Badly electrocuted at practice last night - how? why??

Sebber · 2012-10-03T12:00:59+00:00

Hi guys, Need your help identifying what could have caused this. Last night at practice I hauled out my AC30 that's been unused and gathering dust for at least the last year or so. It had been crackling and spluttering last I'd used it and the quote I'd got from Turnkey for repairs was ridiculous. Anyway, I figured I'd give it a whirl and fired it up, and after some initial crackling, which went away after a minute or so of playing, it sounded great, better even than I ever remembering it sounding! So after warming up, we get ready to fire off the first number: while muting the strings with my left hand, I reach for the mic to adjust its position with my right hand and BAM!!!! - I'm being vigourously and extremely unpleasantly electrocuted! I couldn't let go of the mic, so I took a few steps backwards, basically trying my damnedest to get away... the mic stand then tipped over, as did I (landing on my arse), and that released me from my involuntary grip on the mic. My right hand, where I was gripping the mic, is now mildly but uncomfortably, burnt from the shock. I'm far from well-versed in the lore of electrical engineering, but needless to say it was so unpleasant that I sure as damn it don't want it to happen again. I know some of you guys are technically much smarter than me on the inner workings of amps, transformers and all that hokum. What could have caused this and how do I make sure I don't get fried again? Thanks in advance for any pointers, advice or guidance you can offer!

AlanRatcliffe

exsanguinator wrote is there really an unearthed 240v amp on the market here?

No, I don't think that's the issue (at least not with any newish amp). We're getting the 230V "Export" versions of amps and the EU/UK regulations are stricter than most. However, the plug issue negates it. I suppose the government should regulate the plugs on new gear too.

I know of at least one importer who replaces the plugs on the IEC (Kettle plug) cables before they send them to shops. But I've also seen amps in demo rooms that were using two pin adaptors and the amps were unearthed, noisy and dangerous.

Big-G

In the past 2 years, I've bought 6 power amps from a well known brand, and a well known retailer, and all these amps came supplied with the american 2 pin plugs fitted, even though the units are 240v versions. These amps all came with hardwired leads that cannot just be swapped out like the 'kettle' leads can, so anyone who's unable to replace a plug themselves would be forced to use the american type socket, for which I've never seen an adapter for that includes an earth. I've only seen plastic molded adapters, and although they may have three pins for plugging into the board, the earth pin does not form a connection at all.

Apparently, it is illegal for them to sell them with these plugs on, and only twice was I given a proper plug (which I had to fit myself) with the amp. Thankfully, I'm quite handy with a pair of side cutters and reasonably technically minded, so it wasn't a problem for me to lop off and replace these, but as said, not everyone is able, and this can only lead to incidents like this occuring all too often!

Cheers
G!

exsanguinator

Big G wrote In the past 2 years, I've bought 6 power amps from a well known brand, and a well known retailer, and all these amps came supplied with the american 2 pin plugs fitted, even though the units are 240v versions. These amps all came with hardwired leads that cannot just be swapped out like the 'kettle' leads can, so anyone who's unable to replace a plug themselves would be forced to use the american type socket, for which I've never seen an adapter for that includes an earth. I've only seen plastic molded adapters, and although they may have three pins for plugging into the board, the earth pin does not form a connection at all.

Apparently, it is illegal for them to sell them with these plugs on, and only twice was I given a proper plug (which I had to fit myself) with the amp. Thankfully, I'm quite handy with a pair of side cutters and reasonably technically minded, so it wasn't a problem for me to lop off and replace these, but as said, not everyone is able, and this can only lead to incidents like this occuring all too often!

Cheers
G!

perfectly legal in US as they use the old supply-neutral method of earthing....the feed from the distribution transformer uses a combined neutral and grounding conductor
which is problematic and why we always read of hum problems that side from musos
We use the Multiple Earthed Neutral (MEN) earthing system. The combined neutral and earth occurs between the nearest transformer substation and the service cut out (the fuse before the meter). After this, separate earth and neutral cores are used in all the internal wiring
They are busy upgrading their systems.but youd have to go far away to blikkiesfontein in RSA to find a place as old as a normal place in the US,thats why there are lots of electrical fires,electrocutions and..HUM... that side

Sebber

Just an update on this: the bass player's office where we practice was checked by an electrician and apparently he found an earthing problem. I'm not sure if the earthing issue was specific to the power outlet that I was using with my amp but we had my electric shock therapy (band prac) again on Tuesday and I'm pleased to say that it didn't happen again. I didn't use the AC30 again, I'll be getting that checked out too.

I do however now have what feels like a perfectly rational terror of touching my mic: thanks to a dude on another forum for the top pro-tip of using the back of the hand to touch the mic so that if you do get DC-zapped your muscle contraction will automatically move your hand away from the mic!

henrebotha

exsanguinator wroteHigh Voltage shocks but does not kill,
But high amperage kills on low voltage as well

You clearly know a lot more than me about power, so I'm not going to challenge anything else you said, but I'm going to explain this bit for the benefit of other people, who might not be aware of how electricity works.

Current and voltage are two sides of the same coin. It's like saying that it's not the force with which a bullet enters your body, it's the bullet itself that kills you - which is obviously false, since a bullet cannot enter your body without sufficient force, and even a tiny-ass bullet can kill you if it hits you with enough force.

Electricity through your heart will kill you. Whether the electricity is of barely enough amperage but high enough voltage to overcome your body's resistance, or low voltage but high enough amperage to overcome your body's resistance, is of no consequence. The only non-lethal shock is one of low voltage AND current. (Excepting that weird in-between state where a shock can actually prevent your heart from entering a state of fibrillation... in which case, as long as the voltage isn't so high that it causes other injuries like burns, you're likely to escape unscathed! Science, yo.)

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