If you’ve been following this, (relatively lengthy and meandering), project so far – you’ve clearly got some stamina. You’ll also know, by now, that I’m intending to install this little Fuzz circuit board into a reliced Stratocaster build – using a dedicated push/pull control pot in the second tone position. I’ve now got everything I need to complete the electronic installation – pickups, switch and pot controls, and a functioning Fuzz – but first, I need to make a few changes – to correct a few small issues which have been thrown up, on the way here…
Firstly – I’ve relined the base of the “Clapton Rout” cutout – where the Fuzz circuit board will sit, under the scratchplate. Previously – the “loop” side of some thick Velcro, acted as a sort of restraining cushion – and was intended to help stop the board from rattling about. However – it’s thickness, meant that the tall capacitors on the board made it a bit of a tight fit, once the scratchplate was screwed down. Also – the cavity had originally been lined with copper foil, and there was always a remote possibility that the sharp solder joints on the base of the board might have been pushed through the Velcro padding – shorting-out on the grounded shielding foil. Now – I’ve stripped out the Velcro and copper foil from the base, and replaced it with a much thinner sheet of polythene packaging foam. It should do roughly the same job – at about a quarter of the thickness.
Secondly – one of the screws for the scratchplate doesn’t quite hit the “meat” of the body – down by the main control rout. I strip out the copper foil lining, adjacent to the screw position, and make up a half-oval piece out of scrap wood, which is as long as the main cavity is deep. This is then glued into the cavity wall with Gorilla glue, with a temporary clamp left overnight to keep the block in position. Once the glue is dry – I cover the new wood fillet with some scraps of copper foil, and tap the reinforced screw hole. The loose screw now has plenty of new wood to bite into, and should be totally secure once again.
To get the electronics working as I want them – there are two main elements which I need to bring together. The guitar tone circuit itself, and the separate FX board with it’s concealed 9V battery power supply. The main difficulties will lie in managing the resulting tangle of wires – keeping the wire runs economical in length and organised, while all the time ensuring that the final circuit remains accessible for troubleshooting and maintenance, whenever the scratchplate is removed.
There are also a couple of “unconventional” or adapted components to consider – which offer functionalities that are not normally required in a standard guitar circuit. While I’ll still be using a standard, sprung, 5-way lever switch – (this one by Oak Grigsby) – the usual jack socket needs to be replaced with a stereo variant. The additional ground terminal on a stereo socket can be used so that inserting a jack plug into the socket, both hooks-up the tone circuit output and, simultaneously, effects a simple power on/off “switch” for the FX board’s battery.
Also – the “one knob” Fuzz circuit will be controlled by a push/pull rotary pot, (a 500k, audio taper, short-shaft, push/pull control – by CTS) – this to be installed in the usual, second tone position, mounted on the Stratocaster scratchplate. The dedicated DPDT, push/pull, off/on switch will provide a “true bypass” function, (where the guitar signal will pass, unaffected, to the output jack in the normal way), and will activate the Fuzz circuit when the control knob is lifted. The rotary pot will then control the basic level of the effect. The control pot will be connected between the output of the tone circuit, (which needs to be modified to operate with just one tone control, instead of the usual two), and the output jack socket.
I’m using a circuit diagram obtained from the impressive, and ever useful, online, Seymour Duncan resource. The modified, single volume control / single tone control / 5-way switching schematic, simply routes the “hot” signal from the three pickups – via the “control” terminals of the switch – to a single output wire. The pickups can be soloed or combined in the usual manner, by manipulating the switch – and the signal is routed through the tone and volume controls, and then on to the output jack. (The push/pull FX pot will eventually be inserted just before the output jack).
In terms of putting all of the electronics together – it makes sense to build the scratchplate mounted tone circuit first – including the necessary linking wires for the push/pull pot. Since the solder connections for the push/pull pot are tight and fiddly, and since the wiring will become considerably more complicated at that stage – linking the FX pot and mounting it to the plate will be much easier, if that exercise is treated as a separate task, all of it’s own.
So – for the tone circuit – the scratchplate is first paired and backed, with an aluminium shield plate, (by Charles Guitars). This is held in place by the control elements, as they are attached – and all of the various perforations are specifically sized and positioned, for use with a “vintage style” Stratocaster scratchplate. The Oak Grigsby switch is positioned first – with it’s “spring side” set facing away from a pair of 250K, CTS pots in the “volume” and “first tone” control positions. These control pots are “SSS Premium”, (by Six String Supplies). They feature a “vintage” audio taper, and are built to within 8% tolerance. I angle the terminals of the pots into the space between the controls and the main switch. This will help to keep the wire runs short and uncongested – and should also offer slightly more space to work in, than if the pots were installed directly “facing each other”.
With the pots positioned correctly – the retaining nuts on the face of the scratchplate are given a drop of blue LocTite, as they’re tightened up. Serrated washers on the underside of the pot connections also, simultaneously, create a conductive grounding connection with the shielding plate. There’s therefore no real need to install a “running” ground wire here, between the pots and switches. They should stay locked in place, and in constant contact with the shielding plate. A single, grounded connection to the back of one of the pots, (or to the shield itself), will be enough to ground all of the scratchplate’s mounted controls.
The basic tone circuit is completed using white cloth “push back” wire, and white shrink tubing at the “straight-on” joints. I find that using shrink tubing helps me to focus on the layout and construction of the circuit a little more than usual – and it will also serve to insulate and protect the solder joints. It should also support and maintain those particular direct connections – in some cases, even if the joints are stressed or otherwise disturbed over time, (due, perhaps, to pressure from other wires, as the scratchplate is tightened down). It’s always useful, therefore, to check the basic connectivity as you go, with a multimeter. Once the point-to-point connectivity of each wire is checked and confirmed – the joints can be covered with the shrink tubing. This will also help with fault-finding later on. When things begin to get complicated – it will be good to know that, at least the basics are working as they should.
The tone capacitor, (on the left in the image above – mounted over the single tone control), is a 0.0473µF Cornell Dubillier 225P “Orange Drop”. It’s been positioned with a length of insulating tube over one leg, (attached to the middle “wiper” terminal of the control pot), to prevent it from shorting – and is awaiting a dollop of solder to ground the other leg against the back of the pot. At the volume pot – a ready-made “treble bleed” network is added to the basic Seymour Duncan schematic. This is connected across the “input” and “wiper” terminals, and consists of a 0.001uF “Orange Drop” capacitor, and a 150k resistor. The network will help to preserve the treble frequencies as the volume is rolled off, and both legs are insulated to prevent shorts to ground, on the back of the volume pot. (It’s often difficult to completely cover the treble bleed cap legs – especially where the resistor is soldered across them. If the cap is pushed back, perhaps due to pressure from other wires around it – a troublesome, intermittent short can sometimes occur, with one, or other, of the exposed joints coming into contact with the grounded back of the volume pot . I often choose to route grounding wires, or other signal wires, underneath. Anything to keep the cap lifted slightly away from the body. If in doubt – provide a physical block – eg. a piece of insulating plastic film etc., or, alternatively, position the cap well away to one side).
With most of the basic tone circuit now in place – I can fit the pickups to the scratchplate. I’m using a set of Fender “Pure Vintage ’65 Stratocaster” pickups. and will be replacing the stock covers with some “Vintage White” replacements, which have been lightly aged. The pickups come supplied with all the required fixings, but I dip the new screw heads in Ferric Chloride for a few seconds first – to take away some of the bright, polished, nickel coating.
With the pickups fitted to the scratchplate – the plate is inverted, and the signal wires routed down towards the controls. I find it useful to pair off the “hot” and “ground” wires into different bunches – inserting lengths of shrink tubing along the way, to help keep things tidy and “on track”. The white “hot” wires are looped over the back of the volume pot, (where they’re ideal for shimming that treble bleed out of the way), and are then looped “the long way round” to the terminals on the main switch. This takes up much of the excess length of each of the “hot” wires – and they usually then require only minimal trimming. (It’s usually adviseable to keep an eye on the routing, or to temporarily label each wire – since they look exactly the same, and they’re all usually the same length).
The pickup “hot” wires are soldered to their respective terminals at the switch – with the trailing wires curved gently, around and over the control pots – so the wires don’t kink. The three black “ground” wires are bunched and trimmed in length, so they can be soldered together – direct to the back of the volume pot. The remaining loose white wire in the image above, is the signal output wire, which will eventually connect-in to the push/pull FX control pot.
The scratchplate and mounted components are now set aside for a while. A black cloth ground wire is prepared – long enough to extend through the conduit, and out into the tremolo spring cavity, at the back of the guitar. Another similar fly lead is similarly prepared, (which will eventually ground on the back of the volume pot – thereby connecting the grounded elements on the scratchplate, with those on the guitar body). These two ground wires are soldered together, with a screw lug, and the lug pinned to the wall of the control cavity at a convenient point – away from the pots and switches. (I choose the flat wall at the “big end” of the cavity). Some shrink tubing is used to insulate the solder joint, and to help keep the wires paired, and out of the way.
At the back of the guitar – the ground wire is routed around the side of the cavity – where it will be out of the way of the tremolo springs. A little slack is left to allow for the tremolo claw to be adjusted – and the end of the wire is then trimmed to length, and soldered to the spring claw. This grounds the claw, as well as the tremolo springs, block and plate – all by means of direct, metal-to-metal contact – via the ground lead, to the main “star” point. I prepare a loop of thin, double-sided Velcro tape, and staple it securely into the channel I’ve previously cut – where the battery for the FX board will sit. A battery connecting cap is set in place – with it’s red and black leads running back through the conduit, and into the main control cavity. The cap will be connected to a 9V battery – with the cell secured, in place, between the two tremolo springs, with the Velcro strap. However – I want to complete the electronics installation, and then test it for the pickups only at first, (with the FX board left unpowered). So – once the effectiveness of the velcro strap has been confirmed – the battery is temporarily removed.
The jack socket plate is now removed from the guitar, and lead wires are soldered to the terminals. Once again – all of the joints are insulated and protected with shrink tubing – continuity having first been double-checked and confirmed, with a multimeter. The leads are cut on the generous side – to allow for the independent withdrawal and removal of the jack socket – (should it ever be required) – without the need to also remove the scratchplate.
A length of thin, black plastic covered wire – similar to the one on the battery snap – is connected to the secondary “middle” connector. A black, cloth-covered ground wire is connected to the usual, negative, “sleeve” terminal, and a similar white wire is connected to the main, positive, “tip” terminal. With the wires connected and tested – they’re fed through the small conduit leading into the main control cavity, and the jack plate is seated back onto the body, and secured with it’s two screws.
Inside the main control cavity – the thin, black, plastic covered wire is connected to the similar, black wire from the battery snap, which has been fed through the conduit from the rear compartment. The ends of the wires are simply twisted together, and secured with a drop of solder. The exposed connection is then insulated with a piece of shrink tubing. That’s the ground wire from the 9V battery now connected to the “switch” on the jack socket, and the FX circuit will only draw current from the battery, when there’s a jack plug in the socket, to complete the power circuit. These wires can now be tucked out of the way, at the bottom of the control cavity.
There are now four unconnected wires left emerging from the control cavity… The “hot” red wire from the 9V battery, a white “signal” and a black” ground” – both leading through to the output jack socket, and another black “ground” wire, which will eventually connect to the back of the volume pot. It’s a good idea to constantly “keep an eye” on where these four wires are, at any one time. From here on in – the process becomes a little bit more complicated…
Complicated – because the FX circuit board and it’s dedicated control pot, now have to be connected in with the tone circuit. That’s another eight wires added to the equation. Because of the type, and size of the terminals on this particular push/pull pot – it’s much easier to work on things, at the moment, with the pot still off the scratchplate. Therefore – it’s essential to check that all of the connecting wires are trimmed to the correct length, (bearing in mind that there has to be a little slack to allow the scratchplate to lift and rotate), and to have an idea of how things will be routed, in each case.
Before any of the other other connections are made at the push/pull pot – a jumper wire has to be laid between the “common” terminals, (#’s 2 and 4). This means that the pot will be “off” when the control knob is fully depressed, and turned “on” by drawing it up and away from the scratchplate. I use a piece of red, cloth-covered wire, and route the jumper under and around the terminal block – so as not to block access to the rest of the connections. Then – the input and output “send” wires, between the FX board and the control pot, are connected to the #’s 1 and 3 terminals, on the block. (FX Input “IN” to 1, and FX output “OU” to 3). Again – the “send” wires need to be long enough to reach the control pot, and of sufficient length to allow for periodic removal of the scratchplate to it’s “maintenance” position, when the pot is eventually mounted in position, on the plate.
Next – the red “power in” wire for the FX board, is spliced to the loose red wire which comes from the battery snap in the rear compartment. The splice is insulated with shrink tubing – and the pair of wires stashed away at the bottom of the control compartment, as before. With the terminals now beginning to fill up – it’s important to keep organised, and on top of things. Try not to let loose wires begin to cross over everywhere – confusing things visually…
Finally – the white “hot” output lead from the jack socket, is soldered to the “C2” (signal out) control terminal on the push/pull pot, and the three, coloured, rotary control wires are attached to their (correct) terminals on the control pot – just as they were during the testing of the FX board. The pot can now be installed onto the inverted scratchplate – with the loose signal wire from the tone circuit, finally connecting into the “C1” (signal in) control terminal.
And now – the final ground connections can be completed. The black, cloth-covered ground wire from the FX board is paired and spliced to the ground wire which leads to the jack socket. Attached together to a screw lug, and then screwed to the wall of the cavity with the other, lugged connections – this creates a central “star” ground point, where all of the ground wires converge. Now – the remaining loose ground wire from the previous lugged pair, is soldered directly to the back of the volume pot. The scratchplate, and it’s mounted components, are now physically tethered to the body – and the scratchplate needs to be carefully manipulated and inverted on the body of the guitar. Although it’s a “beaten-up relic” – it’s still a good idea to protect the body work with a cloth, or something similar. (There’s another running ground wire – connecting the volume and tone pots of the main tone circuit – shown in the image above. However – this wire was eventually removed during the final checks. It was essentially redundant, since the pots are all connected and grounded via the shielding plate, under the scratchplate).
The electronics can now be tested. With no battery in the clip – the tone circuit should still function normally, with the FX control set to off, or “bypass”. I’ve found that it’s often wise to test a guitar’s circuit, (at least initially), with the scratchplate off, and with all of the wiring exposed. If the circuit sounds “dead” at first – (which is exactly what happened here) – it’s a pretty sure fire indicator that there’s something wrong with the grounding somewhere… and with Stratocasters – I think I know exactly where the problem lies here…
Whenever I’m shielding a guitar body with copper foil – I have a habit of shielding all of the cavities – including, on Stratocasters – the jack socket cavity. What I’ve noticed – is that the way the cover plate is mounted over the top, can sometimes result in space at the back of the cavity, becoming a “little tight”. The insertion of the jack plug can then, occasionally, short either the tip of the jack plug to ground against the copper shielding, or it can push the retaining spring clip into the wall, with a similar effect. Either way – the signal is shorted, and there’s absoutely no response from the completed circuit. Looking at the jack cavity again – I don’t know if the shielding actually does anything, (the metal cover plate should be grounded via the jack socket itself) – so rather than cover any potential problem areas with insulating tape, (which works – but it’s layer on layer of redundant material) – I decide to simply rip out all of the shielding from the jack cavity.
The effect is immediate. Now – checking the pickup and tone circuit control functionality, with a Fender Mustang Micro amp, a pair of headphones, and a simple tap to each pickup with a screwdriver blade – I can confirm that it’s all working as it should. If a circuit is ever completely dead, (with absolutely no buzzing, or hum, or scratching when you touch the wires) – you can bet it’s a short to ground somewhere. (Trace the signal path, and rely on the knowledge of those insulated solder joints and conductivity checks you did earlier…)
I install a battery in the clip at the back, and power up the Micro amp again. With the second tone knob in the “down” position, (push) – the tone circuit continues to demonstrate functionality, as before, and there’s absolutely no background noise at all. Clearly – the shielding and the “true bypass” switch at the DPDT, push/pull control, are doing their jobs correctly. When I pull the second tone control out – the Fuzz circuit should engage. I’m not quite sure how I’ll be able to demonstrate functionality without strings on the guitar, but…
…Well. There’s clearly no doubt that something is happening. In fact – there’s a lot of noise…
At first – there’s so much noise – that I suspect there’s a reversed, or loose connection somewhere. I close the scratchplate down – in case it’s the overhead LED lighting which is exploiting the incomplete shielding – but that seems to make little difference. So – I open the whole thing up again, and double check all of the FX circuit wiring – checking point to point, and inspecting all of the solder joints carefully. A couple of loose-looking, suspect joints at the circuit board, are re-flowed and secured. Test again… still the same. I’m pretty sure it’s got something to do with the grounding – since the wires look to be in the right place, and whenever I touch the scratchplate, or it’s shielding – there’s an audible effect to the output. However – check as I may… I just can’t see a problem anywhere.
Then – I realise I have the Mustang Micro Amp set to the loudest of the various, possible, “high gain” modelling profiles. (The “Armageddon in a box” madness, of the “Bogner Uberschall” inspired setting – instead of the clean, “Studio Preamp” signal I thought I’d set it to). Change the amp… and… that’s so much quieter. There’s still a little bit of a hum with the effect engaged – but I’m pretty sure that these simple silicon fuzz units can’t be relied on for a clean output, anyway. If I spent another few hours fiddling about – perhaps re-routing the odd wire, or maybe shielding the thin, plastic covered, in/out wires from the FX board, which wind past all of the other controls and signal wires – I may be able to improve on things. But with the FX control dialled below about 5 – it’s about as quiet as I’d hope for and, importantly, it’s useable. I’m reminded that this is all an experiment anyway – and that I’m bound to want to change things about, in the future. Time to screw all of the cover plates down, and see how the guitar sounds with strings…
One last detail before stringing for the first time… three reliced knobs are pushed into place over the splined shaft ends of the control pots. With each control fully open – I first line up the “10” on the volume knob to face the adjacent pickup height adjustment screw, and then set the other two knobs to match that orientation. It’s a real shame Fender don’t make a control knob labelled “Fuzz”. A matching switch tip pushes down over the switch blade…
Finally – after a long, long build… I fit the guitar with a set of D’Addario EXL110 strings, stretch them out, and roughly tune the guitar. Now – with the guitar strung, (although not yet fully set up) – I can finally hear the Fuzz as it should be, for the first time…
…IT’S LOUD!!… …I SAID IT’S LOUD!!!…
In fact – it’s very loud indeed – displaying a “useable” range between only, roughly, 2 and 4 on the control dial. (That’s where “unity” appears to be with a fresh battery. Perhaps that might change as the battery runs out of charge???). Something about the circuit is apparently adding a certain amount of gain somewhere. Practically – as long as the control is kept turned down to unity with the guitar circuit – then the switch over is silent enough, and there’s plenty of Fuzz added to the Stratocaster sound. However – accidentally knock that control knob round a bit, and there’s plenty of potential to upset anyone unfortunate enough to be within earshot…
I’m no expert – but I’m pretty sure I could attenuate that output signal from the FX board, with an in-line resistor, (or something)… A linear taper pot might also stretch the useable range out a bit too(?). I’ll have to check up on things, and try and do a little more reading, and a little bit more experimentation, down the line. Ultimately – it could be that the simple circuit is just that little bit too simple – and perhaps a different board might give better results for this particular “built-in” application. Little detail changes to the circuit might make a practical difference… Germainium transistors always have the reputation of being more musical… there are a lot of possibilities to play with…
Meanwhile – with a suitable “reliced” finish, three quality pickups, and a working FX circuit providing more than enough Fuzz for a full-on psychedelic freak out – it’s about time this particular project moved towards some sort of conclusion, (for now, at least). Next – I’ll move on to the setup, and I’ll see what I can make of this “Road Worn” Fender neck…
Garageland 