Pot Replacement - "Pot" stands for potentiometer. Volume and Tone pots are the same component but a capacitor is soldered to the ground lug of the tone pot which prevents a certain amount of treble from grounding out. Scratchy pots can often be improved by using an electronics cleaner which is sprayed into the opening of the pot casing. Once sprayed you should rotate the pots knob from one extreme to the other several times to clean.
DeOxit Cleaner
Types of Pots: For DIY'ers who are trying to replace a volume or tone pot in their instrument you will need to know what you're looking for....
Linear or Audio pot? Audio is the most popular but check the manufacturers diagram for more info.
Value? Which is to say their resistance or OHM Rating. (250K, 500K, 1 meg etc)
Split or Solid Shaft? Split shafts use press fit knobs, like a Strat. Solid shafts require a knob that is fitted with a small screw to hold it to the shaft.
Long thread or Short? Longer threads are necessary for many carved top instruments whose pots do not mount on a thin pickguard (ex. Les Paul).
Regular or mini size. Mini pots are often necessary when mounting controls in cramped quarters such as those with active electronics.
Some pots will have the information stamped into the casing but if you are unsure you may wish to check the manufactures site for a wiring diagram or schematic for more info. You can experiment with different value pots but most commonly you will find 250K pots used with single coil pickups and 500k pots used with humbuckers.
Switch Replacement - Switches can wear out or break and on some instruments where cheap components were used they simply need to be upgraded. Again, if you are a DIY'er and the instrument needs a replacement you can refer to the manufacturers diagram for more info. You can also compare the number of soldering lugs, switch positions (3, 4, 5 etc.) and the spacing between the mounting screws (this is usually only an issue with some imports) to find the correct replacement.
Wiring Repair- Most often this is a problem on vintage instruments who have seen better days or those that have been improperly repaired. Loose wiring, cold solder joints, broken connections and burnt insulation can all cause problems.
It is quite common for solder joints to break if the input jack becomes loose enough to allow the input jack to turn freely in it's mount.
Shielding - Shielding can be done by lining the instruments cavity it with special adhesive backed copper foil (see picture below) or heavy duty aluminum foil which can be sprayed with adhesive. On the instrument below I have lined the control and pickup cavity with cooper foil (using solder to bridge the connection between each piece of foil used), as well as the back side of the pickguard. The "tab" of copper will act as a connection between the pickguard and cavity.
Rewiring / Repairing Broken Connections
Archtop Wiring
Above you can see what a time consuming pain electronics repair can be on some archtop/hollowbody electric guitars. Because of "chain gang" wiring, where each component is linked to the next, in some cases all parts must be removed to replace one. Prices to repair these are based on a flat, per hour fee as they can be most time consuming and aggravating.
In comparison, pickup, pot, switch and jack replacement is a piece of cake on most solid body guitars.
Tips
Removing Stubborn Knobs
Stubborn knobs can often be removed by wrapping a thin rag around the base of the knob and using it for leverage. I've also used guitar picks, one on either side) to lift the knob up...the point is to use something that can not damage the finish....screwdrivers are not a good choice here. :)
Also note that this is a split shaft pot...the knob is merely pressed on. Solid shaft pots require a different knob that has a small hex screw in the side which tightens against the shaft to hold in place.
Removing a tight knob from the pot
Repairing Loose Knobs
When press fit knobs like the one shown above are loose and come off too easily simply place a strong thin object (like a dime or a thick pick) between the two halves and gently spread them until enough pressure is created to hold the knob in place. Repeated spreading and squeezing can fatigue the shaft enough that the it breaks so be gentle.
Knobs for Split Shaft Pots
On solid shaft pots that use knobs which are held in place with a small hex screw years of use can also make these loose as the screw wears a channel in the shaft. More than likely if you remove the knob you will see where the screw has worn a groove around the diameter of the shaft. If you don't care to replace the pot you can raise the knob just enough so the screw will sit on an unworn part of the shaft.
Knobs For Solid Shaft Pots
Finding a wiring diagram
Some web surfers contact me looking for a wiring diagram for a odd or no name guitar as they have found no such info. and they are not sure what to do. First of all let me explain that if you have an electric guitar that is similar to lets say a Strat, in that it has 3 single coil pickups (and they are 2 wire pickups), one 5 way switch, 2 tone pots and 1 volume pot then you could use a Strat wiring diagram for your wiring plan. It's often easiest to think of the instrument in terms of equipment not brand. You can also visit a number of pickup manufacturers websites for a host of diagrams and wiring possibilities. For instance, Seymour Duncan's website has a host of wiring possibilities for several different pickup/control configurations.
Wiring an instrument or simply replacing a faulty component or pickup is usually a very simple repair if you know how to solder and follow a wiring diagram. The web is a great resource that can give you the basics on soldering but if you doubt your ability I would of course recommend letting a shop handle it for you.
