Guitar building question- electronics

[caden_vekk]

yeah its the Senior Project, basically if i fail it, there is no possible way (even if i have a 100% in all my classes) that I can graduate

[dfung60]

Hey guys...  Been swamped with a project and haven't visited in days.
 
terryc already responded on the jack plate question.  The shield in the cable is connected to the sleeve connector of a phone plug (the big connector that comprises most of the plug length).  The center conductor is treated as the hot signal line and is connected to the tip portion of the phone plug.  The threaded barrel portion of your output jack (the part where the locknut holds it in place) is normally grounded, so the jack plate would be too.
 
However, I don't think it's good practice to use the jack plate as ground.  You wouldn't use one on a guitar, but there are plastic bodied output jacks (cheap ones) that may not even have a metal barrel and might not automatically ground the jack plate.  Even if the barrel is metal and grounded, if your output jack becomes loose (and who hasn't had this happen?) then you'll lose your grounding.
 
The right way to do this is to attach a wire to the ground lug of the output jack and run that to a central location in the control cavity that can provide a ground for everything in the instrument.  On most traditional guitars, there's a wire from the jack ground lug that's soldered to the back of one of the pots.  Wires from the other ground points on the guitar (which would include the bridge and internal shielding) also run to that point.  In theory you can chain grounds together and it should work, but it will be more reliable if they all come to one point.  If you want to have a fancy ground setup, you put a threaded insert into the wood in your control cavity, put ring lugs on the wires that run to ground and screw them all together using a machine screw into the insert.  
 
Using foil or conductive paint shielding in the pickup cavities blocks interference coming behind you, and will help keep your guitar quiet.  If you doing shielding anywhere in the body, you need to have a quality, low-resistance electrical connection between the shielding and the ground.  The way that this is typically done is that you cement a piece of copper foil into the cavity, then paint over it with the conductive paint or touch it with the copper foil.  You scrape the paint off of part of the foil, then solder a wire to the foil.  The other end goes to the normal ground point.
 
You want all parts of your grounding system to be well connected electrically.  Remember that your electrical ground is the same signal as your signal ground.  If there's a poor quality connection anywhere in the ground connections, that looks like a resistor was inserted inline in your signal.  That can reduce your output level and affect your tone.  Proper shielding should have no affect on your guitar tone, just on the noise.  But if you have a cold solder joint or other poor connection, you can easily end up losing treble.
 
When I was in junior high, I had a Fender Bassman tube amp and my guitarist had some similar setup.  We'd practice in a basement, so we had all the elements of doom - good ground on the basement floor, 2-prong plugs, two amps which had polarity death switches, and a little PA.  You'd kind of play a while until you got shocked, then you'd flip your polarity switch and play until you got shocked on something else.  I guess we were too dumb to use a continuity checker.  In Europe with 220v, I think this is a lot more serious than a tingle.
 
Good luck with your project.  Write again if this doesn't make sense.  I'm still in the thick of my project, but will find time to visit again.
 
David Fung

[terryc]

David..yes 240 in th UK so even more 'tingle' which I can vouch for!!!!
Over here all sensible people use RCB plugs to protect ourselves.
Caden vekk..The only advice I can give is that although the deadline is soon don't try and cram every hour of the day into it..take a break from the build and go back to it..it makes all the difference.

[cozmik_cowboy]

And, of course, post lots of pictures of the finished product (and the build, if you have them).
 
Peter

[terryc]

yes  let's look at all that hard work!!!

[caden_vekk]

I've got tons of pics of the build and progress as of yet, I'll post up some of the pics i have. Would this be the place to post them?

[caden_vekk]

I'm back again and ready to make my baby a cyborg so I need some help with the electronics. My setup is two humbuckers with a 3-way toggle switch and a master volume and master tone. I've got both 250 and 500 pots for those and I've forgotten which value goes better with which function.  Anyway, I'd like to have the toggle functions as: Top Position (switch head pointing towards sky): Neck Pickup Middle Position (switch head pointing straight out) Both pickups Bottom Position (switch head pointing toward floor) Bridge pickup. With the given photo's, do you think this setup will be possible and if so how would I connect all the wires and such?  The Setup, basic i know

  Setup in the back

  Position "Top" as seen from playing position, I would like this to select the neck pickup.

  Position "Middle" as seen from playing position I would like this to select both.

  Position "Bottom" as seen from playing position, I would like this to select the Bridge pickup

  Wires. White is neck, Yellow is bridge

[dfung60]

A fairly easy setup.  This diagram shows you how:
 
http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=2h_1v_1t_3w
 
You normally use 500K pots for humbuckers, 250K for single coil pickups (the 500K pots will have less treble roll off which generally mates better with humbuckers that have less treble to start with).  
 
I'm not quite sure exactly what I'm seeing with the the wiring.  If these are normal passive humbuckers without coil taps, then the pickup hot wire will normally be the center conductor inside the fat yellow or white coaxial cables.  The signal ground is the foil shield around the center connector.  I'm not sure what the red and white wires are and your fingers are covering up where they're emerging from in both cases.  Looks like they're emerging from the heat shrink cover that's been applied on both pickups and I don't know what they're there for.
 
In the Duncan diagram, they have the red & white wires from the pickups tied together.  These are outputs from the individual coils which would be used if you had a single-coil or series/parallel switch.  You can just ignore those.
 
The best way to get your 3-positions switch set up properly the first time is to test for continuity with an ohmmeter or continuity light so you can see which position of the toggle turns on which terminal.  Write back if you need more info.
 
David Fung

[caden_vekk]

Mucho Graciasness, Dfung. Yeah that helps a good bit. All i have to do is figure out which wire color i have matches which color of the black, green, and bare of thiers'.  
 
It looks as though the black(mine) is black(SD), that's good. That only gives a few possiblilities on the other two. Looking at this, though, it seems as though, it doesn't really matter as long as the black wire of the neck pickup goes to the 1st position tag of the 3way. I'll give you a mock up with mechanical connections later on today or tomorrow. Thanks D

[dfung60]

Having 3 wires on the pickups is pretty odd.  Where did you get these pickups?  
 
EMG actives (e.g. not HZ or Select pickups) have three wires - a hot and ground for signal which is a coax cable (the ground is a shield around the hot signal conductor).  The third wire is the DC power (9-27 volts) to power the pickup's internal preamp.  The power ground and signal ground are the same on EMGs.  These pickups aren't EMGs, but if they are active with that sort of setup, then you won't get any output unless power is applied to the proper wire.  Also, all the lines will look like open connections to your ohmmeter.
 
Humbucking pickups (like your picture) have two coils, each of which has two end wires, which are the normal 4 wires you see on many humbuckers.  If you connect up pairs of wires to an ohmmeter, you can see which wires are on the ends of each coil - you'll read a resistance when you have a pair that are on the same coil, open circuit otherwise.  If you switch one of those pairs to the output, then you'll get a single coil sound (wimpier than a Strat or Tele pickup, but brigher than the humbucker).  Wire both coils, either in parallel (normal) or series and you'll get a humbucking sound.  To get the humbucking right, you have to pair the right ends of the coils together, otherwise the result will be a thin, out of phase tone.
 
Three wires is weird as it's not any of the obvious possibilities.  I'd be interested in getting a close-up picture of where the white and red wires emerge from the bundle.  The black wire (actually not black, but that's the color of the shrink wrap insulation tubing that was applied over it) is probably a coax cable - if you strip the outer insulation, you should see a braided metal shield which is one of the conductors.  If you push that braid back, there should be an insulated wire inside of it which is the signal hot conductor.  That center wire is the one that goes to the switch; the braid would connect to the ground, usually on the back of one of the pots.  If the black wire is coax, then you do have 4 wires total and the pickup is slightly less weird, even though it's odd that all four of the wires weren't in the shield.  
 
David Fung

[u14steelgtr]

Will; David Fung did a superb job of covering a lot of important points; so kudos to David! But I thought I would take a stab at re-stating what he wrote in my own words and adding a bit more information and explanation.  
 
First a couple of terminology points which may prove helpful to you and others now and in the future.  The terms ring and sleeve tend to be used interchangeably by guitar players and builders but they are not exactly the same (this is pretty banal stuff but it matters when one is discussing the nuances of electrical shielding). A sleeve is the portion of a connector which provided shielding. The ring is the outside contact on a coaxial connector; however not all coaxial connectors are shielded. For example the basic no-frills 1/4 jack which is mounted on the front of a pre-amp or an instrument amp has a ring and a tip but is not shielded connector by design; when these connectors are installed the shielding is usually provided by the conductive chassis.  
 
It is conventional to ground to the ring of the output jack as this continues the cable shield circuit in to the guitars shielding system. If you have a conductive jack plate connecting the ring of the connector to the jack-plate can enhance the shielding of the instrument.  Some output jacks insulate the ring on the connector from the mounting nut and some do not; when the ring is insulated from the mounting nut it is normal to add a jumper from the ring to the jack plate (if the jack plate is conductive) to further enhance the shielding system.  
 
The guitars shielding system is typically comprised of copper foil inside the pickup cavities, the control cavities/cavity, and in some cases (like stratocaster instruments) between the pick guard and the various cavities. All of this foil is all connected (or literally wired) to the ring on the jack ultimately.  Some companies including Alembic use conductive-paint instead of foil as a shielding material. Also one usually also runs a ground wire from the shield/ground/earth to the bridge so that the bridge, and often the strings will further shield the electrical components of the instrument. The grounded bridge is why touching the bridge and/or strings will reduce the hum on many older and more primitive instruments.  
 
On instruments which have a non-conductive or poor-conducting bridge saddle or saddles (usually this only occurs on instruments with synthetic saddles) it is sometimes a good idea to ground to the metallic tail-piece or the retainer on the ball-end of the strings. But this is the exception and to the rule The objective in this case is to electrically connect the strings to the instruments shielding system.  
 
All of this brings me to pointing out that the pictures of your control cavity which were posted last weekend did not show any shielding at all.  
 
Regards
-- Eugene

[dfung60]

Eugene -  
 
Actually, I think you may have the conductor terminology mixed up a bit.  The names tip, ring, and sleeve date back to phone company days and refer to the conductors of a 1/4 phone plug and jack.  If you look at a regular 2-conductor 1/4 jack (like a standard guitar plug), the tip, not suprisingly is the pointed tip conductor.  It's the hot side of the signal pair and would normally be wired to the center conductor in a coax cable.  The long conductor that reaches from the tip to the handle is the sleeve and is normally connected to ground.
 
If you look at a 3-conductor phone plug, which used to be the common plug for headphones and is the stereo 1/4 out on older Series Alembics, you'll see that there's another conductor that sits between the tip and sleeve.  The conductor is actually shaped like a little ring, so this is, not surprisingly, the ring.  This conductor would normally be a second hot signal, for the other channel.  At these levels, the ground is usually common between all channels.  The 1/4 jack example you cite actually has a tip and sleeve connector, not tip and ring.  
 
On coax connectors like the F-connectors used on your analog TV antenna or BNC connectors used on electronic test equipment, the rotating part which screws or latches down is electrically connected to the shield in the cable to continue the shielding all the way between devices you're connecting.
 
David Fung

[caden_vekk]

I looked up the humbuckers Stewart MacDonald Vintage golden age overwound humbuckers. There are only the three wires. http://www.stewmac.com/freeinfo/I-GOLDEN-AGE.html
 
This is saying something about To wire the pickups as a standard humbucker, the red wire is hot and the bare wire is connected to ground. The white wire should be taped off so that it won't come into contact with other wires or components.

[dfung60]

Boy, that's a pretty weird way to wire a pickup.  The way that this works is that the coils are wired in series, so when you use the bare (shield) wire and red wire it works as a normal series humbucker.  In this mode, it's like you're using the the black and green wires from a Duncan and white and red are tied together (you can see the color code for Duncan at http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=color_codes).
 
When you switch to using the bare and white wires on your pickup, you just get one coil.  The white pickup wire is wired as if it were connected to both the white and red Duncan wires.  The pickup red wire is no longer connected to anything, current can't flow in that coil and you get the single coil effect.
 
I guess they did this to make the coil select switch less complicated (it only needs to be single pole instead of double pole, which means it's only switching one set of wires instead of two).  
 
Should work fine though!
 
David Fung

[caden_vekk]

Would i connect the black wire to the 3way and the red to the volume pot? Should i just tape off the white wire then or what?