Any comments welcome.

There is nothing more frustrating than a fault which comes and goes. Your guitar works perfectly all through every practice and then cuts out just as you do your big solo. How do the gremlins know when to get you?

I can’t anticipate every fault but some things go wrong more than others and I’ve fixed most things over the years (I am very old) so here’s a guide to finding and fixing the most common faults. This guide is aimed at someone who isn’t scared to use a soldering iron or who has a mate who can help but it could help you to save some money in the repair shop if you know a little about what is going on inside your gear

Any intermittent fault will be a so-and–so to find. Just as it will go wrong at all the most embarrassing moments it will work perfectly when you want to cure it. You need patience and to work methodically eliminating one thing at a time. Don’t make any assumptions, and always consider the possibility that you have more than one fault.

You have three things to consider: a guitar (mic, keyboard, whatever) an amp and the lead that connects them. Eight times out of ten it is the lead that fails, 99 times out of a hundred it is an electrical connection which causes an intermittent fault. Modern components don’t fail very often and when they do it usually leads to complete failure of the system and not something that comes and goes. Even when components fail it is usually because a connection fails where the wire joins them. The exception to this is in valve (tube) amps. Valves have a relatively short lifespan but when they fail they do not usually come back to life again. There are strands in the forums and columns on valves so I will leave valve failure out of this.

I am assuming that you are not using any pedals or effects and that if you have active electronics in your guitar that you have checked the battery.

Finding the Fault.

Always suspect the lead first. Every time you move the lead is wiggled and pulls a little on the connection inside the plug; eventually all leads break. If you cut out at a gig change your lead straight away (you do always carry a spare, don’t you?) at the end of the gig mark the lead you were using with some tape or by tying a knot in it. If you don’t you will get it muddled with your good leads. If using another lead fixes the fault permanently then the lead is at fault. I’ll tell you how to fix it later.
The next stage is to try another amp if the fault goes away permanently it’s the amp, if not it’s the guitar. If you don’t have a spare amp then try a different guitar. If it is the amp or guitar suspect the jack sockets first. Every time you push the plug in you are pushing dirt in and every time you wiggle the lead you wiggle the plug inside the socket and eventually the sockets fail. If the socket is failing then wiggling the lead near the socket usually makes the fault appear or makes the amp crackle. Remember at this stage you have eliminated the lead from your enquiries, it is easy to muddle these two faults.
The other symptom to look for is crackling. This is usually caused by a failing pot. (potentiometer) which is what we call the twisty things on the other end of the volume and tone controls. If you get crackling when you turn the controls then it is the pot. Inside the pot you have a long track with a wiper that slides along as you twist the control, varying the resistance as you go. Constant turning of the controls will eventually wear the track and often dirt will get in and break the contact. Another common problem with pots is that the nut which holds it in place comes undone and the whole thing twists inside your guitar or amp damaging the connections.
The last things which you can test from outside are the switches. Wiggle them and see if there is any crackling or cutting out when there shouldn’t be. Again the fault will be dirt, wear or a broken connection.

“I’m going in Captain”

If you’ve eliminated all the possibilities so far then it may be time for the repair shop. If you want to go on then a word of caution: amplifiers can have very high voltages inside them and can kill you. Not all of these voltages go away when you turn the amplifier off. Transistor amps in particular store electricity in huge capacitors that can stay charged for hours. Valve (tube) amps have extremely high voltages, much higher than the mains and the DC voltages in transistor amps give worse shocks than the mains. Never work on an amp that is plugged in to the mains. I’m going to assume that you won’t try poking around inside the amp unless you are used to working with electrical equipment.
Take the inspection plate off the back of the guitar. Put the screws somewhere safe (sticking them to an old magnet is good). You should see a little flat metal cylinder under each knob with three connectors sticking out of each, these are the pots. There are also little cylinders with coloured rings on them (resistors) and other electric components which can be a number of shapes and sizes (capacitors). There will be lots of wires connecting these all up. If your quitar is active there will be a neat little printed circuit board covered with mysterious things.
The first thing you are going to do is look very carefully at each component one at a time. Do they look damaged, have they come loose are they touching something they shouldn’t.
Now plug the guitar into an amp which is turned down low. Gently wiggle each component and wire one at a time to see if you can make the fault happen. If it does then you’ve found your fault. If the fault becomes permanent at this stage then don’t panic because you know exactly where the problem is.
Still not found the fault? The next trick to try is freezing spray which many repair shops use to find faulty components. Spray it onto one component at a time making it shrink suddenly showing up any dry joints or broken components. Listen while you do this to see if the fault occurs. You can buy a spray for about £5 or less in the UK.
By now you should have located the fault, if not go back and start again. If you still haven’t found it then I’m sorry but you have a problem which is beyond this guide.

You should have found one of the following problems:
• A broken or dry joint
• A noisy or broken pot, plug or switch
• A failed component
You should by now know exactly where it is but don’t forget there may be other faults to look for later.

Dry Joints and How To Fix Them

This is the name for a joint which has not been soldered properly. It may look good but inside there is something stopping the joint from making a connection. I’ve written the guide for someone who knows how to solder but here’s a reminder of how to do it just in case:
• Separate the joint by melting the solder
• Remove any excess solder with a solder sucker or de-soldering braid
• Clean the separated halves by scraping or with emery paper if you can see any dirt on them
• Now ‘tin’ the two halves of the joint with fresh solder.
• Hold the two halves together and join them with a little extra solder making sure that the solder on both halves has melted. Make sure the joint doesn’t move until it has set.
The fresh solder contains flux which will etch away a lot of the impurities and chemically clean the joint. Just applying the soldering iron to a dry joint may seal in the muck which caused the original problem and means your repair may only be temporary.

Cleaning Switches, sockets and Pots.

Amps and gear generally often work in difficult environments, cigarette smoke used to be a killer and I’ve spilled more than one drink on an amp (it was dark, what can I say) stuff gets inside switches and controls and pots get dirty and noisy. Fortunately you can buy spray cans of cleaning fluid specially made for switches based on petroleum or iso-propyl alcohol.

Try spraying switch cleaner in the jack socket or inside the pots or switches then plug /unplug the jack a few times or give each of your controls a wiggle. See if this has cleared the fault after the cleaner has evaporated away. If not then try a couple more times. I’ve found that this has about a 70% success rate but that components don’t always last very long once you start having to do this. Think of it as an early warning.
The other reason that pots switches and sockets fail is that the contacts inside them are usually made of nickel plated steel and overtime they corrode and or the spring weakens and they lose contact. Replace them, I have tried cleaning them and bending the springs but it is never very successful. It may get you through a gig but that’s all you should expect.

Replacing Components

Electronic components like resistors and capacitors are really cheap, usually only a few pence (cents) and rarely cost more than a set of strings, so replace them. If you need special manufacturer’s parts then look in the stickies in the forums for suppliers. UG is a great resource so learn your way around it. When replacing parts I suggest very strongly that you make a sketch of how it all looks before you pull anything apart. I always think I will remember and then find that I can’t get back to the job for a week giving me plenty of time to forget what I’d planned. Replace like for like, google resistor codes or capacitor identification to help you identify what you are looking at and make sure electrolytic capacitors are the right way round. UG gear building will help with most problems, look in the stickies.

I hope this guide will get you over the hump of knowing where to start. You have nothing to lose by just looking. The worst that can happen if you keep out of the amp is that you have to pay a repair bill you would have paid anyway. Oh. and expect a little teasing from the repair shop. Most of the gear I repair can be sorted with a spray cleaner or a soldering iron plus a little intelligence.
Good Luck
Have you considered an overall title for your series as of yet? You could edit the first one to fit if you do think of one.

I'm still concerned about the layout, but I know you let PiCSeL edit that and, having seen your article, it came out pretty good.

This is worthwhile and necessary in the archives. Keep going with it
Thanks Tom.

I know I need to improve the look of these but I tend to spend what time I have researching content rather than mastering the computer. I suppose that sounds a bit pathetic and I'll have to do it soon. Oh well.

Thanks for the encouragement.