Wiki

Never think you don't know enough to start fixing - the bar is probably lower than you think!

Summary

Even though you might be handy at DIY, perhaps you're hesitant to get into fixing electrical items because you think you don't know enough. In fact, many faults can be seen with your own eyes, and very basic knowledge will take you a long way. Even if you don't consider yourself handy, a logical approach and a bit of curiosity might get you further than you'd think possible, and we all learn by doing.

Safety

You're probably here because you know that mains electricity can be lethal - congratulations! But electricity plays fair - if you learn to treat it with proper respect (which isn't hard), then it won't bite you. Just don't push your luck!

Screwdrivers and some other tools have pointy ends and can cause injury if they slip.

Minimum Skills and Knowledge

The best way to learn fixing is to get stuck in and start doing it, ideally with a Restart or other fixing group with whom you can share problems and solutions. Experience counts for at least as much as head-knowledge.

Here, we set out the minimum skills you need under the headings of Logical, Mechanical, and Electrical.

Logical Skills

Some faults are visually obvious, but when they're not you need a logical approach.

First, establish what you can about the fault. Did it appear suddenly, or gradually, or after a long period of disuse, or after an accident such as a drop? If the device isn't completely dead, what still works and what doesn't? What, if anything, has the owner already tried? Answers to these questions may help you narrow down the fault.
Before starting to take the device apart, take a good look at it. See where the screws are. If some have arrows againt them, these are the ones to undo.
If it doesn't come apart easily, search online for the device make and model, appending the keyword "disassembly".
The most powerful approaches if you get stuck are Internet searches, this Wiki, and discussing a problem with another fixer.
Harness your curiosity. Given what a device is meant to do and work out, if you can, how it might do it. Or from observation, work out how it works. You will then be in a stronger position to discover why it isn't doing its stuff.

Mechanical Skills

You will need a set of screwdrivers, including both flat and cross-head, in several sizes. You can never have too many screwdrivers!
Know which way to turn a screw to tighten or to loosen it. The simple rule is righty tighty, lefty loosey.
Choose a screwdriver that's a good fit in the screw head, especially if it might be tight.
If you feel the screwdriver starting to slip in the head of the screw, press harder. If the screwdriver repeatedly slips you are likely to damage the head of the screw and make it nearly impossible to undo.
You've undone all the screws and it still won't come apart. Often, there's one more screw you've missed. It may be hidden under a label or a rubber foot. Plastic cases are often in two (or more) parts held together with clips. These can usually be reeased with a thin blade such as a thin spatula inserted into the crack between the halves.

Electrical Skills

Battery powered items are generally safe to work on but you need a good understanding (nevertheless, quite easily acquired) in order to work safely on mains items.

Battery Items

Take care with those cameras and flashguns in which the flash consists of a glass tube. These contain a capacitor which may retain suficient electrical charge to give you a nasty shock, long after the item is switched off.
Treat lithium batteries with respect. Shorting the terminals together or physical abuse can create a serious fire hazard.

Apart from the above caveats, you can safely work on items powered by a battery or small solar cell.

It will greatly help to understand the most basic principles of electricity:

Electricity can only flow if it can flow all the way around a circuit, from one battery terminal, through the works where it does something useful, and back to the other battery terminal. A switch in the "off" position or any break in the circuit will prevent the flow. This is known as an "open circuit".
Electricity generally flows easily through metals and to some extent through water or anything damp. (These are called conductors.) Electricity cannot flow through most other materials (known as insulators) such as plastics, rubber, wood, glass, provided they're dry.
Voltage (measured in volts) is a measure of electrical pressure, a bit like water pressure or air pressure in a tyre. All common types of battery (and small solar cells) only produce a few volts. Above about 50 Volts, electricity is potentially dangerous.
Amps are a measure of the amount of current flowing through a circuit.

You also need to be aware of the following practical apects:

If two wires touch which shouldn't, or a wire touches part of a metal case, this creates a "short circuit", offering very little resistance to the current. In the worst case, this may create a fire hazard.
An item may stop working or work unreliably if there are loose connections, dirt or corrosion on the contacts in a plug or socket, or in a battery compartment.
A simple multimeter is quite cheap and it's not hard to learn how to use. You can use it to test for an open circuit (no connection where there should be one) or a short circtuit (a connection where there's not supposed to be one). It's also easy to use it to test a fuse and to check for a weak or dead battery.
Faults may be indicated by signs of overheating, such as discolouration or charring on components or a circuit board. Also, learn to recognise swollen electrolytic capacitors and how to test rectifier diodes.

Mains Items

As you know, mains electricity is potentially lethal, and faults in mains electrical equipment can cause fires. If you are going to work on such items you need a good understanding of electrical theory, or be supervised by a more experienced fixer.

Mains leads consist of 2 or 3 wires. The brown wire is the Live and is the most dangerous. The blue wire is Neutral and carries the current back to the mains plug. The green and yellow striped wire (if present) is the Earth. In the case of a serious fault, this drains the current away from any exposed metal parts.
The 2 or 3 wires are individually insulated, and are all enclosed in an outer insulated sheath. The inner insulated wires must never be exposed outside a plug or the equipment, whether through wear, aging or damage, or through the outer sheath having been cut back too far.
When making a connection such as wiring a plug, make sure you cut back the inner insulation from the wire sufficiently far, but no further.
Any wire that could possibly be pulled, the outer sheath must be clamped to prevent any strain being put on the electrical connections.
A flow of electricity aways meets some resistance, which absorbs energy. According to the device, this energy might be turned into physical motion, light, heat, or it might be used to process information in a computer. Some will always be turned into heat.
A loose connection may have significant resistance, and if the current flow is heavy, this may cause dangerous overheating. Screw terminals and all other connections must be tight. Simply twisting two wires together will never create a safe and satisfactory connection.
PVC insulating tape must never be used as the main means of insulating an exposed wire or connection.
A PAT test is recommended after any repair. Most repair groups posess a PAT testing machine which checks the insulation and the integrity of the earth connection (if any), but a PAT test is not complete without a visual inspection as well.
The power of a device is measured in Watts (W) or kiloWatts (KW). 1kW = 1,000W.
Power is equal to Volts multiplied by Amps. Alternatively, you can calculate the Amps by dividing the Watts by the Volts (normally 240V). A Fuse rating must equal or exceed the Amps drawn by a device.