Last night I almost died - literally

[~tl]

It depends on the power draw of your amp. This is usually written on the back. Divide that by 230 (mains voltage) and you will have the current your amp requires. You should use the nearest size fuse bigger than that. Basically, the common size fuses relate to the following maximum power draws:

13A = 2990W.
5A = 1150W.
3A = 690W.

Note that this is the mains power draw of your amp, NOT the output wattage which is typically lower. Just checked and my Hartke practice amp draws 1A (or 230W) while only delivering 35W of output power.

Oh, and glad you're all right mate! Will make sure I pack my RCD next time I gig!

Edited October 16, 2008 by ~tl

[woolleydick]

For the gig tmrw I will be using the Rolan Microcube (runs on 9v so is isolated, plus my wireless system. No vocals for me until we establish exactly the source of the problem.

[Stingray5]

I use an RCD plus I usually go wireless depending on the venue/gig itself. (...also one less cable to trip over too! )
Not sure if this has been mentioned but one other thing to check is that your 13amp mains plugs are all 'sleeved'.
I was playing a function at a college in Cambridge a couple or so years back and they required the band to have a PAT test carried out by an electrician before we even set up. A couple of bits of kit (mine and the guitarist) had older non-sleeved plugs fitted. The cables were hard-wired to the equipment so we couldn't simply use a different mains lead. I had a couple of spare plugs in my kit box but only one of those was 'sleeved', the other was an older type.
The electrician would only pass whichever unit I fitted the newer plug to. Needless to say when I got home, I checked all my plugs were of the 'sleeved' type. One or two plugs on older bits of kit were not.
It's a small point but worth checking and being aware of.

[Mrs Tinman]

Flippin' heck WD, what a dreadfully scarey thing to happen

I'm so glad you're still here to tell the tale, and I'm sure the valuable advice on this thread will save others too

[Prosebass]

Glad to hear you escaped from what could have been a fatal incident.... :wacko:
As an electrical engineer some of the things I see amaze me.....mains cables taped up, incorrect fuse ratings, overloaded sockets, extension reels not run out, no RCD devices, etc etc.

If you are a gigging band you should get your equipment PAT tested if only for insurance purposes, just think of the consequences if it happened to a member of the audience. Going completely wireless is the safest way by far, but if cost is prohibitive at least get your guitars to a tech and have the earths removed from the bridges or at least a safety device ie a di box, or a capacitor, (seek professional advice on this)
A simple check can be made with an inexpensive neon screwdriver tester where you can check for mains voltage on all your exposed metal equipment before using it.
I have had more electrical shocks than I care to remember and so know what a shock to the system can do.
Treat this as a warning and take appropriate action....glad you are still with us mate...others haven't been so lucky.

[alexclaber]

[quote name='~tl' post='307906' date='Oct 16 2008, 02:32 PM']It depends on the power draw of your amp. This is usually written on the back. Divide that by 230 (mains voltage) and you will have the current your amp requires. You should use the nearest size fuse bigger than that. Basically, the common size fuses relate to the following maximum power draws:

13A = 2990W.
5A = 1150W.
3A = 690W.[/quote]

Note that many amps will have much higher inrush current when switched on, as the capacitor bank goes from empty to full in very little time, so a standard 5A fuse could be blown by a typical bass head. To avoid this you should use a slow-blow 5A fuse which allows much higher instaneous peak current. Any amplifier manual should cover these details.

I've always know that I should use RCDs at gigs but have been too lazy to use them. Having read this thread I'll be sure to use one in future. I am left wondering whether an RCD on the bass amp would have prevented this - was the current coming from the bass amp and through the bass or from the PA and through the mic? Probably the latter methinks...

Alex

[~tl]

[quote name='alexclaber' post='308520' date='Oct 17 2008, 12:39 PM']I've always know that I should use RCDs at gigs but have been too lazy to use them. Having read this thread I'll be sure to use one in future. I am left wondering whether an RCD on the bass amp would have prevented this - was the current coming from the bass amp and through the bass or from the PA and through the mic? Probably the latter methinks...[/quote]
I would think it would be due to a difference in potential between the "earth" of the bass and the "earth" of the mic. So the current path is something along the lines of PA -> mic -> person -> bass -> amp – or the other way around depending on which is the higher potential, and whether you are talking about regular or electron current .

It would be fair to assume that an RCD on [i]either[/i] would trip in that situation. It's probably a good idea to keep an RCD on anything you can control at a gig – you might not be able to get them to put an RCD on the PA, but if you have one on all your equipment then you're reducing the chance of something like that happening.

[Kirky]

All very terrifying - glad you made it through!

Sorry to be a bit dim (no pun intended), but what do you mean by a 'sleeved' mains plug.

[markytbass]

Glad you're ok, it could have been so different. The bassist I was replacing in a band last year had a belt of a dodgy PA and a guy who was playing at a wedding reception wasn't so lucky. I have an RCD for my amp but you really need everything protected.

[Guest]

[color="#FF0000"][size=4]No one mentioned martindale ring testers, they cost a few quid basically you plug it in to the socket and it tests the wiring is ok. Stops you plugging into a badly wired socket in the first place!
[/size][/color]
[url="http://www.hse.gov.uk/electricity/socket1.htm"]http://www.hse.gov.uk/electricity/socket1.htm[/url]

Edited October 18, 2008 by steve-norris

[YouMa]

[quote name='waynepunkdude' post='307582' date='Oct 16 2008, 08:33 AM']Holy f*cking sh*t.


Glad you are OK man, where do I get an RCD from?

When I played guitar I went to a rehearsal studio and a Marshall JCM800 gave me a shock and the guy assured me it was fine but we said no and left, I'm glad we did now.[/quote]
Wilkinsons a fiver.

[Stingray5]

[quote name='Kirky' post='308724' date='Oct 17 2008, 04:26 PM']All very terrifying - glad you made it through!

Sorry to be a bit dim (no pun intended), but what do you mean by a 'sleeved' mains plug.[/quote]

Look at the two shorter pins (live and neutral) of any of your mains plugs and they should have a plastic 'sleeve' wrapping, usually black, going about half-way up the pin. The longer 'earth' pin is not sleeved.
To be fair, mains plugs have been of the 'sleeved' type for quite sometime now so it's entirely possible you already have them fitted.
Worth checking though.
Cheers.

[s_u_y_*]

Glad to hear that you're alright. Scary stuff.

[silverfoxnik]

[quote name='Mrs Tinman' post='308481' date='Oct 17 2008, 11:55 AM']Flippin' heck WD, what a dreadfully scarey thing to happen

I'm so glad you're still here to tell the tale, and I'm sure the valuable advice on this thread will save others too [/quote]

+1

I've copied this story and all the invaluable advice in this thread onto an email and sent it to myself and the other members in my band so that we can avoid the same thing happening to us.

Thanks for sharing the story with us WD and I'm glad that you're OK

[OldGit]

"get your guitars to a tech and have the earths removed from the bridges" eh? Won't they then buzz like boogery?

[tauzero]

[quote name='Stingray5' post='309041' date='Oct 18 2008, 04:18 AM']Look at the two shorter pins (live and neutral) of any of your mains plugs and they should have a plastic 'sleeve' wrapping, usually black, going about half-way up the pin. The longer 'earth' pin is not sleeved.[/quote]
Just to give a background to this:

UK mains sockets are shuttered - you can't just stick something into the holes when there isn't a plug in. The earth pin is longer than the other pins - it is therefore the first pin in, and when it goes in, the shutter is raised on the other two pins.

At this point, the earth pin is in contact and the tips of the other two pins are also in contact. There's plenty of room under the plug body for someone to slip a finger in. The old plugs had live and neutral pins which were solid, completely exposed brass, so it was quite easy to put a finger on the live pin and be earthed at the other end, and to die as a consequence.

[Stingray5]

[quote name='tauzero' post='309613' date='Oct 19 2008, 12:37 AM']Just to give a background to this:

UK mains sockets are shuttered - you can't just stick something into the holes when there isn't a plug in. The earth pin is longer than the other pins - it is therefore the first pin in, and when it goes in, the shutter is raised on the other two pins.

At this point, the earth pin is in contact and the tips of the other two pins are also in contact. There's plenty of room under the plug body for someone to slip a finger in. The old plugs had live and neutral pins which were solid, completely exposed brass, so it was quite easy to put a finger on the live pin and be earthed at the other end, and to die as a consequence.[/quote]

Thanks for expanding on that, tauzero. I knew someone more qualified would probably be able to shed more light on this.

[escholl]

[quote name='OldGit' post='309154' date='Oct 18 2008, 11:59 AM']"get your guitars to a tech and have the earths removed from the bridges" eh? Won't they then buzz like boogery?[/quote]

-shield the pickup cavities

-ground-->100nF capacitor -->bridge

a lot of active, and some passive, basses don't even need to have the bridge grounded these days.

[Kirky]

[quote name='Stingray5' post='309636' date='Oct 19 2008, 02:08 AM']Thanks for expanding on that, tauzero. I knew someone more qualified would probably be able to shed more light on this.[/quote]

Thanks to you both for the info.

[OldGit]

[quote name='escholl' post='309690' date='Oct 19 2008, 10:23 AM']-shield the pickup cavities

-ground-->100nF capacitor -->bridge

a lot of active, and some passive, basses don't even need to have the bridge grounded these days.[/quote]


Ok so what does adding the capacitor do? and should I use a sprague orange cap for best shielding tone?*












* joking

[escholl]

[quote name='OldGit' post='309924' date='Oct 19 2008, 05:15 PM']Ok so what does adding the capacitor do? and should I use a sprague orange cap for best shielding tone?*[/quote]

expensive oil and paper is clearly the only way to go for best shielding tone

but on a serious note, the capacitor will limit the amount of AC current that can flow through, and will completely block any DC current. AC current is more often the problem, and in this case a 100nF cap will limit the maximum current at 50Hz and 250V to about 8mA, enough to make you curse loudly but that's about it (or so goes the theory). Due to the fact that most noise is above that range, and all of it is AC, it will still act as a ground in that sense, and will still "ground" the strings...In fact, if you wanted to be even safer, you could probably get away with a 47nF capacitor, or even none at all with some pickup configurations. Just make sure that it's no larger than 100nF, and can withstand at least 500V AC. (the yellow round ones from maplin are perfect -- it's what i use)

Of course, the body has it's own resistance, which can vary from megaohms to ohms, depending on skin moisture and contact area, but any additional resistance will serve to limit the current even more. This is still no replacement for properly protected equipment, and is only designed to save your life should you be so unlucky -- it shouldn't be solely relied upon (i'm sure that's probably obvious, just thought i'd say it as a warning). The only way ensure nothing ever goes wrong is to get a wireless unit or disconnect the bridge entirely, however this system should keep you from any serious injury.

[Mottlefeeder]

[quote name='steve-norris' post='308847' date='Oct 17 2008, 06:42 PM'][color="#FF0000"][size=4]No one mentioned martindale ring testers, they cost a few quid basically you plug it in to the socket and it tests the wiring is ok. Stops you plugging into a badly wired socket in the first place!
[/size][/color]
[url="http://www.hse.gov.uk/electricity/socket1.htm"]http://www.hse.gov.uk/electricity/socket1.htm[/url][/quote]
The earth connection to the equipment is there to make sure that if there is a fault, the fault current will be high, and will blow the fuse quickly, which disconnects it.

A plug-in tester is fine, provided you know what it is testing. The ones that have three lights on them will confirm that you have an earth connection, but will not tell you whether it is the last strand of a frayed cable (no use at all) or a thick cable with good connections at both ends.

When you turn up at a venue, any test device that does not measure how good the earth is (earth fault loop impedance) is probably no help to you at all. Granted, it will tell you if there is no earth at all, but then so will your plug-in RCD which will not latch in.

[Mr. Foxen]

So I bought one of the jobbies from Maplins on Saturday, and was all packing up my stuff to take to practice tomorrow. Busting open the packaging and the edge of the plastic gashes my palm. Proper, 'ooh,look at the cut edges, just shallow enough there's no blood. No, wait, theres the blood.'.

Also, why is this not stickied?

[Linus27]

WOW, scary stuff but very pleased you are ok.

I have played bass for around 20 years, 10 of those years giging and I have never owned an RCD. Very scary thinking about some of the dodgy venues I have played in. I think its now time to buy one. I never liked doing backing vocals so this could be a good excuse to not do them

[Dmanlamius]

Actually, this is quite common!

Apparently a lot of musicians die a year from shocks. I've had a "couple" (normally touching bass strings to mic stand) but nothing in the region of what you had to go through.

Really, really glad you are ok.