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Shielding - copper tape on scratchplate?


Lozz196
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Quickie question, my 78 Precision buzzes a bit in some places, mainly where we rehearse - probably their rubbish electrics - and want to know if covering the back of the scratchplate with copper shielding tape will help. I don`t want to shield the actual cavities in the bass itself as want to keep it in as original condition as possible.

If it will give a bit of help, anything I have to be careful about, being fairly cack with anything technical/manual?

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[quote name='Thunderbird' timestamp='1397317496' post='2422769']
Dont buy any tape Lozz I bought a bulk lot of aluminium tape fire me a PM and you can have some FOC mate :)
[/quote]
Good idea I have a number of rolls of ally tape left over from a pipelagging job think I will give it a go on my old mex jazz
nice one

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[quote name='Thunderbird' timestamp='1397317496' post='2422769']
Dont buy any tape Lozz I bought a bulk lot of aluminium tape fire me a PM and you can have some FOC mate :)
[/quote]

Thanks Paul, much appreciated.

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technically Copper is a better screen than Aluminium.

Why not use the adhesive copper tape (or aluminium ) to screen the cavities anyway - you can always peel it back off fairly easily to get back to original condition although I can't think why that would be an issue really. Or Ki's copper plates sound a good option.

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This all sounds great guys, didn`t realise that the tape would be easy enough to peel off - like I said, I`m rather rubbish at anything manual/technical.

I`ll see how it goes with tape and if still lacking drop you a call re those plates John.

Cheers all.

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[quote name='alanday1975' timestamp='1397407355' post='2423619']
Having a nightmare with buzzing from my rickenbacker 4003 which only disappears when i touch something metal....Would screening help at all anyone??????
[/quote] I would think so cant hurt :) I have been having this issue with one of my basses myself so would be interesting to see how you go as shielding that particular bass did not help me (:

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[quote name='alanday1975' timestamp='1397462073' post='2424007']
im a bit of novice so just double checking.....So i should tape the back of the scratch plate, the cavity where the pup is and the cavity where the pots are yeah??
[/quote]

Yep, that's it.

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[quote name='alanday1975' timestamp='1397407355' post='2423619']
Having a nightmare with buzzing from my rickenbacker 4003 which only disappears when i touch something metal....Would screening help at all anyone??????
[/quote]

Something I've encountered a couple of times is this. A couple of basses have developed a serious buzz, which disappears when touching the bridge or strings.
I've removed pickguard checked wiring/earthing etc. all good. With the pickguard still pulled away from the body, I've pushed in the jack plug and no buzzing :blink: . Then put p/g back in place buzzing returns.
Problem resolved by loosening off the input socket and rotating it slightly, so that the metal work is not in contact with or near to the side of the cavity.

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  • 2 weeks later...

[quote name='hamfist' timestamp='1397408153' post='2423634']
Conductive metal tape does the job. Even though it has been mentioned already I can't emphasize enough how important it is to get stuff with CONDUCTIVE adhesive. If you don't your efforts will be useless.
[/quote]
"useless" is putting it a bit strong (provided that each section is earthed), but the conductive glue certainly helps. Even so I tend to put a few spots of solder on the joins!

As someone has said, copper is technically better than aluminium (about twice as conductive), but also has the advantage that it is easily soldered.

Personally I wouldn't bother doing it unless you were do the whole cavity as well, it will be far more effective than just doing the scratch plate. Take the cavity screening slightly over the top edge, and make the screen on the back of the scratch-plate overlap it so you get near continuous contact along the join.

Did it on my son's Strat and it transformed it.

Edited by Count Bassy
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[quote name='Meddle' timestamp='1398289330' post='2432645']
It is a waste of time anyway *flamesuit on*. Most modders don't bother to differentiate between electromagnetic interference (EMI) and electrostatic interference (ESI). Pickups work great for picking up EMI, because the main constituent part is about 1 km of copper wire. Humbuckers and dummy coils work to cancel out the EMI picked up by a single coil pickup. Shielding a guitar won't do anything to cancel out EMI. If you shield the pickup cavities, you effectively create a metal box without a lid. If it was a fully enclosed box it would become a Faraday cage and then it would block out EMI (but then your pickup wouldn't work). EMI can be reduced a great deal if you have very clean power in your house/studio/venue. EMI will be bad if your house has old wiring, you use a CRT monitor, you use dimmer switches, you have fluorescent lights or an electric motor toiling away in the vicinity.

I only dislike shielding because it has been drummed into the heads of novice builders and modders as a must-do hack. The problem is that bad shielding acts as an ESI enhancer, not an ESI reducer. Furthermore, shielding can kill a lot of high end from your signal if done badly. My best advice is to use shielded cable within your guitar. There are some places (the run from the tab on your volume pot back up to the body of the pot where the shield is soldered on) that will be exposed. You may also have problems converting two-cable pickups into shield + hot cable pickups. Having said that, twisted pair wiring will also cut down on ESI a good deal.
[/quote]

Um, well it acts as a Faraday cage, except that you don't screen in front of the pickups, so you keep out the hum from say 324 degrees round the back up of the pickup, while letting in a small amount of hum, but a lot of signal, from the 36 degrees at the front. This should (and, in my experience, does), greatly improve the signal to noise ratio.

Also the presence of an earthed surface even when not fully enclosed will have some effect because the electromagnetic wave's phase is reversed on reflection so that, particularly at low frequencies (e.g. 50Hz), the incoming and reflected waves tend to cancel out. I guess this might be why some of the cheap skates reckon they can get away with a sheet of aluminium on the back of the scratch plate, although they might also be counting on the player's body to provide some screening from the rear.

You wouldn't normally want to be screening around the sides of the pickup itself as this might introduce enough capacitance to affect the tone (although you might like the affect).

In my experience a very useful enhancement. Certainly not a hack.

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I bought a scratchplate recently which wasn't shielded and my P bass buzzed (which went away when I touched bridge or metal jack plug case). Put my old shielded scratchplate back on.........no buzz. So I bought a sheet of copper shielding foil from a dude on ebay, stuck it to my new scratchplate, fitted it, and the buzz was gone. I thought about shielding the cavitys, like I've done on my Jazz, but it was no longer necessary as the buzzing was just a memory.

This is the guy [url="http://www.ebay.co.uk/itm/121304706142?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649"]http://www.ebay.co.u...984.m1439.l2649[/url]

Edited by gjones
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[quote name='gjones' timestamp='1398480848' post='2434591']
I bought a scratchplate recently which wasn't shielded and my P bass buzzed (which went away when I touched bridge or metal jack plug case). Put my old shielded scratchplate back on.........no buzz. So I bought a sheet of copper shielding foil from a dude on ebay, stuck it to my new scratchplate, fitted it, and the buzz was gone. I thought about shielding the cavitys, like I've done on my Jazz, but it was no longer necessary as the buzzing was just a memory.

This is the guy [url="http://www.ebay.co.uk/itm/121304706142?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649"]http://www.ebay.co.u...984.m1439.l2649[/url]
[/quote]

Excellent result for you. My lads Strat had an aluminium sheet on the back of the scratchplate, and in my case completely screening the box and extending the scratchplate screening made a significant improvement.

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[quote name='Meddle' timestamp='1398470562' post='2434570']
Huh?? A Faraday cage is not something you can have 'a bit of'. You will not reduce EMI by reducing its path into your signal chain into a narrow 36 degree swath.
[/quote]

Well, actually, as I understand it, you can have holes in a Faraday cage proving that the size is small relative to the wave length of the radiation. As and example, A microwave over is effectively a Faraday cage, but the door generally included a metal mesh with holes in it, and a microwave wavelength is typically around 12 cm.

The wave length of a 50Hz EM wave is around 6000Km.......

This is why it is relatively easy to screen for 50Hz, much harder to screen for modern noise sources such as computers.


[quote name='Meddle' timestamp='1398470562' post='2434570']
Again, huh? I think you are giving modders far too much credit.
[/quote]

I wasn't thinking so much of 'modders' as the OEMS, such as Fender (on this mexican strat anyway).

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Well an update, I did it with aluminium tape very generously provided by our very own Thunderbird - thanks Paul - and it is now buzz free.

The only downside, well there seems to be a bees nest near/under the rehearsal room, so there is still a bit of buzzing going on..................

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