how do I check my bass is earthed properly?

[jazzbob]

I've read the sticky on humming and buzzing and think I have tracked down the buzzing I get on my Fender Jazz bass but I don't know what to do next, short of taking it back to the repair shop.

It has a set of Noiseless SCN pickups on but if I use [i]any treble at all[/i] I get what sounds like a constant 'transformer' noise, like being up close to a flourescent light. It stops as soon as I touch the strings, control plate or bridge but it gets weirdly worse if I put my hand/body against the back of the bass opposite the pickups. Of course, its the same when I am playing because the back of the pickups are up against my hip. Its as if the pickups are sending a field out through the back of the bass and they really don't like it when you get close.

I thought of checking the packing behind the pickups and putting something in as a shield (lead or plutonium maybe...) has anybody got any recommendations or ideas about how to cut that 'field' effect down and, by the way, what [i]should[/i] be behind the pickups, if anything?

Also I wonder if the bass is earthed properly, is there a simple way to check (with a multimeter or a canary and a naked flame or something) that does not involve too much dismantling as it is nicely set up at the moment...

Thanks,

Jazzbob

[SJA]

ideally the pickups cavities and control cavity should be lined with screening of some sort-

aluminium or copper foil, or screening paint, connected to ground.

I used Maplin self-adhesive aluminum tape, does the job,

but copper foil is better, plus you can solder directly to it.


re. checking earthing, use a continuity tester or multimeter between the jack socket ground and whatever point you need to test.
sounds like your bridge is grounded fine though.

I'd have thought your Jazz would be fully screened already though- maybe the ground connection to the screen somewhere has come loose.

Edited December 9, 2007 by SJA

[NickThomas]

Lick a shiny bit LOL

[jazzbob]

Thanks,

Licking a shiny bit does help (makes my fillings light up too) but I haven't mastered that whilst playing yet, i'll keep stretching and see how far I get.

In the meantime I am sure there is an earth problem somewhere so I will ask the guy who fitted the Fender SCN's to take another look and maybe see if it is possible to entomb the pickup casing in copper too. I have tested it on two amps now and its the same 'zzzz', really loud if you play an open string and break contact.

Also the neck pickup makes [u]a lot of noise [/u]if you go anywhere near it and one or two of the pole pieces make a real din if you touch them with or even get within a few mm, I think its a duff pickup the bridge pickup actually makes l[u]ess[/u] noise if you touch it. Needless to say, unless this is just a 'Friday afternoon' example I am not that convinced by the 'Noiseless' name tag and will see if I can get some other pickups in there, anyone recommend some? EMG look good but I have not used them before...

Jazzzzzzzbob

[Buzz]

[url="http://basschat.co.uk/index.php?showtopic=194"]http://basschat.co.uk/index.php?showtopic=194[/url]

Stickies might help you.

[SJA]

[quote name='jazzbob' post='101796' date='Dec 9 2007, 05:23 PM']so I will ask the guy who fitted the Fender SCN's to take another look and maybe see if it is possible to entomb the pickup casing in copper too.[/quote]


I meant the line the pickup cavity with foil, not the pickup itself!

[jazzbob]

I know, but I have seen someone earthing a Marcus Miller bass and he [i]did[/i] encase the pickups in copper, it was like some sort of open heart surgery, take a look at Part three:

[url="http://www.talkbass.com/wiki/index.php/Silencing_the_Noise_on_a_Marcus_Miller_Signature_Bass"]http://www.talkbass.com/wiki/index.php/Sil..._Signature_Bass[/url]

I just tried my bass through someone else's amp (I have a Fender Bassman 250/210) and its [i]acceptably[/i] noisy, nothing like my set up, so i am going to ask someone to look at the bass [i]and[/i] amp at the same time.

Jazzzbob

[bassbloke]

what model bass is it?

[jazzbob]

Its a 1992 MIJ Fender Jazz Bass. It now has two new Fender SCN pickups which i think are just letting me hear the problem more clearly rather than being faulty themsleves. I have recently lined the control and pickup cavities with conductive tape which definitely helps a bit but I think the pots are on the way out and the wiring looks very iffy.

I downloaded a wiring diagram from EMG for the jazz bass and it looks nothing like whats inside mine. If I push the neck vol pot at right angles the noise gets really bad ('don't do it then' I hear you say...) while a Fonz-like rap to the scratchplate quietens it down again. Basically I am going to get it rewired and the pots changed whilst saving for something new with good quality electrics.

Jazzzzbob

[Muppet]

Just a thought - check the input jack to make sure it's making a good connection. Only reason I say this is on Saturday night I experienced a really really bad buzz through my Jazz and I managed to track it down to a poor connection between jack and plug.

Hope you get it sorted soon - there's nothing more annoying!

Cheers

Steve