Rewiring a Gordon Smith

erratic_assassin

(This might be a bit of a ramble, but I'll try to highlight any actual questions when they occur.) 

I have an old ('99) Gordon-Smith Graduate, which I've owned since new but never quite loved, so I thought I'd give it a bit of an overhaul, and incidentally branch out into working on LP-type guitars - I've done several complete re-wires recently as part of an ongoing effort to work on my soldering skills, but they've all been on Strat types. 

The plan is to completely rewire the guitar as the pots are a bit scratchy and the current pickups aren't great. I have the replacement pickups lined up (a pair of Oil City Nightfighters), so I thought I'd do a bit of prep by watching a couple of YouTube videos, reading the appropriate sections in Gerry Hayes's "Complete Guitar Wiring", and opening the control cavity on the Graduate to inspect the current layout.... which is where things started going askew. 

First off, I reckon this particular guitar is a Friday afternoon special. I picked it up relatively cheap back in the day on account of some flaws in the finish, but when upgrading the tuners (relatively recently!) I noticed that they're placed somewhat lopsided, and having inspected the control cavity, the routing is rougher than a badger's bum-bum.  I reckon this guitar's going to be an absolute pig to work on when I get into it.

Secondly, the wiring layout is awful - a proper rat's nest. All of the reference materials I've looked at so far follow a recognisable pattern: four pots with capacitors linking the volume and tone controls for each pickups, with a ground wire going to the bridge, and a bare ground line connecting the pots. The GS follows none of this - there's no visible ground wire to the hardware or connecting the pots, and the capacitors are not used to link the pots.  I suspect I'll just have to spend a bit more time looking at the layout to work out what's going on, but I guess question one is: is there a reason why reference materials seem to favour that original layout with capacitors strung across pairs of pots?  

(Side note: I have a pair of Korean Epiphone LPs of similar vintage and opened them up to see if I could glean any insights from their wiring, since they both have coil splits. The wiring on those is also terrible, and no two of these guitars has the same wiring layout. ::sigh::) 

Question two would be: does nobody bother screening the control cavities in LPs because the position of the switch enforces the use of screened wiring, which makes all that fiddly business with copper tape redundant? 

And, on the subject of screened wiring, is there a good reason to choose one type over another? Is braided easier to work with than screened PVC, or vice versa? 

Lastly: how far into this do you think I'll get before I say "Sod it, I'm going to turn this over to a professional"?

ICBM

I think GS only worked on Fridays…

If you use shielded cable throughout, and the caps are on the tone pots so the volume and tones are linked with cables, there is no need to connect any of the pot casings other than with the cable shielding, and no real need to do any other shielding - although it can make a small difference if the exposed wiring cores aren’t kept as short as possible.

BillDL

You said:

".... having inspected the control cavity, the routing is rougher than a badger's bum-bum.  I reckon this guitar's going to be an absolute pig to work on when I get into it".

I assume by that you just mean that it will be awkward to fit the pots rather than soldering pots already down inside the cavity?  The reason I ask this is because it is a lot better and easier to wire up your pots on a template to hold them in the same positions as they will be in the control cavity, THEN drop them into the cavity.  Holes in the lid of a shoe box or drilled through a scrap piece of hardboard or thin plywood would serve the purpose to hold the pots with the shafts through the holes.  You place a piece of thin paper on top of the guitar, press around the holes for the pot shaft (and the switch if it's down at that end), then prod holes through the paper and write against the holes which pot each hole is for.  You then just flip the paper over so it represents the view into the cavity and transfer the holes to your rigid template and write on it which pot is which. If you already knew this, then just ignore the tip.

A couple of questions that might help us to offer some tips:

1. Is it the graduate model of the Les Paul shape (i.e. single cut) with the toggle switch on the upper bout or is it the double-cut version with the toggle switch down in front of the knobs?

2. What type of cables does the guitar currently have, i.e. multicore with external plastic insulation and inner braided screen or external metal braid with a single insulated core wire?

3. Can you get a good look at how large a diameter the channels for the cables are, i.e. how tight is the current wiring in the channels?

Unless you asked for custom wiring, the Oil City Nightfighter pickups have wire with the external braid screen (Gavitt wire) and a single core with push-back fabric inner insulation, so it would make sense to use the same wire from the toggle switch to the output jack socket.  It is good practice to buy the appropriate diameter heatshrink tubing to slide over the external braid wire where it passes through the control cavity in case it touches any of the pot lugs.  The outer diameter of this wire is around 1.8mm, so 2.4 starting diameter to 1.2mm shrunk diameter (i.e. 2.4mm 2:1 ratio) heatshrink tubing is fine for this job.

The reason I asked about the diameter of the channels through the wood for the cable runs is that external braid wire is often a bit thicker than plastic sheathed multicore cable, and two of those wires going from the control cavity to switch cavity plus a 3rd coming back through from it for the output socket needs a fairly large diameter channel.  If it's wired with multicore and the wires are snug through the channels three externally braided wires can be too tight.

The Les Paul Modern Wiring diagram you are probably looking at for a reference on Page 256 in the Gerry Hayes book shows a single separate wire soldered in a horseshoe to the backs of all of the pots as a continuous ground.

Having the capacitors wired between the volume and tone controls like the above is no different for the end result to having a plain wire linking the volume and tone pots and soldering the capacitor from the lug on the tone pot and to the back of the pot instead of bending over the pot lug and soldering it to the back of the pot as shown above.  There's several ways that the capacitor can be wired with the same results (see Page 136 of the Gerry Hayes book) BUT if you see it soldered to the middle output lug of the volume pot (see ES-335 diagram below), that is what they call Fifties or Vintage wiring and it DOES affect how the volume and tone pots work, where turning one affects the other. 

IF the wire from your bridge pickup is long enough, you should be able to use the outer braided screen to act as this continuous horseshoe shaped wire on its way to the bridge volume pot.  You will see this in the diagram for the Gibson ES-335 wiring on Page 251 of the book (ignore the capacitor wiring and go with the Les Paul diagram for that).  The wire that's shown as a coppery colour is the one I'm talking about below.  In the ES-335 diagram the wire from the output of the bridge volume pot to the switch has also been fed through the same heatshrink tubing on the aforesaid wire between the pots so that it's all neatly out of sight when looking into the F-Hole.  That part isn't necessary in a Les Paul because it's hidden, and the heatshrink on the braided wire between the pots isn't really necessary either as it's unlikely to come anywhere near the pot lugs.

So, looking at the back of the pots as they will be in the cavity while holding the guitar with the neck facing left, the volume pot for the bridge pickup will be closest to you.  If you take the bridge pickup wire first to the neck pickup volume pot furthest away from you and tack it to the back of the pot with a good blob of solder, then to the neck tone pot and do the same, then to the bridge tone pot and solder the braid to that, the wire will end up at the bridge volume pot where you can strip back the braid a short distance and solder the end of it to the pot while the inner insulated core continues to the input lug of the pot.  The external braid is already tinned, so it solders quite easily, and this way can be really neat, especially if you do nice shiny clean solder blobs to the outer edges of the pots.

With the pots in a template to hold them for soldering, it is wise to put a bit of a bend in the braided wire between the pots (i.e. solder to one pot, put a slight bend in the wire before soldering to the next pot) so that you have some slack on each of those wire lengths between the pots when positioning them into the cavity.

Also remember and leave enough spare wire from the switch to the output jack so you have a bit of slack to solder up the socket on the outside of the guitar.  It's quite a distance from the switch on a LP to the output jack and easy to cut that wire too short.

You asked about the benefits of Gavitt type wire with the external braid screen over plastic coated multicore cable.  For me it is threefold:

1. The braid can be used as your continuous grounding hops between pots, and it holds its shape better so you can lift the whole lot as one semi-flexible loom and transfer it easily to the cavity.

2. Where the braid is stripped back and soldered to the pot and the insulated inner core goes to the pot lug, if the wire is tugged it just tugs on the soldered braid rather than tugging the thin core wire of a multicore cable that is quite easily broken.

3. It's a lot easier to work with is less of a rat's nest of fine core wires.

SteveRobinson

The capacitors are on the push pull pots so that different values are used for full humbucker and split coil modes. 

Be aware that the pickup cavities may need enlarging as they will be cut just the right size for the proprietary pickups.

Funkfingers

My recollection of working on a four-pot G-S guitar is that the control cavity is nothing like as generous as, say, a Gibson or a Sire. It is necessary to ease all four pots (and any mode switches) out of the cavity in order to have any hope of getting a soldering iron tip anywhere near the contacts.

SteveRobinson said:

Be aware that the pickup cavities may need enlarging as they will be cut just the right size for the proprietary pickups.

This is also true of PRS. I once considered installing covered humbuckers in my early Nineties Custom (24). They would not fit. The corners of the pickup cavities were too rounded.

SteveRobinson

Funkfingers said:

My recollection of working on a four-pot G-S guitar is that the control cavity is nothing like as generous as, say, a Gibson or a Sire. 

I challenged John Smith on this and he said he liked to remove as little wood as possible to "preserve the tone"

Funkfingers

Perhaps, he should have taken that theory to its illogical extreme - controls mounted externally, like Les Paul's Paulveeizer

erratic_assassin

ICBM said:

I think GS only worked on Fridays…

I can't decide whether to be outraged on their behalf or simply nod and say "Fair".   This particular example is, ahem, quirky at best, but I also had a GS1 which predated my Graduate and was really well put together - just a simple design, executed well. I still regret selling it - try finding a solid mahogany guitar for £150 these days!

erratic_assassin

BillDL said:

... lots of useful stuff ...

In answer to your questions (numbering not the same):

1) I just get the vibe that this guitar is going to be troublesome. I had already planned to make a template and work on the pots externally. 
2) It's a Graduate 60 - single cut, selector switch positioned per a proper LP. 
3) Current wiring run from the switch appears to be one single-core screened wire direct to the jack, and one multicore? 
4) The Nightfighters have four-conductor wiring to accommodate splitting.
5) Wiring channel is approx. 7-8mm in diameter and comes out in the control cavity very close to the bridge volume pot. 

I suspect I might end up attempting to rewire one of my Epiphones first - changing the pickups was on my to-do-list anyway, so maybe it would make sense to use it as a practice run before taking a tilt at the GS. 

BillDL

Thanks @erratic_assassin   I jumped to a conclusion based on the photo of the pickup on the Oil City website that came up in a Google search, but should have read the full spec:

https://www.oilcitypickups.co.uk/product-page/copy-of-nightfighter-alnico-iv  (looks like an old or test page)

Had I seen  the other photo of the actual pickup I would have realised from the cable type even without seeing the description:

https://www.oilcitypickups.co.uk/product-page/originals-nightfighter-alnico-iv

If you are going to use the coil splitting feature I would offer a couple of tips.  Just remember that you're looking at the underside of the pots to the "out" position of push-pull pots are the bottom lugs of the switch as you are looking at them.  I've wired them wrongly in the past and had to undo it when I tested it, and I've had 2nd-hand guitars where previous owners have done the same but not tested it.  It's quite easy to get the lugs reversed when looking at your wiring template from the underside.  OK, so you can just switch the wiring around if you accidentally wired the pot switch in reverse, but it's a nuisance because it's quite fiddly.

I'm also mentioning push-pull pots for two reasons:

1. Gerry Hayes shows the push-pull switches with only wires to the lugs on one side of the switch (example on Page 320 of his book).  It is a better idea if you solder your wires to the lugs on both sides of the switch because it (a) makes it harder for the wire to be tugged out, and (b) if a contact on one side (switch internals or solder joint) is dodgy the wire is still connected to the other side.

2. A lot of tutorials show people tinning the lugs on pots and switches with solder in advance, then just heating the lug again to melt the solder, pushing the end of the wire into the melted solder in the hole, and removing the soldering iron for a nice neat job.  You can't do that if you are pushing a wire through the holes in two separate lugs because you can't heat the solder on them both at the same time.  The holes in the lugs of the switches on push-pull pots are pretty small, so it's best in this case to strip off enough insulation for a bare wire that will go through both holes and twist and tin it lightly, then apply solder to the lugs after the wires have been pushed through the holes in them.  

Glad you had already decided to use a template for soldering.  There was just something in your sentence that made me feel a bit uneasy and thought it would be wise to say so.

It's always hard to gather an idea of peoples' levels of technical knowledge and hands-on experience from a forum, so I apologise if any of what I said sounded simplistic.

Probably a good idea to do the Epiphone first for some experience and to iron out any issues you encounter.

erratic_assassin

Some time later....  

I did indeed use one of my Epiphones as a dry run. I did most of the work back in March, but finally got round to fixing the last ongoing problem as part of my Bank Holiday guitar work programme... and have even got around to putting some pictures on Flickr. 

Control cavity, before: https://flic.kr/p/2sf2QZk 

Wiring harness, assembled on external template: https://flic.kr/p/2sf1xfT

Note that the harness has coil splits on the tone pots rather than the volume, which I think is more usual? (Certainly that's how Gordon-Smith do things.) Also, the splits are partial (resistors on the push-pull pots) and there are treble-bleed assemblies on the volume controls, because I wanted to push the boat out and experiment a bit.   

Wiring harness installed in the (now-screened) cavity: https://flic.kr/p/2seZLnp

The finished guitar: https://flic.kr/p/2sf1XkT

The new harness was mostly okay but developed a fault where the neck volume control had no effect - the pickup still worked, the coil split on the volume pot worked, but the pickup was just always on full. Hence I've been back in today to clean up. I'm not sure what the fault was but I've removed the treble-bleed assembly from the neck volume (which was an unnecessary complication anyway), resoldered the pickup & switch connections, and all is good.

BillDL

That's a really nice and neat assembly, especially with the resistors discreetly soldered on the side of the push-pull pots.  Great job.

erratic_assassin

Cheers - I reckon it was pretty decent for a first attempt at working on an LP.  I started stripping and test-fitting the Gordon-Smith over the bank holiday weekend and my initial assessment that it's going to be an absolute pig to work on has been borne out... but that's probably another thread for another day.