillows and blue combs.

O M G a two time Darwin award looser!!!! Don't bother with any lottery or other things of chance, I do believe you are seriously overdrawn on your account at the Bank of Good Luck!!!

Frank

ajward
11-27-2011, 05:23 AM
Not my most destructive, but way up on the clueless scale... always forgetting one of the most important lessons of electronics: A cold soldering iron looks exactly like a hot soldering iron! :-|

electromanj
11-27-2011, 05:37 AM
Well where should I start....

My fondest mistake would have to be my first attempt at a dc motor controller that I (incorrectly) modeled from one of the engineer's mini notebooks. After witnessing the flame and whistling noise shoot out of the top of the SCR like a mini jet engine on the breadboard I sat back, got ahold of my thoughts and erupted with enthusiasm!!!!!! Been hooked ever since.

My least favorite has to be letting myself be rushed by an impatient customer while adjusting a static phase converter. One time forgetting to turn off the disconnect and wammo! 480 to ground. If I would have grabbed two phases I probably would not be telling this story right now. (Nobody has ever rushed me since that day.)

This one was my own stupid. Did not allow enough time for a 300 hp VFD's capacitors to discharge before putting a ratchet on the input lugs to disconnect the wires. Not as bad as it sounds but still, that was dumb.

As far as the heatshrink goes, when underground cable is cut it usally requires a short piece of cable to make up the distance between the cut wire. That amounts to two crimps and two heatshrink insulations per cable splice. I'm not going to go into detail here, but rest assured after you make your first double connection with 500 MCM and forget the heatshrink, you remember it from then on.

I could continue, but I think I done enough self defamation for one night.....

traVis

bsnut
11-27-2011, 10:35 AM
Where do I start, my hobby in electronics or my job as an electrician. I start with my job as an electrician.

I was working on a job site and was wiring up single pole switches and installed them upside-down "no - ffo" when it should've been right-side up "on - off". I didn't do one, I did 10 of them until the job foreman said something and I was the lead electrician on this site. Even the leads make mistakes.

Don't try wiring up a 120vac ballast on a 277vac it doesn't work and made this mistake as well.

Now my hobby. I was hooking a RC-4 SCR board that I bought from Parallax (when they were selling them and sold by EFX-TEK now) and plugged the servo cable the worng way and end up putting 5vdc on the serial I/O line. Of, course the magic blue smoke came out to say hi.

I also made the heat shrink mistake as well when making cables and found that electrical tape saves me everytime.

One thing, I can say is that once you make one mistake for one thing, you don't normally make them again and you learn from it.

idbruce
11-27-2011, 11:20 AM
This pertains to electrical instead of "electronics". I have two of them.

In my early days, while performing electrical work on a new residence, the heating and air guys were in the basement banging on their tin and driving me bonkers. However, I got even when I decided to push a metal fish tape towards the panel. Upon arriving at the panel, the metal fish tape hit the buss bar and let out a "BIG BANG". Scared the bejeezers out of those tin guys and put a nice melt mark on the buss :)

On another job, I was working inside of 100 amp main lug sub panel, which had a 100 amp breaker inside the sub to shut off power to the buss. The 100 amp breaker had to be relocated to a different position within the panel. I had this breaker shut off while performing other work within the panel. When it came time to move the breaker, I simply removed the wires from the lugs, forgetting that they were still actually hot. While moving stuff around, one of the live wires grounded to the cabinet and we had our second "BIG BANG".

Inquisitive minds need to know... I was just testing my own theory of relativity :)

ratronic
11-27-2011, 05:13 PM
When I was about nine years old, I was fascinated with receiving out of town A.M. radio stations at night. So I took my 120 volt tube type radio apart and attempted to provide a better ground and antenna as I heard that would improve reception.
I'm not sure what I did but at one point I blew the main circuit breaker for the house (lot's of sparks). My dad was so mad because he had run outside to try to catch the kids who had previously been playing pranks by flipping our circuit breaker and running.

Microcontrolled
11-27-2011, 05:40 PM
3. My mate decided to teach his wife to solder prototype pcbs for us. He taught her to solder parts using old pcbs and cheap parts. Then he packed all the parts (thru hole back then) and took them home. He explained where the parts went and gave her an example pcb. He forgot to tell her that not all 14 DIP packages were the same. You know the rest... BTW Once she understood the difference she was fine. But she still used to refer to the parts as little yellow pillows, little blue pillows and blue combs.

Your friend had a wife who would solder PCBs for him?!?! AND your PCBs as well?!? Lucky man!

Prophead100
11-27-2011, 11:03 PM
Hmm... My biggest mistake was leaving a couple un-fused low voltage connectors uncapped at the other end of the boat with my 6 year old son nearby. He promptly helped by connecting the pigtails in reverse resulting in two shorting circuits and instant billows of smoke from one end of the boat to the other. The last words I hear before the smoke were "Here Dad, you left these unplugged"

Cluso99
11-28-2011, 01:06 AM
There is certainly something to be said about learning by experience ;) However, learning by others experience is far safer!

lanternfish
11-28-2011, 04:06 AM
Like many of us older forumistas I have experienced a variety of "Doh!" moments. The funniest was when I was in a band quite a few years back. During the evening one of our guitarists, for some unknown reason, walked around the back of a speaker cabinet, tripped on the cable and ripped it out leaving the jack in the socket. I stopped playing and went over grabbed cable, put one leg between my teeth to strip back insulation ..... fixed it in the end!