Dumbest 'electronic' mistake you ever made

[Spork Schivago]

Re: Dumbest 'electronic' mistake you ever made

Note also that electrolytic caps, before the electrolyte gets damaged by reverse current, it will still work like a capacitor though at lower capacitance. There are also nonpolarized aluminum electrolytics that are designed a bit different and can take charge in either direction.

There are solid electrolyte electrolytic caps as well as tantalum electrolytic capacitors that are dry.

Just the run-of-the-mill aluminum electrolytics with rubberized bungs are "wet".

Thank you. So why are electrolytic caps polarized? I know you said some aren't. But the ones that are. My understanding was there where two plates inside the caps with a dielectric between them. One plate builds up positive charges, one builds up negative charges and when the charge is equal to that of the battery (or there about) the charges stop building up and the current stops flowing. When the battery is removed, the cap "discharges". With just two plates, why does the polarity matter? Are they made out of different materials or something?

[Heihachi_73]

Re: Dumbest 'electronic' mistake you ever made

There isn't stuff in the power supplies to prevent them from going up in smokes when you flip that switch? I guess I'm lucky here, when we flip them to 220V, they just don't work. I just figured if you're in a country where 220V is the standard and you flip it to 110V, the power supply would detect the much higher voltage and just somehow prevent it from going through or knock it down to 110V somehow.

Not with old power supplies. We do the same thing with old AT/ATX PSUs which aren't worth recapping. If your mains is 110V (or 100V in Japan), running it switched to 220-250V probably isn't going to do much, if it powers on at all, but running a 110V system on 230V will let out the magic smoke pretty quickly.

Likewise running it hooked up to a MOT.

[Spork Schivago]

Re: Dumbest 'electronic' mistake you ever made

Not with old power supplies. We do the same thing with old AT/ATX PSUs which aren't worth recapping. If your mains is 110V (or 100V in Japan), running it switched to 220-250V probably isn't going to do much, if it powers on at all, but running a 110V system on 230V will let out the magic smoke pretty quickly.

Likewise running it hooked up to a MOT.

I'd love to see a video of one of the older ones switched to 110V but hooked up to a 220V. Here, I sometimes get customers who bring in a PC and said it just stopped working one day. Every now and then, I'll find the PSU switched to 220V. They just don't power on at all. 9 out of 10 times, they have a child who flipped it. In high school, we used to hang out in the computer lab. We setup a Linux server to replace their very old and outdated Novel Server. The IT department found out and was okay with it. That was great.

When we got to 11th or 12th grade though, we realized if we took the terminator off the BNC cable, the computer teacher would call us out of class to have us fix it! If we were having a bad day or something, one of us would take it off and one of us would get a call. We'd come, mess around for a bit and say something like omg, this is worse than I realized. I'm going to need help. Any way you can get <blah> out of class as well? Sometimes, we'd switch it up a bit and instead of removing the terminator, we'd switch a couple PSUs to 220V. Almost always, no matter what class we were in, the teacher would allow us to leave. Next thing we knew, teachers were having us fix their PCs! The IT people where a company called BOCES and they were in charge of something like 5 or 6 school districts. It'd take them quite a while to get there to fix a PC so the teachers would just start calling us. Eventually, they even started bringing in their home computers for us to work on. Brings back good memories!

In the other computer lab, we setup a Linux box, with the teacher's permission, and did a dual boot. We'd stay after school and have these get togethers that we called LAN parties. We'd have Linux on a boot / root disk and we'd boot off the discs to play old school NES games or we'd go into DOS and play a game called Descent. One day, I'm sitting in the lab and BOCES shows up. They asked the teacher who sat at PC <blah> She said me. They came to my PC and asked if I could move over for a bit. I said sure. The restarted the PC, Linux popped up and they asked if I knew anything about it. I said I did and that we installed it on there. They said we had to remove it because it was becoming the primary domain server on their network. We said we could change that but they said no. The teacher said she gave us permission but they insisted and thought it was some sort of security risk. They let us keep the Linux server in the other room because it was off the main network and connected to something I think that was called a Token Ring network. It was a long time ago.

We also found a way to get the codes for the school phones! We could dial out or get on the PA system! On the very last day of school, when we were never going back, when we was getting ready for college and everything, we setup a tape recorder to dial the PA code and we played Alice Cooper's School's Out! It was great. The teachers came looking for us but we anticipated this and had someone else, not in the computer club do it.

Some kid, earlier in the year, found out we knew the code and blabbed his mouth. It got back to the principal and he called me into his office. Gave me some speech how they had to pay big bucks to get someone to come in and change the code. I told if he wanted, I could change it for him! He didn't find that very funny and asked for one of my friends name. I gave him one. He pulled up a program called SView and typed in the kids name. It showed his whole schedule, his emergency information, his grades, everything. The principal said something like, "See? I have power too!". What he didn't realize was we not only had SView and all the databases for every school in our district, we also had every locker combination for every school! Each locker had 5 combinations and every year, they'd cycle through them. So how they were able to reprogram the combinations.

Only once I changed a person's grade by editing the database. A kid came to me and said he knew I was real good at PCs and heard some rumor that I had access to the grades. He said he'd pay me 20$ if I could get it so he could pass this subject. He said because of how old he was, if he didn't pass this year, he wouldn't be able to graduate. They kick you out at 21 I guess. He said he didn't want an A or anything, just a passing grade. I told him I didn't know what he was talking about but I ended up giving him a C. After he got the grade, he came back and tried giving me money but I just said I didn't have anything to do with it. As far as I know, they never found out.

[Dan81]

Re: Dumbest 'electronic' mistake you ever made

Okay...so if there's one DUMB (and it's really the dumbest thing of the century...),it was trying to power up a wet Deer PSU. You can imagine what happened afterwards. Oh well,at least nothing of value was lost.

Small hint:It starts with F and ends with s,and it has 9 letters including F and s.

[TechGeek]

Re: Dumbest 'electronic' mistake you ever made

Second worst thing of the century:
Kicking a computer. Lost an Western Digital Caviar Blue 160GB IDE HDD.

[shovenose]

Re: Dumbest 'electronic' mistake you ever made

Second worst thing of the century:
Kicking a computer. Lost an Western Digital Caviar Blue 160GB IDE HDD.

Eh, not a big loss... today flash drives are bigger.

[TechGeek]

Re: Dumbest 'electronic' mistake you ever made

It had my Windows 7 account on it. Whoops. BIG whoops.

[eccerr0r]

Re: Dumbest 'electronic' mistake you ever made

ARRRGH. Stupid mistake! I had that camcorder I was working on connected to a bench power supply... hooked it up BACKWARDS. I smell "magic smoke"...


Oh well... Now it may really be a lost cause...

[ChaosLegionnaire]

Re: Dumbest 'electronic' mistake you ever made

today's bug of the day and dumb mistake i made: overtightening of heatsink screws causes undetectable radeon 9600xt video card and causes the mobo to play dead. thought the video card kicked the bucket...

tried one last reseat of the ati silencer 1 heatsink and did not overtighten the screws excessively this time and hey presto! card boots again. hope that didnt cause any damage to the bga that might shorten the lifespan and spoil the video card again sometime down the road.

[SM-Piyes90]

Re: Dumbest 'electronic' mistake you ever made

I remember been repairing a pcb , after i finished i let a tiny drop of saliva on it , i just left like that thinking it will just dr ( no big deal ).

Just after powering it up , everything worked well , the repair was good .

After that the cliend returned it , and guess what , Whole set of IGBTs was gone .

[TechGeek]

Re: Dumbest 'electronic' mistake you ever made

Whoops. BIG whoops.

[Dannyx]

Re: Dumbest 'electronic' mistake you ever made

Not sure if it's really a mistake or not, but it's still pretty funny: I was working on a GPS which would no longer turn on. It was a pretty fancy unit, with a built-in flash card reader and actually ran Windows off of this card ! So anyway, I was tracing the power lines to see where power is supposed to go and after I found what I thought was a faulty component (I think a regulator or transistor) I applied 12v straight from the wall adapter after the said component thinking it would power the thing on...big surprise, a puff of smoke came out from somewhere on the board I was like "ok, there's no way I'm fixing this thing now since it's all SMDs anyway - put it all back together and throw it in the trash". I did so and out of "due-diligence" I plugged it in again and...the GPS turns on...WTF ? I then figured out that all I did was remove the "hard drive" (the flash reader) since it was on a socket and plug it back in and that got it going (with a little help from that jolt of power which fortunately wasn't enough to fry any chips)....go figure

[Cableaddict]

Re: Dumbest 'electronic' mistake you ever made

My dumbest mistake is probably the prize-winner:


I once rebuilt a mid-level recording console, with lots of custom circuitry, and a completely new, discrete summing amp section.

As I wanted my hard work to last for years, and not corrode, I washed all solder joints with Cramolin red, let it dry, then sprayed over them with a phenolic plastic spray (specifically designed for such things.

What I didn't know at the time was that Cramolin red is electrically conductive. ( ! ) - And it has a tendency to saturate the insides of phenolic circuit boards. (Who knew?) The circuit boards acted like sponges, and the plastic spray kept the Cramolin from fully evaporating.

Combine that with my have boosted the rails voltage in the console, and...

One day I came to work, and the entire studio was full of black smoke. The console had caught fire. Something like $200,000 in damages.

True story.


Do I win?

[joshnz]

Re: Dumbest 'electronic' mistake you ever made

My dumbest mistake is probably the prize-winner:


I once rebuilt a mid-level recording console, with lots of custom circuitry, and a completely new, discrete summing amp section.

As I wanted my hard work to last for years, and not corrode, I washed all solder joints with Cramolin red, let it dry, then sprayed over them with a phenolic plastic spray (specifically designed for such things.

What I didn't know at the time was that Cramolin red is electrically conductive. ( ! ) - And it has a tendency to saturate the insides of phenolic circuit boards. (Who knew?) The circuit boards acted like sponges, and the plastic spray kept the Cramolin from fully evaporating.

Combine that with my have boosted the rails voltage in the console, and...

One day I came to work, and the entire studio was full of black smoke. The console had caught fire. Something like $200,000 in damages.

True story.


Do I win?

That's quite a impressive mistake.

[TechGeek]

Re: Dumbest 'electronic' mistake you ever made

You win. Close the thread.

[ChaosLegionnaire]

Re: Dumbest 'electronic' mistake you ever made

more dumb electronic mistakes made by me:

first one, i didnt put the power button header on the right jumper pins on the mobo. so i thought the mobo was bricked from some kind of esd and wont power on. had to use a jumper wire to short the green wire on the atx connector to turn on the psu and board. realised the mistake a few days later. lesson learnt: dont tinker with electronics in the morning while sleep deprived.

second one, computer kept suddenly randomly rebooting after 30 mins to 1 hour from a cold boot. thought it was a psu issue. swapped psu and still the same. then another system with that psu i thought was faulty also did the same. swapped another psu again but still the same. swapped ram and still the same.

so i stuck in a post card to see what was wrong with the system and i saw on the post card, the reset button led was lit and flickered as i moved the reset button around. stuck/faulty/partly shorted reset button was the cause. pulled out reset button and system worked fine thereafter. phew!

[Agent24]

Re: Dumbest 'electronic' mistake you ever made

I'm amazed at how many times I've seen a faulty button cause problems in equipment. I always regarded switches as one of those components which 'never fail' - and yet, now, my experience tells me that switches (especially tactile buttons) seem to have a failure rate which matches that of any average component.

One failure I have yet to experience is a faulty transformer. (Though I've seen an inductor cooked due to a shorted transistor)

[Curious.George]

Re: Dumbest 'electronic' mistake you ever made

Dumbest mistake I've seen someone ELSE make:

~17" x 70" wirewrap panels (Augat) used in a piece of custom test equipment (i.e., where the serial number is never more than one digit!) DIP technology (40 years ago). So literally thousands of DIPs covering the surface of the panels. Gobs of decoupling capacitors on the three power supplies feeding each panel. Backside a ratsnest of #30AWG Kynar.

Folks who built the panel used the wrong caps -- too low of a voltage rating. So, apply power and blow every cap on the board (400A power supplies). Of course, you can't unsolder the caps with all that wire in place...

(someone lost a shitload of money on that deal!)

[RJARRRPCGP]

Re: Dumbest 'electronic' mistake you ever made

Something like $200,000 in damages.

Was that due to the building being engulfed in a fire. Or was that equipment like you would expect at a Michael Jackson facility???

[eccerr0r]

Re: Dumbest 'electronic' mistake you ever made

Stupid thing I did last night: Scoping high voltage on your lap.

Last night just about ready for bed I was curious about a 325W power inverter. I had it on my lap and I didn't have pants on, assuming that the inverter should be isolated I should be fine...

well... no.

Turns out that I had one pole of the high voltage hooked up to earth ground (because the 'scope grounds one input) and the 12VDC ground was floating-and touching my skin. When I touched earth ground by mistake... I get shocked!

Fortunately it is current limited as it uses a resistor to limit current flow but not sure why the inverter references anything to chassis ground in the first place. The HFT inverter I was working with doesn't reference the high voltage to chassis ground.

Will need to investigate this further.