See you next month by the way
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| Earthing a tune-o-matic bridge http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=11876 |
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| Author: | forestcaver [ Wed May 02, 2007 3:33 am ] |
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I am building an electric, like a Les Paul, out of sycamore. (See http://www.aurw79.dsl.pipex.com/guitar if interested). However, I am unsure how people wire up the earth. I am planning on shielding the control cavity with copper foil and earthing everything to that. BUT how important is it to earth the strings/bridge ? How do you get access to a tune-o-matic bridge - drill through to the post holes from the control cavity ???? Do Gibson earth the bridge ? Any help is gratefully received.... Cheers, Andy |
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| Author: | Howard Klepper [ Wed May 02, 2007 3:45 am ] |
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[QUOTE=forestcaver] I am building an electric, like a Les Paul, out of sycamore. (See http://www.aurw79.dsl.pipex.com/guitar if interested). However, I am unsure how people wire up the earth. I am planning on shielding the control cavity with copper foil and earthing everything to that. BUT how important is it to earth the strings/bridge ? How do you get access to a tune-o-matic bridge - drill through to the post holes from the control cavity ???? Do Gibson earth the bridge ? Any help is gratefully received.... Cheers, Andy[/QUOTE] 1)very important 2)yes 3)yes |
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| Author: | forestcaver [ Wed May 02, 2007 4:17 am ] |
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Thanks for the reply - I really wasn't sure at all as this is my first electric build... Cheers, Andy |
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| Author: | Richard_N [ Wed May 02, 2007 7:29 am ] |
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Andy Earthing the strings is essential. With a T.o.M. you can drill a small hole for the earth cable thru to the hole where one of the bridge mounting ferules will be pushed in. You then need to insert the earth cable before you push the ferrule into its hole. Then when you push the mounting ferule in place it clamps the earth wire and ensures a good earth via the strings. Hope thats clear ??? |
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| Author: | Richard_N [ Wed May 02, 2007 7:39 am ] |
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See you next month by the way
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| Author: | martinedwards [ Wed May 02, 2007 9:04 am ] |
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yup, that's EXACTLY what I did making this....... 
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| Author: | forestcaver [ Wed May 02, 2007 11:33 pm ] |
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Thanks for that Dickie ! (I did a double take - took me a while to work out who it was !). See you next month ! Looking forward to seeing your band and what you've made recently... A. |
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| Author: | JBreault [ Thu May 03, 2007 1:58 am ] |
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Andy, your guitar is comming along very nicely. Don't forget to post pictures here when it is done. |
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| Author: | Dave-SKG [ Fri May 04, 2007 2:21 am ] |
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In the old days (1970's o.k.)we used to lift the ground because of polarity "shocks" with the microphone/pa system when your lips touched the microphone. I DON'T recommend that at all. You will have to search the web for details ( or ask Frank Ford or Dan Erlewine) but the modern way is to put some type of a resister/capacitor/whatever the heck it is, in the ground path and this way it alleviates the minor "shocks" from PA systems but still protects you from high voltage death. I don't know the details (obviously) but have read about this several times. If you find this info please post it so we can all evaluate. Check Below I found some info...I don't know how reliable this info is maybe one of our electrician builders will chime in to validate/dispute. |
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| Author: | Dave-SKG [ Fri May 04, 2007 3:06 am ] |
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o.k. here's what my research has found...from "Guitar Nuts"...this is directly from their site. I highly recommend you all read the entire article on electrical shock...shock hazards This is what they recommend: "Use a wireless system on your guitar. This will protect you completely from shock scenarios one and two and from the most lethal path of shock scenario three. The absolute safest way to go is with a wireless microphone and a wireless on your guitar. Disconnect the bridge ground wire on your guitar or use a small (about .02uf) capacitor shunted by a large (about 220k) resistor to isolate the bridge from the rest of the ground. Note that this may significantly increase the amount of hum you experience. Also note that this is only a partial fix – the jack plate and some other exposed metal parts (including metal volume and tone knobs) of your guitar and amplifier will still be potentially lethal. Use only modern equipment with three-prong grounded plugs. Never use ground lift adaptors or switches on the power connection. Never use polarity switches. When practical plug all of your equipment into a single outlet at the venue by using a power strip or power conditioner. This way at least all of your equipment will be at the same potential and polarity though you still have to be very cautious about other equipment. Obviously, you can't do this if you've got a lot of high-power equipment. If you are gigging, a top-notch power conditioner is a good investment anyway because it can help prevent noise from lighting equipment and such from getting into your equipment through the power. Learn to be very conscious of the equipment around you and to avoid touching other musicians, microphones, etc. while touching your guitar strings or bridge. Again, you're still an electrocution looking for a place to happen. Wear rubber soled shoes. Again, you're still an electrocution looking for a place to happen. Test the outlets at each gig with a checker and finally test by holding your guitar strings against the microphone and anything else that you are likely to touch while performing (with all of the equipment powered up, of course). This doesn't fix the problem but at least you'll know when you need to get right with God before starting the first set. Never use your body as a piece of test equipment. During the discussion on rec.music.makers.guitar one sadly misinformed individual recommended touching the microphone with one hand while holding the guitar strings with the other (to avoid being surprised by a painful shock on the lips). After several of us recovered from the heart-attacks caused by just thinking about that we explained to this individual that what he was recommending was the most lethal shock scenario possible because the path for the current goes straight through the heart. It is current through the heart that kills. People have survived high voltage shocks that, for example, travelled from wrist to elbow and severely burnt the arm. I've personally taken 115V 400hz shots from fingers to elbow several times with nothing more serious than, "ouch, that hurts!" and a temporary numbness. I know a guy who took a very high voltage (in the thousands) shock through his head . The shock caused severe injuries and he spent months in treatment and reconstructive operations but he survived. Yet many have died from a relatively mild shock that left no marks but routed a few milliamps through the heart. One of the first things taught to new electronic technicians is the "one hand principle" – one hand should always be in your pocket when the other is inside "live" equipment. If you ever have occasion to play an outdoor venue where power is supplied by portable generators it is extremely important that you check your power sources. In this case you should not only check the outlets with an outlet tester, you should also confirm that the generator is properly grounded via grounding rods, water pipes, etc. This is important regardless of whether the power is being supplied by a tiny "personal" generator or by a large diesel generator on a trailer. Generators must be grounded! A while back a friend told me about an outdoor gig he played a few years ago. It had rained the night before and he was standing on wet grass. He kept getting shocked hard enough for it to be painful and he couldn't understand why because his outlet tester was showing everything to be fine. I asked and, sure enough, his equipment was being powered by a generator. I wasn't there but I can guarantee, sight unseen, that the generator was not grounded properly. Don't assume that the generator is properly grounded just because the venue is supplying it and they seem well organized. Quite often outdoor festivals are organized and staffed by well-meaning volunteers who know absolutely nothing about safely operating their rented generator. Finally, note that the 0.33uf capacitor I use to isolate the shield ground from the signal ground in the "Quiet the Beast" modification on the wiring pages should not be relied upon to protect you from the AC shock of scenarios two and three! I specified this capacitor solely to protect against the much rarer but less easy to detect DC shock of scenario one (scenarios two and three can be easily detected by any musician who cares to protect him or her self). Even with the capacitor, a high DC potential failure will give you a nasty "bite" while the capacitor charges – but the capacitor serves to limit the duration and severity of the shock. In shock scenarios two and three the 0.33uf capacitor may reduce the severity of a shock to below lethal levels for most people but don't stake your life on it! You could replace this capacitor with a much smaller one (about .02uf) which would protect against both the AC and DC shock but you can expect the result to be noticeably noisier – and other parts such as the jack plate will still be at a lethal potential. The bottom line is that you should protect yourself by ensuring that the mains wiring at every venue you play is correct. It's incredibly simple to check the mains and, at least in the US, local government agencies will happily force venues to comply with wiring codes. There is simply no reason to risk your life unnecessarily by relying on marginally effective secondary protective devices. " |
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| Author: | forestcaver [ Sun May 06, 2007 8:51 pm ] |
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Thanks for all the replies - it's really useful. Cheers for the kind words Joe - I'll post some piccies when it's done... Cheers, Andy |
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