Jaguar build - grounding issue?

Electro_Ham

Jaguar build. The body is complete with all electrics wired in. There's no neck and no strings yet. I thought I'd plug it in just to see if it sort of works. There's quite a buzz coming from the upper and lower control/switch plates when I touch them. The volume/tone/jack plug plate doesn't do this. The routs are shielded with copper tape. I've wired it almost exactly like this:
http://i236.photobucket.com/albums/ff212/larz55_2007/jaguar_wiring_diagram____nov 09_zps0nolegva.jpg

I say 'almost exactly', because the grounds from both upper and lower control/switch plates, have the ground wires tucked under the switch (with the switch screws tightened to hold) and the other ends of the ground wires are soldered to the copper tape. I did not solder the grounds to both of these plates +/- switches.
Could that be my problem? Do I need to solder?

http://i236.photobucket.com/albums/ff212/larz55_2007/IMG_3605_zpsmh8afvbx.jpg
http://i236.photobucket.com/albums/ff212/larz55_2007/IMG_3710_zps4bgig0py.jpg

frankus

If it's all wired up and you have a tuning fork you can use that to see if you get the expected signal from the pickups by holding the vibrating fork over the pickups - it can test the volume control behaviour

in the diagram all the chambers have a wire leading from one to the other and soldered to the bottom of the cavity - how are you ensuring this continuity between chambers? if it's not there you'll end up with several ground points... IIRC

you could just add a strip of tape across the top connecting each cavity to test this theory out.

Electro_Ham

Thanks for the quick reply. I'll try the tuning fork trick later tonight hopefully. Yes, I've got all those routes linked together. Also, I'd have thought I didn't really need to ground the plates to the copper foil since it comes up onto the top surface of the body. I just wanted to be extra safe. The foil has conductive glue and I even painted the routes with shielding paint prior to the copper foil. A total belt and braces approach, so I'm a little dismayed at this moment.

frankus

On the builds I've done, Bass VI and telecasters, when I've shielded I've run thin wires from each chamber into the next and soldered it to the bottom of the cavity.

I try and make sure everything connects to everything else just once to avoid ground loops.

The shielding on the plastic guard doesn't connect to the metal control panels... I use a digital tester to check continuity and resistance.     

ICBM

You've definitely got a broken ground between the jack plate and the switch plates somewhere. Either the jack plate is not connected to the cavity shielding, the cavities aren't connected together, there is a break in the shielding in one of the cavities, or the other switch plates are not connected to their cavity shielding - you should be able to find out with a beep tester.

For what it's worth I never trust conductive glue to make a ground connection, it often doesn't. Always solder across every joint - you only need one spot between any two pieces, you don't need to completely seam it.

Electro_Ham

I got the tuning fork and the switches work as they should. I'm not convinced either of the volumes are working though. The guitar is buzzy as soon as it's plugged in. The buzz just gets more noisy when touching the upper and lower swich plates, the claws and the trem unit. I'll solder and make connections across the different sections of foil. It shouldn't take me long. Hopefully, I'll report back Sunday night. Thanks for the advice chaps.

ICBM

Electro_Ham said:

I'm not convinced either of the volumes are working though. The guitar is buzzy as soon as it's plugged in. The buzz just gets more noisy when touching the upper and lower swich plates, the claws and the trem unit. I'll solder and make connections across the different sections of foil. It shouldn't take me long.

The ground connection to the strings via the trem or bridge is also missing. That sounds like a lack of ground from the jack plate to the volume control or the next point along. If the zero terminal is not grounded the control barely reduces the volume when it's turned down. If the jack plate is grounded (it most likely will be since the jack bushing goes directly through it) and the connection to all the shielding comes from the volume pot, it could be that the volume pot casing is not connected properly to its bushing. Sometimes the riveting fails to make a good electrical contact, and you need to squeeze it tighter.

Check with a meter before you try to do anything, it will probably be something simple and it's worth finding out where the problem is before you accidentally fix it but don't know how, and then it comes back later .

Electro_Ham

Thanks again. I've got a wire from the trem to the lowest cavity. I'm pretty confident in my soldering and I followed the diagram above to the letter. Lets hope it is something easy. I'll borrow a meter and work through things systematically.

Electro_Ham

Hi chaps. I got a loan of a multi-meter. Set to test continuity. I'm getting beeps so there is continuity all over the different pieces of copper shielding from the top controls to the bottom and everything in between, including the trem. I did notice that the readings were anywhere from 000 to 012.
I'm no expert on multi-metering - I don't really understand it. I have noticed that I get readings of 000 from the jack plug ground to the copper shielding, that's just one piece of wiring. I get a reading of 012 from the trem to the farthest away piece of copper shielding up in the upper switch cavity, which is a few pieces of foil and a few links of wire away.
As a noob, do I want 000 readings throughout the guitar? Could this be the issue?

ICBM

Yes, you need 000 readings throughout. Anything higher and you have poor ground continuity.

My guess would be the conductive glue on the foil, since a bad mechanical contact between two metal parts will *usually* just go to a complete open circuit.

Check the connection from the jack to the main volume pot as well though, since this is notorious for going bad on old metal-plate Fenders, although usually due to corrosion over time. It's often better to bypass it with a direct soldered wire connection from the jack to the volume pot, even though in theory this creates a ground loop.

Electro_Ham

Sound advice! Hopefully I'll have this thing quiet by tonight.

Electro_Ham

I think I'm going to throw in the towel guys. I've got 000 on pretty much most parts and 001 on only one or two. I've noticed that when I hold the plate with the jack plug on it, all the other plates don't buzz when touched. Unfortunately, I don't know what this means.
I sanded the back of all the plates, to make a good electrical contact because the chrome appeared to insulate. Now I get absolutely nothing, ie, the pickups are off, when the plate with the jack plug touches the copper foil shielding. It would appear I'm making things worse.
I'm thinking of handing it in to a tech in the hope that they can quickly work out the problem.
Pretty dismayed, I'm off to bed....But thanks for the help because we were definitely making progress.

ICBM

You've got a hot and a ground mixed up somewhere, so when the plate touches the shielding it shorts it out - the control cavity shielding is hot rather than ground. If you had this in the first place and haven't altered anything it's possible that it was combined with bad ground continuity so it wasn't showing up. That would also cause buzz when you touch something which is hot rather than ground.

The reason that you don't get a buzz when you touch both the jack plate and the other plates is because the ground is going via you. You don't really need to have the plates making contact to the copper foil if you've also got them linked with wires.

Rhoadhouse_Music

Have you considered you may have too many ground wires?

If you have connected everything with ground wires, plus the shielding, you may have a ground loop, hence the problems you're experiencing?

Also: have you made the mistake of shielding the jack socket hole?

You'd be surprised how many of my customers do this, but at least it's really remedied.

Then just twist the output wires around each other to guard against RFI...

Electro_Ham

Thanks again guys. You are giving me hope. I've definitely wired it as in the above schematic. The only difference between the '62 Jaguar and mine is that the shielding was only on the floors of the cavities and also on the back of the pickguard on the '62. I've shielded the whole cavity so that when the plates are on there is electrical contact made. I've also grounded every plate to the shielding with a wire. Total noob mistake. Do you think I could use electricians tape to stop contact between the plates and the shielding. That would be easier than trying to remove all the shielding (and conductive glue)?
Or should I just try to remove the copper foil where it was coming into contact with the plates? I also painted all cavities with shielding paint (before copper foiling)  which may have added to my troubles.

Rhoadhouse_Music

I always emphasise the often overlooked importance of shielding do my customers, but I think you may have over-egged this particular omelette!

Try removing the pot's, taping over the holes, then pokingthe pot's back through the tape as the simplest solution...

Don't beat yourself up: we all learn from our mistakes (apparently!)... :-S

ICBM

Don't worry about the paint, that's not the problem.

The easiest thing is to start from an earlier stage. First remove all the electrics. Cut back the foil cleanly to the tops of the cavity sides. Join every piece of tape to every other with a solder spot, and link all the cavities with wires soldered to the bottoms. Now you have one continuous guaranteed ground connection throughout the body. Connect the trem to this as well. Now the whole guitar - apart from the electrics plates and the pickups - is grounded. Check the continuity throughout with the meter.

Once you've done that, simply linking each plate to the shielding with one wire will make it all work. At that point it doesn't matter if the plates just touch the top of the foil or not.

Electro_Ham

I'd forgot so say that the problem still exists even when all plates are removed from the guitar and not touching any copper foil. I made a short video. Not sure if it will help though. The cavities have always been linked with short pieces of wire. I'm still getting 000 on the meter pretty much everywhere. Maybe 001 from the trem.

Electro_Ham

I forgot to say the amp is just at 2 out of 10. Other guitars would be silent at this level.

ICBM

Absolutely no question that there is a break in the ground continuity between the jack plate and the rest of the grounding. You just have to find why. It's so extreme that it sounds like the rest of the grounds are connected to the hot, rather than disconnected.

If allowing the jack plate to touch the shielding foil shorts out the guitar, could it be as simple as that you have connected the wire that goes to the shielding to the hot terminal on the jack instead of the ground?

Electro_Ham

ICBM said:

could it be as simple as that you have connected the wire that goes to the shielding to the hot terminal on the jack instead of the ground?

I think you've got it!!! I'm going to the dentist just now so I have to rush. Here's a couple of pics that might help diagnosis. Black wire is ground.
http://i236.photobucket.com/albums/ff212/larz55_2007/IMG_3728_zps0cvqk9v6.jpg
http://i236.photobucket.com/albums/ff212/larz55_2007/IMG_3722_zps6sm4hcz7.jpg