12-page pull-out: all you need to know
Ever had a problem with your favourite six string? A strange hum, an unwanted rattle? Over these 12 pages Adrian Legg plays box doctor and supplies a guide to common guitar faults, and how to cure them. Keep this and keep your hardware healthy.
First check that exactly the same thing happens when you plug into another amp. If it doesn't the amp may need servicing, but wait till you've checked your leads.
Undo the jack plugs, and check that both signal and earth connections are firm. Some better quality jack plugs have a threaded central core running up from the tip. It has a nut on the end inside the jack which contacts the signal solder terminal and holds the barrel assembly together. Check this is tight. Snip off any frayed wire ends and check that nothing shorts under strain. Plug the lead into the amp and wiggle it to see if it makes a noise. Clean the jack plugs with 1-1-1 Trichloroethane (see page 55). This can be bought as PCB solvent cleaner from an electrical component shop, as Tippex thinners, and as stuff for cleaning leather shoes prior to re-dying. Use it sparingly: the fumes can give you a headache, and it can damage soft plastic.
Next check out the jack socket on your guitar. It may be cleaned quickly with an aerosol contact cleaner (see page 55), but it is best to remove the assembly and clean it with Trichloroethane. Check that the tip contact presses firmly against the jack plug tip, and that this action holds the plug barrel firmly against the earth contact ring.
Check the solder joints. If they are old, remove the solder with a solder-sucker or desoldering braid. An old bit of co-ax outer cable can be used as braid. Trim up wire ends and resolder.
Be careful not to overheat and melt the central core insulation.
...need more careful attention. On some models, as well as pressing against the tip contact, the jack plug tip also pushes against a nylon insulator attached to a leaf, pushing the leaf against a second leaf to make a contact. This usually switches battery negative to earth and allows current to flow in the circuit.
Clean these two leaves thoroughly, and ensure that their alignment is such that when the jack is in, they touch, but when it is withdrawn, they do not.
Sometimes a simple stereo jack socket is used for power switching, and here the centre contact would carry battery negative to be shorted to earth by the jack plug barrel. If these contacts have lost their ability to grip through fatigue, the unit must be replaced, as must any jack socket with fatigued contacts.
When refitting the jack socket and plate, check that the screws have a good bite. If the screw holes have worn, glue in a matchstick or wood splinters and allow to dry before trimming off excess with flush end cutters. Then make small pilot holes and refit the socket plate. This check should be carried out whenever a plate is removed from any part of the guitar.
If you still have problems there are three possibilities. Firstly, the amp input socket needs cleaning. Switch it off and give it a quick squirt with aerosol contact cleaner (see page 55). Allow the cleaner to evaporate before switching on. Secondly, the co-ax in your leads has had it — if you bought them all around the same time, don't be surprised if they all wear out together. Thirdly, the problem could be further into the guitar.
The apparent source of a noise on an acoustic can be very deceptive due to the way sound comes off the guitar.
First check the obvious things, that strap-buttons and machine heads are not loose. Inspect carefully round the bridge for signs of lifting — use a fine feeler gauge to probe gently into suspect areas.
If you find a deep gap, slack off the strings and consult a repairman.
Check the truss rod adjustment where fitted — perhaps the adjusting nut is loose. On a new-ish guitar, the neck may not have settled forward fully, so just tighten the adjustment nut enough to catch, and keep an eye on the way that the neck settles.
If the guitar has a truss rod cover plate, cut out a piece of felt or soft leather the same shape and remove and refit the cover plate with the felt under it. This will eliminate one possible source of high frequency rattles.
...is the most worrying. It might be a strut or brace coming loose, and this requires a professional hand.
To check for it, tune the guitar to normal pitch, and lay it flat on a table with a couple of bath towels underneath it. Fold another towel tightly to support the neck. Damp the strings with your left hand, and tap firmly over the guitar top with the inside of your thumb. You should hear a firm but hollow thump, deeper over the centre of the top, lightening towards the edges. If you hear a dry click in the sound, you are over a loose strut. If you believe you've found something, slacken off the strings, reach inside the guitar, and very gently see if you can feel a slight movement in the strut. Consult a repairman if you can.
The same approach can be used to check I out the back braces.
Where the guitar has a pre-amp and pickup fitted, it is much more likely that these and the attendant cable will be the source of odd noises.
...is usually a symptom of a pre-amp that is too close to a brace or other part of the body, and is intermittently touching it. Undo the mountings and reposition the pre-amp body. It may be necessary to stick foam on the casing where it may touch if space is confined.
...can usually be traced to cables and cable stays or plips. One day the cable will hang clear, one day it won't. Vibration can cause a cable stay to break free. You will be able to relocate it by either looking for the glue, or a discoloured area where the glue used to be. Reglue it using a small amount of quick-setting glue — it is unlikely that you will be able to clamp it, and you might have to hold it in place while the glue sets.
Where excess cable moves into contact with top or back, twist it gently into a loop, and fasten the loop with an elastic band.
...usually indicate something small is loose. Check the mounting washers and spacers are all held tight. Check that the casing screws are doing a proper job. Where a self-tapper will not go fully tight, stick a little cloth tape around the hole. If the hole is badly worn, move up to the next thickness self-tapper. If necessary, open the pre-amp and check that circuit board mountings are secure, and that a badly seated component does not come into contact with the casing.
There is one very specific high frequency rattle that has so far been peculiar to Ovations, though it may show up on guitars using a similar switching jack socket. At one time it was such a pig to trace — even Ovation hadn't found them.
It occurs intermittently when the guitar is played normally, but can be exposed by playing a variable selection of 12th fret harmonics. If you try this and hear it, insert a jack plug, and it will disappear. Reach inside the guitar, and gently stroke the power switch leaves on the jack socket, and you will hear it clearly when the jack plug is removed.
Remove the socket, and apply a tiny blob of cyanoacrilate to the point where the insulation is pushed through the leaf. As it dries, stick on a very small piece of Blu-tac. Check carefully that no glue has dribbled down the leaf to foul the switch contact. If it has, remove it with a small amount of acetone, or wait for it to harden and scrape it off. You will find it difficult to remount the socket without the inside sprung washer falling off and running round the guitar. Use a small amount of Blu-tac to retain it on the socket barrel.
Where a box-type stereo power switching socket is used in a guitar, the solder terminals may rattle. They may be restrained with Blu-tac. Likewise battery clips, cables loose in cable stays, and battery cables.
...that come through on the signal are traceable to dry joints in the pre-amp. Remove it, open it up, and carefully remelt all the solder points. Do not apply heat to all the terminals of the same component at once, and do not apply heat for any longer than necessary to melt the solder. Nine times out of ten this will solve the problem. The tenth time, consult a repairman.
Dirt accumulating on the carbon track inside a volume or tone control can prevent the wiper (the contact attached to the spindle which moves around the track to vary resistance) from making proper contact with the carbon. This causes crackling when the control is used, and in extreme cases, signal failure.
On most pots used in guitars, there is an aperture in the casing by the solder terminals. Poke the spout of an aerosol contact cleaner/lube (see page 55) in there, and give it a squirt. If this doesn't sort it out, then the track or wiper is worn, and the unit must be replaced. It is not possible to clean out and lubricate a sealed pot, and this must be replaced. Replacements should be of the same value and law, unless you are varying deliberately for customising reasons.
Often the value and law will be marked on the pot casing — letter A indicates a linear track, letter B indicates logarithmic — but it may be that the manufacturer has simply marked a part number. If a stock replacement looks like taking some time to arrive, the track value can be measured easily enough, and it is possible to distinguish between linear and log on a good quality analogue multimeter, with experience. Try the local electronics shop if you need help — your major difficulty is likely to be the availability of the correct value with either a solid shaft or the correct size split shaft. American pots usually have a thicker split shaft than Japanese, as well as different sized mounting barrels.
Where a tone control doesn't work at all, check that it is properly earthed before replacing the capacitor. Its function is to short the higher frequencies selected by the capacitor from signal to earth.
Where a tone control has started to behave like a volume control, then the capacitor has gone and must be replaced.
When soldering capacitors, be sure to heatsink them. That is, use either Spencer forceps (got a first aid kit?) or thin nose pliers to hold the terminal between the capacitor and the solder until the solder has cooled. If it is necessary to bend the terminals, do it at a point clear of the capacitor body to avoid damage.
Noisy five- and three-way Fender style switches need cleaning and lubricating in the same way as pots. The contacts are exposed to dust and grease, which can get in via the slot in the scratchplate where the toggle comes through. Usually, regular treatment with an aerosol cleaner/lube (see page 55) will do the trick, but where persistent trouble occurs with a Japanese switch, it may be time to replace it with a better quality American component.
If you have to replace, draw a little reference picture of wires and positions before disconnecting, but bear in mind that positions may be reversed on some switches. Because the contacts are all exposed, you will be able to see clearly which are made or open in which toggle positions.
The Switchcraft-type leaf toggle switches, like those fitted to Les Pauls, may also require periodic cleaning, though they are less exposed as a rule then Fender style units. Over time, the leaf contacts may fatigue and deform, in which case the unit must be replaced. Check first though that the nuts and bolts holding the block of leaves and insulators together have not worked loose to cause a misalignment.
Japanese box-type selector switches are not capable of cleaning, and should be replaced in the event of a defect, as must the sealed mini toggle S/DPDT switches used for coil switching. The latter are susceptible to heat damage, so do not apply heat for any longer than necessary to make a clean solder joint.
Hum comes in different varieties. The first we shall deal with is bad string earthing.
Plug the guitar into a properly earthed amplifier. If there is a loud hum which decreases when you touch the strings, the string earth is defective.
If you look in the control cavity you will see a wire which comes out of a hole in the cavity wall. Check that it is connected to either the jack socket earth or to an earth point in the guitar. If so, give it a gentle pull — it should be firmly connected to the bridge at the other end of that hole.
On Strat type tremolo bridges, the string earth is usually soldered to the plate from which extend the tremolo springs. If it needs resoldering here, it is best to remove the tremolo springs to reduce the heatsink effect. You will need a pretty hot iron anyway — a tip temperature of over 400 degrees C should do it, but on thicker plates I have had to use a heavy duty iron.
On guitars with a screw down plate type bridge, the string earth usually emerges from the body under the bridge, and contact is made by the body pressing the wire against the underneath of the bridge.
Where there is a pillar mounted bridge and tailpiece, things are more difficult. The end of the earth wire usually emerges in one of the holes drilled to accept the metal sleeve which is internally threaded to take the adjustable pillar. Removing one of these sleeves really needs a professional repairman as the risk of finish damage is high. On a new guitar this would be claimable as a warranty matter — inserting the pillar sleeve into the hole probably sheared the wire.
...according to your position in relation to your amp, it can be reduced by improving the screening around pickups and controls in the guitar. All the internal cavities should be lined with a commercially available copper foil. This stuff has a peel-off backing and sticks easily, but be careful you don't pick up a cut from a sharp edge. Each piece should be soldered to the next for electrical continuity, and the whole connected to the earth at the jack socket. All pot and switch casing should have a proper earth contact, and this should be soldered rather than relying on purely physical contact with foil.
Single coil guitars are far more prone to this sort of hum than dual coil. The humbucking principle reverses phase in one of the coils of a dual coil pickup, so that as one coil "hears" electrical noise as peaks and troughs, the other "hears" it as exactly opposite troughs and peaks, so they cancel each other out altogether.
It is still likely, though, that humbucking fitted guitars will need further shielding.
Remember that operating a coil-tap knocks out the humbucker's ability to cancel hum, but parallel coil switching does not.
...check that all solder joins are properly made and that earth contacts are solid. Check for frayed and loose wire ends, and for shorted co-ax. Consult a repairman if nothing shows up.
So the meter says your open strings are in tune, but as soon as you get up the neck a bit it sounds terrible. You have three possible solutions, assuming you haven't refretted to a modal scale.
Old strings get corroded, stretched unevenly, and collect dirt in the windings. Any of these things can cause them to vibrate unevenly or at a different rate from normal in different areas. Nylon trebles particularly, can stretch into lumps and thin bits, but corroded steel strings can sound just as bad. If they are much more than a month old and you play a lot, or if there is any bad discolouration or rough feel, change them. Remember corroded strings will wear your frets much more quickly.
At the half-way point of the strings is a harmonic which is supposed to be the same pitch as a note played at the 12th fret. The 12th fret is halfway up the scale to the bridge. If you move one saddle (on an electric), 2mm towards the nut, then the harmonic halfway up the strings will move towards the nut 1mm. Exactly the same applies in the reverse direction — the harmonic will move half the distance the saddle moves, in the same direction. Add into this equation the necessity for compensation. If a string is 2mm above the 12th fret, then pushing it down to fret it bends it out of line by 2mm, increases tension, and thus raises pitch. Therefore the saddle must be set a little further away from the nut to allow for this. Also, a saddle must be set back further for a thick string than a thin one to allow for the fact that a thick string starts vibrating at point slightly | further forward of its take-off point than a thin one.
Simply, if the harmonic is sharp relative to the 12th fret note, move the saddle and harmonic towards the nut. If | the harmonic is flat relative to the 12th fret note, then it must be pulled up the fingerboard by moving the saddle away I from the nut.
...on the treble strings, the open tuning is fine, but no way can you get a sensible note out of the wound strings further up the neck. This is because magnetic pull from the pick-ups is interfering with the free vibration of the strings and causing a double note, or shadow note. Lower the pick-ups, the problem will go away, and you can set your intonation.
First check that the twisted back section around the ball end is not coming undone. Some coated steel trebles are | particularly prone to this under hard finger-picking.
Check your machine heads for wear in the worm and gear — on a sealed unit a lumpy feel on the turn is the clue. Replace the unit.
Check that the nut is tacked down properly with glue, and not slipping sideways, and where appropriate, check that neck bolts are tight.
Check that the small worms on individual saddles are not working loose through vibration. If they are, remove them, paint nail varnish onto the threads and replace them. It is not advisable to use a proprietary locking compound, even a temporary one may well prove stronger than the hex sockets or screw slots at this small scale.
If they go every time between nut and the machine head, check that the nut slots are wide enough for the string, and lubricate them. At the bridge, check for sharp edges, and reduce any with a small file, being careful to leave a clear takeoff point. Check for nicks in the fret surfaces which might cause a string to catch and kink — see a repairman if they are damaged.
Otherwise, don't hit it so hard.
If it's even all over the fingerboard, raise your action unless you like sitars. It takes a good set-up with fine fret levelling to get to 1mm first/1.5-1.7mm sixth string, and this will be too low for all but a light right hand, and won't bend well on a high camber fingerboard.
...fret buzz indicates incorrectly set neck relief. The relief must be increased by slacking off the truss rod so that the neck moves into a forward curve. Check it roughly by holding down a string at first fret and around the fourteenth. The tops of the frets should curve gently away from the string, with the maximum distance around frets five to seven. If all the frets touch, then the neck is straight or curving back, and the truss rod must be slacked off.
Use the correct size wrench — if one has not been supplied with the guitar, check with dealers/distributor.
Most truss rods will only force a neck back or relax it forward — very few actually push it forward — so an overtightened neck may take a while to settle forward where light strings are used. It is better, therefore, to let a neck come well forward , and then reduce relief gradually to the correct level. A neck tl will not relax forward needs professional help. You may measure relief with a straight-edge and feeler gauges. The usual minimum for a light player would be 5 thou in, and maximum, for a harder player, 15-20 thou in. Remember that the neck may keep moving for a while after the actual adjustment, so spread the operation over a few weeks, adjusting a quarter turn at a time. If a tight neck will not move initially, leave the rod > slack for a while and keep an eye on it.
A groove worn in a fret is obvious, and if that note buzzes, then it is time for fret dressing or a refret. Both require experience for good results.
Where the fret is not badly worn, check that the next fret up it is not springing out of its slot. If it is, it must be pulled and reset — simply tapping it down is likely to make matters worse. Again, really a pro job if you want good results.
First check for wear and springing. Then check that the relief has not increased unnoticed and the action been lowered without relief adjustment. If this is so, then raise the action and reduce the relief.
If this relationship is ok, then look for signs of the fingerboard end humping up. This can be caused by the wedging action of the fret tangs against a less firm base than down the neck on an acoustic. If the fingerboard top end is secure, then the cure is a shoot and refret — a pro job — which involves fret removal and planing down the warped board. On some guitars, notably Ovations, necks were pitched back and the fingerboard end simply curved over the table and glued rather than left straight and supported with a wedge. Sometimes on a bolt-on neck, removal of some of the wood underneath the hump can be effective, but consult a pro, the possibilities for disaster are quite significant.
A hump in an electric fingerboard will require a shoot and refret, but free-floating fingerboard ends may be expected to vary with the weather — my Adamas predicts rain or sunshine.
If open strings buzz, check first that fret 1 is not springing, and check that relief is correctly set. Otherwise, the nut slots have worn too low. There are two temporary solutions.
The easiest works best on bone nuts. Fill the worn slot with epoxy, and leave it to harden fully. This may take 24 hours, but check on the glue packaging. Once it is hard, recut the slot to the correct depth, using a feather-edge file or razor saw for the trebles, and an appropriate needle file for the basses. Tape the headstock up to avoid digging into it with the file ends, and work from the fingerboard side so that the slot bottom slopes down towards the headstock. This will ensure that the string take-off point is at the fingerboard side of the nut.
Alternatively, the nut can be removed and shimmed. Put a file or straight edge end against the nut from the fingerboard side, and tap the end smartly with a light hammer. Nuts that fit into a slot, for example on a Strat, need care. If you cannot push it out sideways using a pin-punch and light hammer, consult a repairman or resort to filling the slots and recutting. Once the nut is out, cut a piece of thin plastic or brass shim to size and stick it to the bottom of the nut. Reposition the nut with a dab of glue. Cyanoacrilate works fine for this in small quantities, because it has a fairly low shear strength that will not impede a later replacement job.
If a stock replacement is available, then the job is simply a matter of removal of the old nut, and positioning and gluing of the new one. Once fixed, the slots may be cut to the correct depth.
Making a new one from a brass or bone blank is a more skilled business.
You may like to have a shot at it using the old nut as a reference for shape and size, but an expensive guitar will benefit from a pro job.
Check that there is a good break angle over the saddle, particularly on an acoustic where the whole bridge may have been cut down to lower action. If there is no further room for manoeuvre, it may be necessary to have the neck removed and repitched, needless to say, a skilled professional job on a fixed neck guitar, but simple on a bolt on neck.
...on a three point mounting Strat is simple, the bolts must be slackened off, and the worm tightened or loosened. On a simple four point mounting, remove the strings, undo the neck bolts and remove the neck. Cut a piece of shim to fit into the neck slot in the body just up nearest the bridge. Tack it down with glue so it doesn't slop around while you're putting the neck back in. Once the bolts are tight, raise the bridge to meet the new neck pitch, increasing the break angle and downwards string pressure.
Check that the bridge take-off point is clear, and that vibrating string does not foul a rounded or scarred saddle top. Check that any springs in the adjustment have not fatigued and still fit tight — remove and stretch any sloppy ones, or replace. Check that the adjustment screws are not working loose under vibration (see Slipping Tuning for cure).
As always with buzzes, bear in mind that you may not hear clearly where it is coming from, and check all screw-on body parts for firmness.
There is manufacturers' advice and painful experience. What follows draws on the latter.
Firstly, everyone in the world wants to nick your guitar, except your immediate family. They want to destroy it. A family home is a dangerous place to keep it — vacuum cleaners are notoriously insensitive, and crawling babies love the sound a Martin makes when struck firmly with a teething ring. Cats rub their backs against unstable guitar stands, and leave fleas in case linings. Central heating dries guitars out, and visitors sit/stand/trip/ spill-coffee on them.
Don't leave your guitar in the car at any time. Diz Disley may have left his safely in the hedge overnight — take yours indoors. The one night you leave it in a residency will be the night they forget to lock the fire escape/the sprinklers malfunction/the chef smashes everything in sight with a meat cleaver.
Do not leave it at a gig while you nip out for a quick local radio interview/MacDonalds unless someone has locked it in the office, or you have a lockable dressing room.
Do not accept offers of help loading-up, unless you are dead certain you know who is offering. A band can keep the stage and the van both covered. Working solo or duo, keep your eyes skinned and lock the car every time.
A padded gig bag or light case is all right for a solid for the odd local gig if the guitar is not going in a bandwagon.
Check out your car and boot floor for hot spots from the exhaust, or a traffic jam might split something.
If you are going to travel or gig steadily, you must have a good hard case. Casemaker Keith Calton can make one to fit for less than the cost of some production cases, and some guitarists fly his cases regularly. He is at 0252 314300, 6 Grove Road, Ash, Hants. GU12 5BD. Care 4 Cases are fair value, but check for top flex. Also check that when any case studs come off, the metal rivet is removed — it can be pushed into the case and damage the guitar.
Where you have a colour option (as with Calton), choose white. It reflects radiant heat best, and shows up in a darkened backstage area.
A heavy duty flight case may be tempting, but remember that its weight and bulk may be very inconvenient. It can be like carrying a battering ram around with you, and may not fit in a car or taxi. Flight cases are really for large scale shipping. Their pose value is doubtful — the guitar may be mistaken for a disco deck.
Travelling by train, admit defeat gracefully and put the guitar in the guard's van before the ticket collector falls over it. Label it with your destination station, and be sure the guard knows about it. Check out the stop times before yours in advance; hover discreetly when it stops.
Make a fuss at airports. Do not let them shove your guitar on an automatic baggage destruction belt — insist on hand-loading, and airline muscle will dutifully turn up and collect it. Disembarking at tubular hell-holes like Heathrow is more difficult, but a word with cabin staff during the flight may persuade them to check that the guitar is taken to baggage reclaim by hand. Generally, take the absolute minimum and insure it — airline baggage damage maximums will probably not cover you.
Cleanliness is next to less fret wear. Wipe your strings after playing because it slows down corrosion. Bin corroded strings immediately you discover them — the harsh wire will cut into your frets and wear them prematurely. Clean a gungy fingerboard with meths, and polish discoloured or corroded frets with Duraglit.
Restring a whole set one at a time, it makes it easier to settle the new strings in and tune up. On a light, whippy neck, it also retains a more constant string versus truss rod tension, but removing all the strings occasionally to clean the fingerboard does no harm. Changing overall gauge of strings may affect the neck relief — see Fret-buzz section p49 — by exerting a greater or lesser pull on the neck.
Don't use polishes with silicone in them, or you will make life very difficult for anyone doing a future finish touch-up. Finishes will not stick on silicone, and getting rid of it can be difficult.
Finally, where fix-it-yourself is concerned, take your time. Don't do something until you have figured out how to undo it if it goes wrong. If you need advice, contact a reputable repairman. Check round fellow guitarists to find one, ask local pros, or your local MU branch secretary. People who work in shops are there to sell things. They don't have to understand them, and many don't.
Feature by Adrian Legg
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