Too simple a wiring question for this forum...

[c. winn]

...so before I start, I'll send a big thanks to everyone  the forum - I'm a big fan of the Frets website (thanks Frank!) so I thought I'd ask for your help here.

This is a simple wiring project on a lap steel guitar.  SIngle pickup, volume control & output.

The body I am working with is from a Morrell "Little" Roy Wiggins lap steel:

This is a pic I found online of the finished bridge.  You can see the p/up route from the minimal pickguard.

What I am wondering is how I should ground this guitar?  Everything I read says that I should ground the electronics to the bridge, but everything on this guitar is top routed - I can't run wires to the bridge without extra routing & an oversized pickguard.

So this is what I'm working with:

And this is what I'd like to have in place:

WIthout routing a channel to the bridge assembly, where would I put a ground?

My high-school science teacher father-in-law (who is brilliant, in my opinion) and my itinerant tinkerer brother-in-law (likewise, brilliant) suggested a screw placed at the base of the cavity, and ground to that.  Sounds good, but I'm worried about the copper tape (from StewMac:  http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Shieldin... ).

Any advice you all would have is greatly appreciated.  I'm a 100% acoustic guy.......but all of a sudden, I'm strapping up an 8 string lap steel.  I'm really looking forward to getting this going......

Thanks again - 

Chad

[Mac Walker]

If I understand what you're trying to accomplish correctly, drill a hole starting underneath the bridge (it would be covered by the bridge and not be visible with the bridge installed) to the closest point you can reach inside the control cavity. Target half of the depth of the cavity for your bit to come out.

So you would drill at a 45 degree (or so) angle, and would not need to route for a larger cavity.....

[Mike Kolb]

Yeah... I like Mac's idea better than mine... "simpler is better". If you can start the hole at the upper right corner of the bridge footprint, and aim for the bottom of the cavity... you're in business.

[Mike Kolb]

There's some real electronic wizards here, so I'll defer to their better judgment... However, if this were sitting on the workbench in front of me, and a bridge wire were 100% required (not sure that's the case), I'd be sorely tempted to take a long skinny drill bit and, starting at the butt-end and adjacent the last bridge screw on the treble side, (midway up the side) aim directly for the area of cavity nearest the starting point. Make sure the path of the drill intersects the last screw hole. Then run a bare wire down the screw hole, work it into the cavity, and plug the hole with a nice little matching plug of wood. If all goes well, the screw will connect to the wire, which connects to the copper shield, and you're in business. But there must be other ways to skin this cat!

[c. winn]

Just wanted to make clear - I'm actually looking for alternatives to a bridge ground.

Were I to ground to the bridge, I'd probably just route a channel to the bridge, ground the wires, and hide them with a slightly larger pickguard than what I had in mind.

I'm interested in alternatives to a bridge ground. I'd like to leave the routed area as it is, and I'd like to know if anyone has an alternative to routing to the bridge.

The routed area is extremely narrow - I do not intend to drill a hole between the route & the bridge.

Thanks for your help -
Chad

[Russell Vance]

Just drill the angled hole from under the bridge to the cavity (1/16 or 3/16 long bit will do it) and use a multi-strand bare wire that will flatten out under the bridge and solder all your earth wires to a common point - the back of the pot and then to the earth tab on the output jack.
If your looking for an alternative to a bridge ground you're plum out of luck, with the pickup you have you need a ground - just do it as it's done and get on with it. If you can't drill a hole take it to someone who can. That way you do not need to rout a channel and change the pick-guard configuration (which is al ot more bother than drilling one small hole).
Rusty.

[Tom Krebs]

You'll end up with a nasty hum without a string ground to the bridge.

I use and extra long 'aircraft bit' to get a good angle. I would ground the strings/bridge to the back of the pot, then to the copper, and install copper on the back of the pickguard making sure it all connects together well.

[Tom Krebs]

One more thing is that your copper should have a small lip that runs up over the edge of your routing onto the face of the guitar to make contact with the sheilding on your guard. See photos in your StewMac link. That way when you install the guard you have a closed box of shielding. Copper seams in the cavity should be soldered and a ground wire attached via a wire/screw/soldered as your science friend suggested.

[Joshua Levin-Epstein]

An alternative to drilling would be to run some copper tape from the pick up cavity to under the bridge. A piece of copper sheeting would be better (the tape is fragile) and has been done before. This is the way the Jazz Bass was originally grounded. The StewMac tape accomplishes continuity with the adhesive, so you could just make contact with the cavity shield. Or you could solder the various pieces of foil (like we did in the old days).

But Fender changed to a hole drilled from under the bridge to the cavity quite quickly. So maybe that is a better to ground the strings.

Joshua

Joshua

[Rob Mercure]

The only alternative to grounding the bridge assembly is to use balanced low impedance pickups - some studio instruments are designed this way - but other wise, like all others have stated, you're going to have a hum problem otherwise. Perhaps I read wrong but somewhere you seem to asking about how to connect a ground to the copper tape. I've not worked with SM's but most tape is a thin copper layer with adhesive backing and you can simply clean a spot with steel wool and solder a wire to it. Generally I don't trust mechanical connections for grounding so anywhere you can solder go for it!

Rob

[Mac Walker]

Without a bridge ground your strings act like an antenna, amplifiying noise (RF interference, static, etc.) that will then be transmitted to your pickup (ESPECIALLY single coils). In one situation it might sound fine (in your shop for example), but then, get it on stage with a bunch of lights and other electrons flying around, and it can literally ruin a gig.

The only downside I'm aware of to grounding a bridge is that there would be a shock risk IF you're playing through equipment that isn't grounded and/or phased properly. For example a PA system with the neutral and hot reversed, and a tube amp with neutral and ground connected correctly. Then you would have 120VAC between your guitar strings and the microphone screen. There have been confirmed deaths from this kind of thing, but this was the early days of live sound.

Anyway I can't understand your aversion to grounding the bridge other than the above reason?

[Rob Mercure]

Mac,

While this used to be a great problem - I well remember having singed lips from a PA mic differently grounded than the instrument - the problem can be lessened by using a capacitor between the bridge ground and cord gound. something around 0.01 microFarad will serve to short out hum while having sufficient impedance to turn a shock into a tingle (if you're old enough you probably remember line connected series heater string tube radios such as the "All American Five" and TVs). I haven't had to use this trick in years as most buildings are finally up to code - the issue more comes from extension cords where some idiot has removed the grounding prong from the plug.

Rob

[Mac Walker]

Yeah, wet lips and sweaty hands are a contributing factor as well, as they increase the conductive path through a person's body. In my earlier years I would check the wiring before playing by placing my left hand thumb lightly on the crimped portion of the string at the tuner post and "sweep" my hand lightly in front of the mic screen. I would also check the other guitarist's setup using his guitar and mic this way. Ah, the good old days.....