buzz that I cant kill

[Granny Gremlin]

A final thought, Gibson shielded the back of their control cavity covers, but didn't ground this shielding or apply any additional shielding to the cavity itself? Why?!?

The back of the (front mounted) control plates were grounded by virtue of contact with pot casings.  Also they did  used to mount the circuits in a cavity-fitting metal can, in which case they made contact with the (rear mounted) control cavity cover, grounding it.  When they dropped the cans, I guess they just forgot about the whole thing, aside from the foil on the cover.   Not that it is needed with the humbuckers.  Some eras of EB series basses had these (not sure what period; may have been inconsistent):

[Dave W]

It might be worth checking continuity between all the strips of slug tape you used. Copper shielding tape is manufactured with a conductive adhesive, whereas this isn't necessary to keep slugs off your lettuce, so don't assume anything! I would solder a wee joint between each strip of copper tape if you don't get 100% emphatic electrical continuity across all sections of your shielding.

^^^ This. Slug tape adhesive isn't made to be conductive. You may have had enough direct contact to be conductive, but that could have changed over time. Worth checking.

[Alanko]

I realise that one part of my previous post didn't make much sense.

Shielding reduces electrostatic interference, whereas single coil pickups pick up electromagnetic interference. EMI can be reduced with dummy coils, twisted pairs and the like, whereas ESI can be reduced through shielding.

I would have thought that the Gibson shield posted above would be fairly ineffective as it is full of holes?

[slinkp]

Holes don't matter much apparently. Google "faraday cage".

[Granny Gremlin]

Yep.  You can do a room with chicken wire.

[Alanko]

Do the size of the holes not influence the wavelengths they intercept? I thought a Faraday cage was used for screening out electromagnetic interference, not electrostatic interference? Do they work for both?

My confusion here is making me wonder how well guitar manufacturers typically understand the shielding process? I've noticed MIM Fenders come with cavity shielding paint now. However my MIM P bass has nothing more than a thin strip of conductive tape on the back of the pickguard, so it isn't a complete shield by any means.

[Granny Gremlin]

The tape on the pickguard is not intended as a shield (with the humbucking P pup it's usually not required) - it is a ground plane (which may or may not have some shielding side-effects).

[wellREDman]

      badly done shielding was the answer, connected a bit of wire from the shielding to the plate in both the control cavity and output jack and a coat of conductive paint washed over the copper to ensure connection between all strips and the buzz is 99% gone .  I haven't done the same to the Pup cavity yet but I'm guessing that will be the last bit to bring it back to silent running

thanks for all the advice guys, as usual spot on

Red