Screening / Shielding a Rear Routed Strat

jaymenon

The control cavity: I have shielded comprehensively with good quality conductive graphite paint. 

The control cavity cover: is also shielded with copper foil and I’ve ensured electrical continuity..

Interestingly with the pickup selector switch in bridge position I get no buzz when I take my hands off the strings/bridge. 

However I get a little more buzz with the pickup selector in the middle position and a lot more buzz with the pickup selector in the neck position.

It’s almost as if the longer cables from the neck pickup are attracting electromagnetic interference...

Is there a simple solution please?

ICBM

jaymenon said:

It’s almost as if the longer cables from the neck pickup are attracting electromagnetic interference...

Is there a simple solution please?

It’s exactly that.

Replace the wiring to the pickups with shielded cable.

jaymenon

How do I do that please John?
They’re Kinmans - from Kinman I understand that the hookup cables are screened cables and so are immune to buzz. 

They suggest I shield the pickup cavity walls and floors if not already.
But If I paint the floors and walls of the pickup cavities, the 'roof' would still be open right?

ICBM

jaymenon said:

They’re Kinmans - from Kinman I understand that the hookup cables are screened cables and so are immune to buzz.

They should be - have you definitely connected the shields at the control end? (The bare wire.)

jaymenon said:

They suggest I shield the pickup cavity walls and floors if not already.
But If I paint the floors and walls of the pickup cavities, the 'roof' would still be open right?

Yes, but it will still make a difference. If the bridge pickup isn't buzzy it must be because it's closer to the control cavity shielding. (Remember that the shielding must be connected to the ground elsewhere too, or it won't work.)

*Some* buzz is inevitable with a passive guitar though - that's why the strings need to be grounded, so the player acts as a shield.

jaymenon

Thanks John

The pickups are two conductor
- ground to volume pot casing
- signal to selector switch

Re: connecting the pickup cavity shielding to ground, looks like I’ll need to connect a wire connecting each pickup cavity and the control cavity. since it’s rear routed with little channels connecting the pickup cavities to the control cavity. That’s  going to be really difficult... but I suppose a worthwhile challenge ...

ICBM

You don’t need an extra wire back to the control cavity - you can connect the shielding to the ground of each pickup with a short one under the pickup.

jaymenon

Hi John

For each pickup cavity
- One strip of foil affixed to floor
- Rest of floor and walls painted with graphite paint (overlapping onto foil for electrical continuity)
- A wire soldered to the foil strip and the volume pot

Now she’s dead silent - no buzz when I take my hands off the metal parts.

I was quite surprised since only the floors and walls of the pickup cavities are shielded - they are 'open sky' so to speak...

I thought you’d find that interesting!

So you were right - on rear routed instruments, graphite painting the pickup cavities really helps.

[Imgur](https://i.imgur.com/UdBYTRh.jpg)

ICBM

Neatly done - I haven't tried that combination of foil and paint, but I can see it has some advantages... not least that it's much easier to do than all foil! It should be a better shield than paint alone because the soldered wire will guarantee a better connection to a larger area, and the black probably looks better on the sides of the cavities than copper would too.