Dumbest 'electronic' mistake you ever made

[Calchaqui]

Sadly I've made a lot....today i did the longest one, just received a pack of 10 brand new little 12v linear-transformer psu for alarms, then i measure polarity with my tester in voltage and i did get (- center,) in the 10 psu... i said weird stuff :S, i did a second measurement by doubts, and i began to open that damn plastic case with no screws just glued. Desolder wires- switch em and solder back again, re-glue the case and go for the next one and the next one when while soldering the third i watch my tester and see the fuck** red tip in the COM port it was my nephew . This was even more painful than that day when the solder iron fallen in my leg and i threw all the bech and break in a half a very expensive radeon 9800 ang got a tiny hole in my leg

[Calchaqui]

Re: Dumbest 'electronic' mistake you ever made

I just remember a funny one, in 1994 was doing my first Computer repair workshop, computers over here were an UNKOWN MISTERY and the teacher was disarming a 486 dx4 machine when a kid ask him if it was good to plug a pci/isa board in the mobo off ,but pluged in..., the Teacher said OFF COURSE you can do that!, i could see the mobo green led on and the Teacher with a very large board (probably an Hercules VGA/LPT1) when the board was about 1 inch from the port: a very large lighting spark made an arch and the old teacher began to scream with static hair and the whole port turn black, evreyobody was scare!!,they said computers can kill because they use 1000000volts !

[RJARRRPCGP]

Re: Dumbest 'electronic' mistake you ever made

Static from the carpet won't make stuff black, lol.

Sounds like a shorted 12 V rail to case.

[SteveNielsen]

Re: Dumbest 'electronic' mistake you ever made

I've got a very long list. The dumbest would have to be involving high voltages.

[goontron]

Re: Dumbest 'electronic' mistake you ever made

worst one was watching a tube radio burn down when the filter cap let go. first the filter cap turned into an arc welder, then the ($200) power transformer went up in flames.
thats also why i won't use a solid state rectifier in place of a tube rectifier. if it was the 5U4 that belonged there, it would have failed and saved the tranny.

[stj]

Re: Dumbest 'electronic' mistake you ever made

or you could fit a fuse - just saying.

[Topcat]

Re: Dumbest 'electronic' mistake you ever made

I've gotten a hold of a few live flybacks before....that will wake you up for sure...

[goontron]

Re: Dumbest 'electronic' mistake you ever made

or you could fit a fuse - just saying.

with a non-polarised cord, no.

[stj]

Re: Dumbest 'electronic' mistake you ever made

with a non-polarised cord, no.

why? it's just to protect from overcurrent.

[goontron]

Re: Dumbest 'electronic' mistake you ever made

why? it's just to protect from overcurrent.

one blade of the cord goes to the chassis on non transformer sets, if the fuse blows the chassis goes live. obviously thats not the case on units that have trannys, but its 100% discouraged.

[stj]

Re: Dumbest 'electronic' mistake you ever made

i didnt mean fuse the device, i meant inline with the rectifier incase it shorts.

[kaboom]

Re: Dumbest 'electronic' mistake you ever made

one blade of the cord goes to the chassis on non transformer sets, if the fuse blows the chassis goes live. obviously thats not the case on units that have trannys, but its 100% discouraged.

Then wire it correctly, and let the fuse do its job.

"It's only original once" has its limits when it comes to safety- do we still wire houses like we did in 1895?

FWIW, a blown rectifier does not always save the power TX; as far as I'm concerned, it'll kill it- like when the filaments of that 5U4 melt and hit the plates...

https://www.youtube.com/watch?v=jUzYM-XxpRI

[Calchaqui]

Re: Dumbest 'electronic' mistake you ever made

I've got a very long list. The dumbest would have to be involving high voltages.

I bet you tell us at last one!. I'm pretty sure High Voltage is a plus+ for mistakes, and the most hazardous ones .
A colleague of mine got ruined his whole triceps muscle when fixing a microwave oven, a tiny tip of the wire pierce the high voltage transformer insulation and stick in his elbow till a siemens breaker saved his life but got permanently numb the triceps. I've read in local newspapers of amateur repair people who was found dead in bed from a heart attack after receive a discharge trying to fix their microwave oven, meaning it has a killing delayed effect.

[Calchaqui]

Re: Dumbest 'electronic' mistake you ever made

Static from the carpet won't make stuff black, lol.

Sounds like a shorted 12 V rail to case.

I was too young to understand details at that time, but Im pretty sure he shorted 3.3v and 5v rails to case, the funniest was his hair stand up and he threw the large Hercules board with fury against a wall and began to scream like a mad monkey. Evrething got burnt, even the psu and the computer repair workshop got discontinued in the absence of a computer!!, at that time, over here, a computer costs 5 month salary. Sorry for my english.

[stj]

Re: Dumbest 'electronic' mistake you ever made

I bet you tell us at last one!. I'm pretty sure High Voltage is a plus+ for mistakes, and the most hazardous ones .
A colleague of mine got ruined his whole triceps muscle when fixing a microwave oven, a tiny tip of the wire pierce the high voltage transformer insulation and stick in his elbow till a siemens breaker saved his life but got permanently numb the triceps. I've read in local newspapers of amateur repair people who was found dead in bed from a heart attack after receive a discharge trying to fix their microwave oven, meaning it has a killing delayed effect.

high-voltage is fun,
high-current is the danger.

there are video's - probably on utube of people dropping spanners and buss-bars across a 12v car battery.
800+ Amps makes for one hell of a makeshift bomb!!!

[Calchaqui]

Re: Dumbest 'electronic' mistake you ever made

high-voltage is fun,
high-current is the danger.

there are video's - probably on utube of people dropping spanners and buss-bars across a 12v car battery.
800+ Amps makes for one hell of a makeshift bomb!!!

Yes, Joule effect kills you in a bad way , high voltage-low current gives you a heart attack . Those are my ideas, dunno for sure.

[delaware74b]

Re: Dumbest 'electronic' mistake you ever made

Not so many 'electronic' mistakes unless you count some of my more famous electrical mistakes such as:

Cutting through a conduit that had no AC in it - it was only for the fire alarm in a state police barracks. 10,000 angry crickets in my ears after shutting off my reciprocating saw. Didn't get in trouble, they were pretty cool with it.

Troubleshooting a 15 year old message board. Pulled out 2 8x7 pixel elements and it went stupid. I had 2 470uF 35V Panny caps grenade in my face. They retired the sign and it stayed that way for about 6 years until the pylon sign was replaced with a regular sign.

Separated a neutral splice in a house. It turns out it was a shared neutral and put 240 volts through 10 cfl's, they ran real bright for about 30 seconds and started releasing all the magical smoke.

Tripped a 480-volt ground fault protection breaker that took out 1/3 of a school. I did that one by adjusting a 277-volt switch in a box to put a plate on it. Turns out a wire was damaged going to the switch and got pinched. That fault tripped 3 breakers in 2 different panels.

More things similar to that have happened......

[kaboom]

Re: Dumbest 'electronic' mistake you ever made

Separated a neutral splice in a house. It turns out it was a shared neutral and put 240 volts through 10 cfl's, they ran real bright for about 30 seconds and started releasing all the magical smoke.

That could've gone worse, as you know. At least it was just cheep (compared to electronics) CFLs. ASSuming you didn't fry any electronics...

Tripped a 480-volt ground fault protection breaker that took out 1/3 of a school. I did that one by adjusting a 277-volt switch in a box to put a plate on it. Turns out a wire was damaged going to the switch and got pinched. That fault tripped 3 breakers in 2 different panels.

More things similar to that have happened......

Shh... you can't put the smoke back in once you've released it. I tried- needed a 9V regulated power supply to test something, so whipped one up with a "zener boosted" 7805. Only I put a 6.3V nichicon HM on the 14V input.

Hmm... idle current seems a bit high- Hsssssss! Wow! That smells like ammonia!

[ben7]

Re: Dumbest 'electronic' mistake you ever made

Shh... you can't put the smoke back in once you've released it. I tried- needed a 9V regulated power supply to test something, so whipped one up with a "zener boosted" 7805. Only I put a 6.3V nichicon HM on the 14V input.

Hmm... idle current seems a bit high- Hsssssss! Wow! That smells like ammonia!

I had a similar experience. I was at my computer looking something up for some sort for circuit, and I had the breadboard with me. After I was done, I moved to my workbench ...
Well, it turns out, that the bulky capacitor on there popped out (darn crappy breadboards). I had just pushed it back down onto the breadboard. Well it ended up being connected backwards. Powering on the circuit, all of a sudden I noticed a faint bubbling sound, and the power LED dimmed ... I caught it just in time, that cap almost popped. It was a vented cap though, so it would have just made a puff of steam, but still! ... it SCARED the hell outta me ... now I double check capacitor polarities, lol.

Separated a neutral splice in a house. It turns out it was a shared neutral and put 240 volts through 10 cfl's, they ran real bright for about 30 seconds and started releasing all the magical smoke.

Hahaha

I've got a very long list. The dumbest would have to be involving high voltages.

Hahah, same. Like the first time I took apart a camera flash unit. Yep, got quite a surprise out of that one.

or you could fit a fuse - just saying.

LOL ... or pull the plug, or turn off the power switch (if there is one) xD

[goodpsusearch]

Re: Dumbest 'electronic' mistake you ever made

I was playing with a cheap psu once and I removed its HEC primary caps that had real capacity 423uF to replace them with Teapo LXK 200V 470uF with a real capacity of 490uF.

I plugged the psu to AC, turned it on and everything was ok at first but then started a boiling sound! 1 of the primary caps I had connected backwards!! I was lucky to stop it before the cap exploded. When I touched it after AC disconnection it was hot enough to burn my finger.

Oddly, the cap survived! It didn't vent and its ratings (esr, uF) didn't change. The cap got lucky!

It's the cap on the left.