ELECTRICITY IS DANGEROUS!

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

tony dB

Well-known member
Joined
Jun 4, 2004
Messages
1,304
Location
Belgium
and i know,

replaced a fuse in an active 240 volts preamp holding both ends with each hand. I had a very :evil: massage from hand to hand passing chestmuscles etc...
still feels a little dodgy in my right forearm ... I can see a little blue trace and it feels like a broosed (eng?) spot in my arm.
I survived, but just wanted this to report, if i was standing barefoot it would probably been a lot worse!

Never thought this would happen (again), but sometimes we can get so exited of finding the solution to a malfunction, that being carried away makes us (well ME) make mistakes.

Don't let this happen to you,

ALWAYS UNPLUG FROM MAINS WHEN TOUCHING HIGH VOLTAGES CIRCUITS INSIDE GEAR OR PCB'S!!!

Chocky T.
 
Jaakko,

I needed both hands to fit the fuse,
silly me forgot it was still plugged into 240V

Lucky i wasn't touching any of the valvestuff inside :cool:

Tony
 
And with "valvestuff" always measure the B+ voltage before you touch something! If there are no bleeders there could be high voltages there for hours.

Best regards,

Mikkel C. Simonsen
 
Ouch!

It's too easily done, which is why it's best to check and double-check that any mains supply is disconnected. Good tips from Jaako and Mikkel there.

The most stupid mains shock I had was from a guitar amp. I removed the panel-mount fuseholder to replace the mains fuse, and accidentally touched the collar of the fuse holder and received a hefty shock. Upon further investigation, the manufacturer had connected Live to the front tag of the fuseholder and not the end tag, which is the safest practice. ALWAYS unplug before investigating ANYTHING. I was pretty shaken up, but the worst injury was actually my thumbnail- as I pulled my hand away during the shock, the jolt made me whack it against something and ripped it half off. Not a pleasant experience.

I've given up on shocks nowadays- I'm older, wiser and slightly more cautious now!!

:shock:

Glad you're okay, and it's good to share shocking experiences- it makes you respect the power of the electron!

Mark
 
I know that it id bad practice but sometimes you have to work with the power on to find a fault - experimenting with earthing or rotating transformers whilst listening. Or just checking to see if voltages are as they should be.

I usually wear rubber gloves & thick sole boots for this, and I always run new gear with a powerbreaker on the plug until I have had it long enough to trust it.
 
:grin:

and goggles too, don't forget goggles when powering things up. I haven't had a cap explode yet but I know others here have.

Like may of us here I got started off building 9V stuff and then moved up. On my first tube build - an altec preamp thing - I couldn't get it to pass audio. Gave up and went to the pub for a bit.... by 1 AM I had zapped myself three times from the 300V B+ caps (even though the power was off) and also go it working somehow! A really stupid dumbass thing to do.

More importantly I scared myself into believing that this stuff is dagerous. I also flicked some solder onto my eyelid this year which burnt the eyelashes. Talk about a near miss.

So, gloves, goggles, powerbreaker and boots.....
 
Oh yea,

I forgot about the old molten-solder-flying-towards-eyeball thing! It's one of the hazards of point-to-point when you desolder a component and forget that the lead you've got in the other hand is under tension...

:roll:

I learnt the terrifying power of electricity in my teenage years fooling around with an old microwave oven transformer....highly NOT recommended... :shock:

Mark
 
[quote author="zebra50"]and goggles too, don't forget goggles when powering things up. I haven't had a cap explode yet but I know others here have.[/quote]
Just do what I do - duck and cover! - and use a "remote trigger"... :green:

Best regards,

Mikkel C. Simonsen
 
I had a cap explode a couple weeks ago when I was messing with making a power supply out of junk box caps.

I'm still not 100% clear on why it did... I had been using some huge 1000uF 35V caps to filter the rectified AC, and that worked great, but they were HUGE! I also had some teensy little 100uF 50V caps, and I figured they wouldnt work as well (smoothing wise), but wanted to see what the output looked like for comparison's sake. I hooked it up, powered on, and it was like a damn firecracker went off.

It's possible I may have had it in backward, but I don't think so. What else could the problem have been? Heat boiling the electrolyte?

At any rate, that was a fun and scary experience :) I was already a bit jumpy because I was working with mains.
 
I think I've got you all beat for *s-t-u-p-i-d* self-electrocution!

When I was about 15, I had an 'MK' power plug which I'd had to replace a fuse in. (UK power plugs have removable backs, with fuses inside). I hadn't screwed the back on very well, and the screw -over time- loosened until the back was close to falling off... I somehow never got round to tightening up the screw!!!

One time, I went to pull the plug out of the socket (the socket had no power-off switch) and the back came off in my hand. I was leaning diwn, supporting my weight somewhat with my right hand, leaning on a (grounded!) metal radiator. I decided that since the back had fallen off the plug, I'd just leave it plugged back in and unplug something else instead! (Am I lazy or what!?!?!??!!)

...so -still supporting my weight on the radiator with my right hand, I pushed the three pins home with my left thumb... :shock: :shock: :shock:

Ground... no problem...
Neutral, -easy.
Live...

:shock: :shock: :shock:

Yeeee-Owwch!!!!!!!

240VAC very well-connected, across the chest... -I can still feel it today!

However, that doesn't beat the local guy who died yesterday... wiring up christmas decorations outside in the grass... barefoot... with the sprinklers running!!!!!!!

-Dumbass! -almost as dumb as me!!!! :sad:

Keith
 
My worst shock was from a 10uF cap that was charged up to about 400v.
I was using the madmans hum/motorboating detection method in a valve amp I was building, by bridging a cap across the various stages. I then put the fully charged cap on the bench WITHOUT discharging it. 5 minutes later I`d completely forgotten about it & accidently lightly brushed the little finger on my right hand across the 2 terminals.

BANG !!! my whole arm & pecs on the right hand side locked solid. I looked at myself in the mirror. I was white as a sheet & had broken out in a cold sweat. A VERY painful experience.
 
I find that story really scary. 10uF caps are small and the temptation is to think that something small can't contain enough juice to do any harm.... :shock:
 
The thing to remember is that Q=CV Although the cap is small the voltage is high, therefore the charge is also highish.

but not compared to a 10,000uF cap with 35v across it like you could easily have in a power amp.

BE WARNED COS IT REALLY HURT WHEN I DID IT !!
 
I was involved in a studio in '87 & there was an electrician working on our supply, live.....

Well, his screwdriver slipped & shorted out 2 phases, or to ground (he didnt remember :shock: ). It took the whole building out & I found the guy wandering around with a completely black arm saying "Hey, I'm OK". Rushed him off to hospital where he spent 2 days on a drip.

After that I was quite grateful that my worst was 220v.

Peter
 
> replaced a fuse in an active 240 volts preamp holding both ends with each hand. I had a very massage from hand to hand passing chestmuscles etc... if i was standing barefoot it would probably been a lot worse!

No, that's about as bad (and stupid) as it gets. Hand-to-hand means through the heart. Hand to foot sends some current down the side of your body, less through the heart. (But that can still be fatal, even on less-deadly 120V USA power.)

> still feels a little dodgy in my right forearm ... I can see a little blue trace and it feels like a broosed (eng?) spot in my arm.

"bruised". Damm if I know why we spell it with "ui" when we mean "oo".

> I found the guy wandering around with a completely black arm saying "Hey, I'm OK".

Your stunned arm and bruise is a small version of what that guy got. Cooked flesh and burnt-out nerves. Yes, enough of that is the same as putting your arm in a fire: if the shock didn't kill you the dead flesh poisons your whole system and you go downhill to death. Recently doctors have got a lot better about keeping fire-burn victims alive (I remember when 20% 3rd-degree burns were fatal), but they know less about electric burns because they are rarer and less consistent.

You survived so far and a bruise is probably not worth showing to a doctor, unless you know an electric-shock Specialist. The numbness will fade in time: my 590V shock across my little finger is 50% better after only 30 years.
 
I put a 1/4" chisel (freshly sharpened and mirror-polished) all the way through my right thumb about a year ago... I still have tinglies in it from time to time... nerve damage sucks :(
 
As a 17 year old squaddie I was given a metal knife and a box of fuses and told to go through all the bed side lights and change the fuses and light bulbs
The bed side lights are all in one contraptions with a push button for on/off running of a 240v supply

So if they have a dodgy bulb you have no idea if they are live or not

First change - as soon as I tried to flick the fuse out of the circuit with my metal knife - it felt like a sledgehammer was applied between my shoulder blades
 
Back
Top