Custom built Fender Jaguar USA. Shielding the cavities, and grounding the cover plates

Vintage Fender Jaguars are usually shielded, at least to some extent, by the installation of special brass plates within the body cavities. These are then directly linked to the metallic cover plates, and most of the other metal hardware components, via short fly-leads. This essentially means that the Jaguar is well shielded both above and below the plane of the pickups. Now, I’m no expert in electromagnetic radiation, and I can’t vouch for the shielding properties of the actual wood of the guitar body – but I was always under the impression that a proper, fully-shielding, “Farraday cage” effect, can only be achieved with proper shielding all around. Call me “Mr Belt and Braces”, or even “Herr Overengineering” – but I understand the basic principle of lining the internal cavities with conductive copper foil, and I’ll be doing it again here, in addition to the effect achieved by the usual shielding plates. This should theoretically guarantee a noise-free build, and what is more – the copper foil will cover up my necessary, (but ugly), “modifications” to the switching routs.

The body first needs to be stripped back of all installed components, (taking the neck off will also help), and then I can inspect the grounding plates – noting exactly where the linking leads and securing brads are placed. In the lower, diamond-shaped rout – the linking lead is soldered dead centre, and the short wire is stretched so that it slightly fouls the new, 4-way switch, when it’s dropped into place. It appears that the sprung switch mechanism is somewhat deeper than that of the usual up/down switches. I make a mental note to re-install all of the linking leads in locations where they will be well out of the way. Whilst the 4-way switch will fit into the cavity now – I can’t afford to have any connections potentially shorting out anywhere.

In the central, main pickup cavity – the plate has been, somewhat roughly, shoved into place and has deformed and trapped one of the linking wires, where it passes into the interlinking conduit. I’ll take a little bit more care when I re-install things, and I’ll try to flatten the plate out again. Elsewhere – the securing brads are released by de-soldering them, and removing as much of the surplus solder as I can, with a “solder-sucker” pump. The brads are worked loose with a screwdriver blade, and retrieved using some fine, long-nosed pliers. The out-lying plates are then separated from the leads which connect them directly to the main, central plate. The individual plates are a tight fit within the cavities – but they mostly fall out when the guitar body is inverted. Those which remain stubbornly in place, can be worked loose by trying to work a fine blade around the edge, and underneath.

Fender Jaguar grounding plates, and linking wires

Having removed all of the grounding components – I clean them up as best I can, check the wires for wear, and straighten out the plates where necessary, so that they’ll re-install flat. I remove as much of the surplus solder as I can, and check the triangular brads so that there’s at least one clean sharp corner on each. These will have to cut back into the wood of the body, if I can’t find the exact, original, point of insertion.

With the plates removed, I can get a fuller picture of the condition and provenance of the body. Original labels from the manufacturing process are evident underneath the brass grounding plates, and I’ll aim to remove and preserve these as effectively as possible. Normally, these labels come off fairly easily – but if they’re stubbornly holding on, a little naptha can soften the glue enough to allow them to be peeled away. I’ll put them back in-situ, once the cavities have been copper lined. The labels aren’t exactly “historic” or of any other great import – they’re mostly left over from Fender’s automatic processing and warehousing inventories. However – they do give me a definitive Fender parts number for the body (771-1787-609) and an exact, apparent, production date. The only other process mark is a blue, painted “P” in the main control cavity.

In de-soldering the brass plates – the lacquer underneath, where the tip of the soldering iron has been placed, has slightly melted – revealing a metallic gold undercoat layer. This is useful knowledge. “Candy Apple Red” was originally a custom colour offered by Fender, and is achieved by spraying a translucent red paint over a metallic undercoat. That undercoat was, in early examples, usually a gold paint – (perhaps, most likely “Shoreline Gold”, or similar). However, there appear to be examples where a similar effect has apparently been achieved using a metallic silver undercoat paint, (Inca Silver?). The difference is subtle – but noticeable. (In my opinion the warmth of gold underneath the red is much warmer and more, “toffee-apple like”. The silver, somehow, seems to give the red a little less depth). It’s also quite possible that different undercoats may lead to differences in the gradual toning, due to age, that most nitro paint colours undergo, when exposed to sunlight. (For a little while – Fender apparently offered an “aged” translucent red paint colour on some of their “Johnny Marr” Jaguars. This may have been achieved by using an “antique gold” underneath a thin, translucent red, topcoat).

With translucent paint colours – the undercoat is everything.

Lining the body routs with conductive copper foil

The body routs are then lined with overlapping strips of copper foil. The foil has a conductive adhesive, and the foil is well burnished down with an agate burnishing tool, to ensure optimal contact. A few strategically placed tabs are left to help provide points of contact between the lining foil, and foil which will, in turn, be placed on the back of the scratchplate. (Vintage Jaguars used to have a, roughly rectangular shaped, aluminum plate over and around the pickup area. This would be held in place under the scratchplate, with a couple of the pickguard screws). Usually, the individual cavities would be joined, and made contiguous, by laying wires underneath the foil and through the interlinking conduits. However – this exact same effect is achieved via the cloth-covered linking wires which physically join the re-installed brass plates. Since the brass plates and the copper foil will ultimately be in direct contact – it is possible therefore to bring all of these shielding elements together, and provide a single, continuous, ground.

Once the copper foil has been burnished down, I replace the original production stickers in their original positions. Where the original glue has been stripped away – I use double-sided sticky tape.

Re-installing the brass shielding plates

At the switch rout – there’s evidence of some “sponginess” to the wood where I’ve chiselled out a small step, to allow the switch to sit astride the opening. It looks like the grain of the wood may have been much softer here, and it’s possible that the nearby screwhole taps down into a void. I press in, and compact, plenty of two-part filler, allow the area to dry fully, and then easily carve back the shape I require. Copper foil can then be applied over the modifications and repair – I leave a couple of tabs out to the plate screwholes, although these aren’t specifically required. It just tidies up the edges, and will ensure there’s no chance of the paint finish lifting off where it’s been cut through.

Once all of the copper foil is in place, and it’s been burnished down properly, I can re-install the brass grounding plates. The central plate is installed last, and the connecting wires pushed through into the various outlying cavities. The original securing brads are pushed back into place, (ideally finding their original placements. It pays to take photographs as you go). The brads are fixed in place with small dollops of solder and, rather than attach the linking fly-leads anywhere else, it seems to make sense to place the connections in the corners of the cavities – using the same solder as that used to secure the brads. Because the wires are pushed into the corners of the cavities – it will be far easier to keep them away from any of the switches, and it also allows the direct solder connection to be extended to the copper foil on the sides of the cavities.

Routeing and securing the tremolo plate ground wire

A single connecting wire extends from the main control cavity, (where it’s secured and soldered in against the closest brad), through to the tremolo cavity. It’s a cloth covered wire, and the end has been stripped back and the individual core wires separated and splayed out. Having applied a small copper tab, made out of self-adhesive copper foil, around a suitable tremolo screw hole and down over the edge of the tremolo cavity – I twist the very ends of the core wires together, and insert them down the screw hole. Keeping the visible portion of core wire spread out, I then sandwich this exposed core under another tab. This allows me to provide a good contact point, whilst simultaneously securing the wire in place.

Once the ground plates are secure, and have been soldered-in, continuity is checked and confirmed between all shielding surfaces, and throughout all of the control cavities.

Fashioning some grounding fly leads

Having provided a couple of strategically placed, conductive tabs, overlapping onto the face of the body – it should, normally, be possible to complete the shielded compartment by simply installing the metallic cover plates in direct contact. Fender usually used short fly-leads to accomplish the same task – where there’s normally no copper foil to achieve direct continity between the brass grounding plates and the chrome cover plates. Despite the fact that I’d probably be able to get a decent enough result with my copper foil overlaps – I do appreciate the certainty that a well-placed grounding wire can provide, and so I decide to pursue that route here, in addition to the continuity offered by the foil. Over-engineering again? – almost certainly – but it somehow seems more authentic this way.

I knock up a couple of short grounding leads using some cloth covered, push-back wire, and a couple of small screw lugs. The screw lugs will firmly attach to the underside of two of the control plates – betwen the plates and the switch housings. Since the main control cavity has no suitable location to install a lug this way, I’ll use a stripped and fanned-out grounding wire approach there – similar to the grounding wire previously installed at the tremolo cavity.

Locating the ground fly-leads at the two main switch compartments

Once the ground wires have been assembled and soldered – I use a short length of shrink-tubing to protect the solder joints, and to eliminate any chance of a stray short-circuit at any of the switches. The wires are then soldered in at the corners of the two switch compartments. I use the same corner locations which already bring together the ground plate continuity wires, the brass plates, the securing brads, and the sides of the copper-lined compartments. The fly-leads should be just long enough to allow for easy attachment.

Main control cavity grounding lead

At the main control cavity, a short length of cloth-covered wire is stripped back and soldered into the corner. The stray ends are pushed into the nearby screw hole, and then the fanned out wires, which run over the copper-foiled edge of the control compartment, are secured in place with another tab of copper foil. Again – this “sandwich” holds the wire securely in place, and provides the best physical and adhesive continuity. Once the ground fly-wires are in place – continuity is checked and confirmed throughout.

Applying conductive foil to the back of the scratchplate

I can now begin to re-install all of the control plates in turn – checking shielding and ground continuity as I go. First, I apply an area of copper foil to the back of the scratchplate – roughly coresponding to the area around the pickups, and extending out, so that it comes into contact with the tabs I’ve placed around some of the securing screw holes. The scratchplate can now be screwed down into place.

Insulating the switch cavity

However – just before I go about installing the 10 scratchplate screws – it occurs to me that the fit of the horizontal 4-way switch plate, within the actual scratchplate, results in the telegraphing of the copper foil and red paint, below. On checking the fit of the switch within the cavity – I’m also a little concerned that there may be minimal clearance left at the bottom of the cavity. It’s just possible that this may, in some circumstances, result in an accidental short. A few lengths of black electrical insulation tape, applied around the edge of the cavity and down inside, following the path of the switch terminals, should eliminate any possibilities of an accidental short circuit, and should also provide a clean black shadowline around the control plate, once it’s dropped into the scratchplate cutout.

With all that cleared up – the scratchplate is finally screwed into place.

Original Fender tremolo collet (left), and Staytrem upgrade collet (right)

Next to be fitted, is the tremolo plate. However – I have an upgraded Staytrem collet to install first. This improves on the usual, “floppy” tremolo arm, and has a nylon sleeve within the mechanism to keep the tremolo arm precisely, “wherever you last left it”. Staytrem replacements are available for both Metric and Imperial tremolo units, and it’s important to make sure you obtain and use the correct one.

The original collet is unscrewed from the tremolo plate. This takes a good wrench with a socket drive – so it’s wise to clamp the plate firmly, and safely, between some soft timber “dogs” on a bench vise. This avoids the risk of scratching or damaging the chrome plate. Once the new unit has been firmly torqued back in, (with a little bit of Loctite to secure the joint), the unit can be “engaged” by sliding the toggle-switch down underneath the loose, hinged plate. Tightening up the spring tension screw then pulls the hinge plate down – just enough to stop the plate rattling and flapping about. The correct operating tension will be properly set once the guitar is strung and tuned. I’ll fit the tremolo arm then, also.

Fender USA Original 60’s jaguar – control plates installed

The tremolo plate is installed with it’s six securing screws. The ground fly-leads at the switch compartments are connected to their respective plates by fitting the lugs – each around one of the switch screws, between the switch mechanism and the control plate. All three control plates can then be re-attached in their pre-determined positions. Once again, continuity is assessed and confirmed using a multimeter. Now – all the metal hardware components on the body, (except the strap pegs and, as yet, the bridge thimbles), are connected. They all form part of the continuous “ground”. Once a connection has eventually been made to the jack ground, (and hence, beyond, to the amplifier ground), the control circuit should operate properly, and electrical interference should be all-but eliminated.

I do still need to look at grounding the bridge, (and will also have to ensure any other additional metal hardware – the pickup claws for example – are also wired in correctly). As regards the bridge – It may well prove that the installation of strings is enough to form an effective, conductive connection between the tremolo and bridge units – although on my White “62” Jag, I grounded the bridge there directly, via one of the bridge thimbles. I’ll look at the issue again once I deal with installing the bridge. I don’t actually use a Fender mute unit much, in practical terms, but I have a replacement unit to install on this build, (I stole the original for my “62” Jag and eventually got round to sourcing a replacement), and I do always prefer the overall look of the Jaguar, with a mute unit and bridge cover in place. With all that extra metal around the bridge area, (and bearing in mind the corresponding risk of ungrounded metal hardware), I may be able to work out a suitable, but elegant way, of adding a hidden connection.

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