Star Grounding -- Insulating The Star?

[GregP]

The GuitarNuts' tutorial "Quieting the Beast" uses a ring terminal for it's 'star'. The following diagram indicates that it should be "insulated":

But unlike most of his other instructions, he deosn't really elaborate much. From what I gather, despite the fact that the diagram looks like all that metal is exposed, pretty much the entire star should be isolated from the electronics cavity.

Is that correct?

Or in other words, does he mean that once all those wires are soldered up, I should wrap'er up in electrical tape or other insulating material so that the 'star' is NOT touching the (shielded) cavity?

Greg

[lovekraft]

I think John's intent is to insulate the ground against accidental shorts - it shouldn't be isolated from the shield foil.

[Stalefish]

Yeah, I usually tape it up with the electrical tape.. Of course, you've got to have a wire running from the shield to star.. Like Lovekraft said, it's to prevent the star from coming into contact with something else..

[GregP]

There will be a wire running to star from the cavity shielding or from a pot (which should be in contact with the cavity, meaning the same circuit).

This is the part that threw me:

Insulate the signal return ring connector and any wires or control terminals that might touch the inside of the body when the pickguard is installed.  Remember, the body cavity shielding is now our "chassis" ground and we don't want any part of the circuit to touch it, not even those parts of the circuit that are at signal ground.

He seems to be saying that if the star is touching the chassis, it could also itself be a ground loop, no?

Greg

[lovekraft]

There will be a wire running to star from the cavity shielding or from a pot (which should be in contact with the cavity, meaning the same circuit).

OK, I missed that completely - it makes more sense to simply use the physical connection between the ring terminal and the shield, but if there's an explicit shield connection elsewhere, then the terminal will need to be insulated from the cavity shielding.

[GregP]

Hrm, I phrased what I said with too much certainty and authority. What I MEANT to say was:

The way he shows it all wired up, he uses a separate wire from the chassis (actually, a pot) to the star. But if it's better to NOT do it that way, I can just screw down the ring terminal and solder it to the cavity.

Is it because he's using that .33, 400V cap between a pot and the star? I don't have the concentration to wade through all the diagrams, but in that small version, it doesn't show all but the capacitor that's soldered to the star is then put onto a ring terminal which connects to a pot and hence the shielded chassis. It seems to me there was another one, too, but I really gotta sleep. <bleary eyes>

Greg

[lovekraft]

Is there a connection between the cavity shield and the pickguard shield, other than the pot you mention?

[Southpa]

I'm starting to use shrink wrap for insulating those bare spots. Just remember to slip it on the wire before soldering, .

[lovekraft]

Just remember to slip it on the wire before soldering...

Ooh, yeah, been there, done that...

[GregP]

Is there a connection between the cavity shield and the pickguard shield, other than the pot you mention?

←

Not in bed just yet. <laff> But this is my last post, then it's OFF TO BED!

In theory, yes. The copper foil insulating the cavity extends out from the cavities themselves, at which point in time they should contact the pickguard. The bridge and neck cavities are connected with a piece of copper foil, too, running under the pickguard. I can take pix tomorrow.

The Pacifica isn't exactly like a Strat or a Tele, though-- the pots aren't connected to the pickguard at all, though the switch is. The original (non-shielded, so I don't know why they bother) wiring has a ground wire connecting the switch to the neck pickup via a small terminal ring that goes around one of the switch's screws. Not sure what to make of that.

Greg

[GregP]

I finally have everything I need to start re-wiring my guitar (new iron, new solder, new wire, capacitors, heat-shrink tubing, etc....)

One final question:

It looks like the only ground connection between the cavity shield and the jack is the one that goes through the 400V, .33uf capacitor.

Can this be correct? I haven't a clue what a capacitor does. I just put them where they go. I just want to know that I'm still getting ground if the only 'path' to ground goes through the capacitor.

Greg

[lovekraft]

That's correct - the idea is to isolate the guitar from any large DC voltage at the amp input, keeping you safe from amp malfunctions.

[GregP]

Yes, that finally makes sense now that I'm thinking about it. The whole POINT is to have the resistor in-line so that if hot and ground are reversed (at the outlet or at your amp), there's a buffer between you and some lethal voltage. It really only works if it IS the only path to ground, I would think.

Cheers!

I know it's not much of an undertaking, but I'll take pics and post a mini-grounding tutorial here and also send it along to John.

Greg