The Absolute Basics
Never think you don't know enough to start fixing - the bar is probably lower than you imagine!
Résumé
Même si vous êtes doué en bricolage, vous hésitez peut-être à vous lancer dans la réparation d'appareils électriques parce que vous pensez ne pas en savoir assez. En fait, de nombreux défauts peuvent être vus de vos propres yeux, et des connaissances très basiques vous mèneront loin. Même si vous ne vous considérez pas bricoleur, une approche logique et un peu de curiosité peuvent vous mener plus loin que vous ne le pensez possible, et nous apprenons tous en faisant.
Safety
- Vous êtes probablement ici parce que vous savez que l'électricité du secteur peut être mortelle - félicitations ! Mais l'électricité joue un rôle équitable : si vous apprenez à la traiter avec respect (ce qui n'est pas difficile), elle ne vous mordra pas. Ne poussez pas votre chance !
- Les tournevis et certains autres outils ont des extrémités pointues et peuvent causer des blessures s'ils glissent.
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 simply need to think a bit about what you're doing. Here are a few tips:
First of all
- 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 and what might that tell you? What, if anything, has the owner already tried? Answers to these questions may help you narrow down the fault.
- Are there any signs of physical damage, or of overheating or burning?
- Follow a methodical plan. If the device is completely dead, first check the battery and battery connections, or for a mains device, the fuse in the plug and any fuses in the device. Then if possible, check for good connections from the battery or plug as far as you can trace them into the device.
Digging deeper
- If the device isn't completely dead, consider the various parts that make it up, for instance, a music centre might consist of a tuner fed from an aerial and a CD player, both feeding an amplifier connected to the speakers. A power supply powers all these. What functions (if any) still work should immediately enable you to narrow down your search.
- 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, try to work out if you can how it might do it. Close examination might be needed for mechanical parts. You will then be in a stronger position to discover why it isn't doing its stuff.
Mechanical Skills
To start with
You will need a few screwdrivers. The one from your grandmother's kitchen drawer might do, but a set of flat and cross-head screwdrivers in 2 or 3 sizes would be so much better.
You know which way to turn a screw? "Righty tighty, lefty loosey" is the easy way to remember.
Gaining your screw-driving licence
Using a screwdriver is easy, but a few simple tips are well worth bearing in mind:
- Before starting to take the device apart, take a good look at it. See where the screws are. If some have arrows against them, these are the ones to undo.
- Choose a screwdriver that's a good fit in the screw head, especially if the screw 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.
... and you still can't get the thing apart?
So, you've undone all the screws and you still can't get inside. 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 released with a thin blade such as a thin spatula inserted into the crack between the halves.
If it doesn't come apart easily, search online for the device make and model, appending the keyword "disassembly".
Electrical Skills - Battery Items
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.
Safety
Just two things to be aware of (take advice if you're not sure what to do):
- Take care with those cameras and flashguns in which the flash consists of a glass tube. These contain a capacitor which may retain sufficient 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.
Otherwise, you can safely work on virtually all items powered by a battery or small solar cell.
Rock-bottom theory
Water flows in pipes. Electricity flows in wires. Both can sometimes escape, and the result isn't good. You hardly need know more than that:
- 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. Think of Niagara Falls compared to a dripping tap.
Rock-bottom practical
- 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 circuit (a connection where there shouldn't 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.
Electrical Skills - 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.
The list of things you need to know is necessarily a little longer than previous sections, but if you know all this you should be able to tackle mains devices safely.
Electrical Practice
- 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.
In the real world
- A flow of electricity always 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 principal means of insulating an exposed wire or connection.
- A PAT test is strongly recommended after any repair and will be a requirement in community fixing groups. Most repair groups possess 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, which in practice, reveals the majority of faults.