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So your bass has a hum

#41
@moley your post was really helpful and I appreciated reading it.

I stand by my advice of using a ohm meter to see a resistance among the shielding to ensure the connection has been made. I did not realize that we are shooting for zero as any job I have done has indicated a resistance. Any time I was uncertain of shielding being connected, I busted out the ohm meter and saw a resistance. To me, seeing .1-2 is seeing a resistance. A person isn't going to bust out their meter and see zero ohms ever in my experience, so that doesn't seem like good help in a layman's guide. If this was a professional or scientific guide, that would make sense as the reader (and the author ;)) would have a solid grasp of electronics. I will be sure to indicate one will see a low resistance.

@BlueTalon while I appreciate the assistance, your posts have been rather hostile. In the future you might want to avoid phrases such as "how hard is that to understand" and punctuation such as "!?!" It is more destructive to a debate than constructive.
 
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#42
Glad we got it sorted.

For reference, @DiabolusInMusic in other guides I've read on the topic, the phrase used is "you should see a very low resistance, no more than a few ohms". That way it distinguishes between seeing a slight, but effectively "zero" resistance, and say, a few kilo ohms, which is still "seeing a resistance", but which would actually be indicative of a problem.

I think you've hit upon one of the big dangers or lay-person guides - when things don't go exactly to plan, the limited guide often leave holes which can confuse rather than clarify!

Best of luck with the thread :)
 
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#43
DiabolusInMusic said:
@BlueTalon while I appreciate the assistance, your posts have been rather hostile. In the future you might want to avoid phrases such as "how hard is that to understand" and punctuation such as "!?!" It is more destructive to a debate than constructive.
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Trust me, it wasn't hostility. It was exasperation, frustration, and incredulity. And to be honest, your demeanor contributed to it as well, not just your erroneous content. You came across to me as the know-it-all expert who pompously shot down many of the things I had to say, which was doubly frustrating when the basis of what you were saying was as wrong as it was.

DiabolusInMusic said:
If you put an ohm meter to your shielding and your bridge you will see a resistance, that is how you know it was connected. Adding shielding with a resistance of zero ohms would do nothing seeing as the body already has a resistance of zero ohms. 1.5 is not zero ohms, in fact, it is light years away. Zero ohms would offer zero shielding. The resistance doesn't need to read 10000 ohms as .1 ohms works just as well as a million.
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I wish you would stop saying you "see a resistance." .1-2 ohms counts as no resistance, zip, zilch, nada. When you say you see a resistance, just using those words, it indicates you see something much higher than zero. When you touch the leads of an ohm meter to shielding, it should read the same as when you touch the leads together, whatever that number is. 0, .1, 1, it doesn't matter.

DiabolusInMusic said:
@moley I stand by my advice of using a ohm meter to see a resistance among the shielding to ensure the connection has been made. I did not realize that we are shooting for zero as any job I have done has indicated a resistance. Any time I was uncertain of shielding being connected, I busted out the ohm meter and saw a resistance. To me, seeing .1-2 is seeing a resistance. A person isn't going to bust out their meter and see zero ohms ever in my experience, so that doesn't seem like good help in a layman's guide. If this was a professional or scientific guide, that would make sense as the reader (and the author ;)) would have a solid grasp of electronics. I will be sure to indicate one will see a low resistance.
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I really hope you do use an ohm meter. You indicated earlier that you don't use one.

DiabolusInMusic said:
I should add I have not busted out a meter when doing a shielding job for years. The job either works or it doesn't and I have enough experience (plus it isn't that hard) that I can visually detect where any shielding or connections need improvement.
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DiabolusInMusic said:
Most TBers using this guide will probably not have a meter on hand, or ever in their life... I have never had an issue that couldn't be visually seen when completing a shielding job.
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They are inexpensive, far more ubiquitous than you imagine, and they don't even have to be very accurate to be very helpful. If people are going to spend the time and money to shield a bass, they owe it to themselves to get one. It's an invaluable tool for this job.
 
#44
Here is my 10 dollar meter with copper tape

IMG_46341_zpsbd6627d9.jpg


You can see 0.7ohms, not even 1 ohm, so that's very low resistance

Same setting on the meter, but with copper paint

IMG_20140220_201145_zps798d01ae.jpg


a little bit more resistance.

I use copper paint out of convenience. Graphite paint has a much higher resistance, something between 20 and 40 ohms
 
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#45
So I'm getting ready to start my foray into this mod, and I'm excited. I'm no electrician, but I have a very basic understanding of the science involved here. From what I can gather, there is no such thing as a partial shilding job. Its either done right, or it will sound the same as pre-shield. If RF can find a way to the cavity, it doesnt matter how small the gap or lack of seal, the RF will get in and cause the same amount of disturbance as pre-shield?

I'm excited to get to use my multi-meter for a new use. Not sure most guys on TB don't own one. A lot of us are pretty handy and tend to carry an electricians worth of gear to gigs, just in case.
 
#46
I have heard of guys noticing the buzzing reduced when they do a partial job, but reduced buzzing is still buzzing so any actual repair is debate-able. I had so many basses hum after being put back together that I now do the covers every time, since then I have never had a bass hum once back together, at least not RF interference. It is a pretty easy job and gets even easier with each time you do it, if you like Fender as much as I do, you get a lot of practice.

I suppose in theory you would need to cover every single gap to complete the shielding but I do not do wire cavities and there is no discernible difference in when my amp is running with no bass plugged in or with a bass plugged in, I don't think it gets any more silent than that. In fact, the P bass in the guide that was done with aluminum foil tape had no foil on the top of the pickup cover, no ground wire to connect the shielding (although it must have made contact somewhere) and no tack soldering to complete continuity between pieces. Aluminum tape does not have conductive adhesive. That P bass was just as silent with the aluminum job as with copper and paint job.

As obviously pointed out, I am not electrician either, but it is so easy anybody can hack it. Worst case scenario, the bass still hums when it gets put back together, nothing can be harmed and nothing can explode. I would imagine you can diagnose your issue without even turning on your meter (should you even experience one.)

Best of luck with it all. I have taken to buying my copper foil off ebay, you can get it pretty cheap just ensure you buy double side conductive tape. It is still far cheaper for me to by my Supershield locally.
 
#47
The job I'm going to do is on a bass with sealed pickups. Maybe I'll put some tape on the outside of the covers below the pickguard line... Thanks for the info. The pickups are not original to the bass, so if my shield job doesn't work and I have continuity then I may just replace the pickups... We'll see. Thanks again and I'll report back once I'm done.
 
#54
So weird. I'm on my gig tonight. My 210 has a nasty buzz in its 5 1/2" horn at home. So bad that I turn it off. On the gig, it's quiet. Real quiet even w amp turned up. I should have brought the offending bass just to see if it also is quiet here. Electricity is so confusing! I must have a RF factory under my house!
 
#58
And of course I had to test out my rig at home. Amp was silent. Tweeter too. Guess I must have had my laundry room fluorescent light on yesterday. I guess... Bass still was noisy and got quiet when I touched the bridge and strings so I'm still going to shield it. I'll give my results with pics when done.
 
#59
bassman_al said:
From what I can gather, there is no such thing as a partial shilding job. Its either done right, or it will sound the same as pre-shield. If RF can find a way to the cavity, it doesnt matter how small the gap or lack of seal, the RF will get in and cause the same amount of disturbance as pre-shield?
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bassman_al said:
Maybe I'll put some tape on the outside of the covers below the pickguard line... The pickups are not original to the bass, so if my shield job doesn't work and I have continuity then I may just replace the pickups...
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MovingPitchers said:
I'm guessing using shielding paint in the cavities will only do part of the job?
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It helps to know what the purpose of shielding is. What you are trying to do is intercept any EM energy not coming from the pickup(s) and shunt it to ground so that it does not impact the signal from the pickups to the jack. To do that, you want all of the interior surfaces of bass control cavities and pickup routes to conduct as much as possible. You are trying to create a faraday box. A faraday box completely isolates whatever is inside from signals and energy from outside. To do that, it must be complete, or as close to complete as possible. You don't want to leave a hatch open on a submerging submarine, and you don't want to leave openings in the shielding on your bass in todays EM environment.

An incomplete job on your shielding makes it ineffective at best, and turns your bass into an antenna at worst. Everything, all interior surfaces, must be shielded, and everything must be connected to everything, and everything must be grounded.

The only place that should be exposed should be the open face of the pickup routes. Some people even shield that by shielding the inside of pickup covers, or use fender or Rickenbacker type "ashtrays", but it isn't necessary. If everything else is done correctly, the shielding on all other surfaces of the pickup route will be enough. For example, an ungrounded shielded pickup route can act like a radar dish, efficiently reflecting EM energy right to the pickup (this is a bad thing). On the other hand, a properly-grounded fully-shielded pickup route will act more like a baseball backstop -- the energy doesn't bounce back, it just kinda stops.

A proper shielding job will include shielding the wire channels between the pickup(s) and the control cavity. On a P bass, it isn't really an issue, because it's all the same cavity. On a J, or any other bass that has a drilled hole between the pickup route and the control cavity, it requires some additional attention. This is a point on which the OP and I disagree, but it is my opinion that it is preferable to shield those wire channels than it is to ignore them, or to address the issue by replacing pickup wires with shielded wire. The risk of damaging the pickup just isn't worth it IMO.
 
#60
DiabolusInMusic said:
I'd hook them up first and see if they will even require shielding. I am not saying they won't, but they might not. Could save you an hour (or more) of your life and it only takes a couple minutes to hook up P bass pickups.
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This kind of thinking invites problems. If you enter into a shielding job with the priority being "how much time can I save", your priority is in the wrong place.

The priority must be to do a complete and perfect shielding job, however long it takes. For a person doing their first shielding job, it doesn't matter if it takes all day, or even two or three days, as long as the end result is complete and perfect. It's a learning experience, and the person will learn what steps are necessary, and how to do them quicker, and that person's third or fourth shielding job will take a lot less time.

100% of the time taken to do a shielding job is an investment of time, no part of it is a waste of time. The first few jobs might be just as much an investment in one's own education as it is an investment in actually shielding the bass. Even though there might be a lot of "wasted motion" or "wasted time" in the sense the shielding job could have been done more quickly be a more experienced person, that time is still a worthy investment.

Recommending that someone might not need to shield a bass, in order to save them an hour of their life, is very short sighted. There are enough examples of people experiencing different levels of signal interference in different places, that it should be obvious that a single test of a pickup in a single location is not enough to determine whether or not the bass would need shielding. If a person is into his bass as far as replacing a pickup, and is contemplating a shielding job, then that person should do the shielding job.
 
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