Cavity shielding problems

[Mazdziosz]

Hey
I'll quickly start with the problem I got.
I tried to shield my guitar cavity from the unwanted noise, soo I took the aluminium tape and I filled the whole cavity with it. Everything seemed to look fine, but when I connected it to my TonePort GX instead of getting it more quiet, it just got louder.
Ground is wired to the volume pot but from this SCHEME I can see that the ground is suppose to be wired to the switch selector.
I noticed also when I touch metal parts on my guitar it goes a bit silent, but still it hums more than before the cavity was shielded. My backplate also has the aluminium tape. Everything was checked with multimeter. Will it matter if I solder the ground to the pickup selector instead of volume pot ?
Here's the picture of what I've already done.
Picture
My guitar is Washburn WI14.

 

[Omega_Void]

... Will it matter if I solder the ground to the pickup selector instead of volume pot ?

It's preferable.

Don't coil up the excess wire lengths either -- loops make great antennae for picking up noise.

... I took the aluminium tape and I filled the whole cavity with it. Everything seemed to look fine, but when I connected it to my TonePort GX instead of getting it more quiet, it just got louder.

One problem with aluminium is that it forms an oxide layer very quickly on its surface. Aluminium oxide does not conduct, so it's likely that the aluminium is not all connected electrically.

The oxide layer is very fragile and easily scrapes off, but re-forms almost instantly. It also makes ally extremely difficult to solder to.

Any electrical conductor not connected to a voltage source is "floating", and will assume whatever voltage it is influenced to by external noise sources. This voltage then couples via stray capacitance to the circuitry.

... I noticed also when I touch metal parts on my guitar it goes a bit silent...

This is normal, since you are electrically conductive. If your voltage is left "floating" it will be modulated by any external noise, and couple to the guitar circuit. The metal parts on the guitar are connected to the system voltage reference (ground), so when you touch them your voltage is dragged to the same voltage, and you are no longer a source of noise.

Try opening the cavity and touching stuff inside. When you touch the ground wiring the hum will be reduced. It should also be reduced when you touch the aluminium foil -- if this doesn't happen you know the foil isn't grounded.

Best solution is to do it again using copper -- it's nearly twice as conductive as aluminium and you can solder it easily, so you can maintain conductivity across the joins.