The Absolute Basics: Difference between revisions

(Key points highlighted.)
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=== First of all ===
=== 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.
*<span style="background-color:yellow">First, establish what you can about the fault</span>. 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?
*Are there any signs of <span style="background-color:yellow">physical damage</span>, or of <span style="background-color:yellow">overheating or burning</span>?
* 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.
* <span style="background-color:yellow">Follow a methodical plan</span>. 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 ===
=== 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.
*<span style="background-color:yellow">If the device isn't completely dead</span>, 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.
*<span style="background-color:yellow">The most powerful  approaches</span> if you get stuck are <span style="background-color:yellow">Internet searches, this Wiki</span>, and <span style="background-color:yellow">discussing a problem</span> 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.
*<span style="background-color:yellow">Harness your curiosity</span>. 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==
==Mechanical Skills==


=== To start with ===
=== To start with ===
You will need a few screwdrivers. The one from the kitchen drawer that was your grandfather's might do, but a set of flat and cross-head screwdrivers in 2 or 3 sizes would be so much better.
<span style="background-color:yellow">You will need a few screwdrivers</span>. The one from the kitchen drawer that was your grandfather's 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.
You know which way to turn a screw? "Righty tighty, lefty loosey" is the easy way to remember.
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=== Gaining your screw-driving licence ===
=== Gaining your screw-driving licence ===
Using a screwdriver is easy, but a few simple tips are well worth bearing in mind:
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.
*<span style="background-color:yellow">Before starting</span> to take the device apart, <span style="background-color:yellow">take a good look</span> 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.
* <span style="background-color:yellow">Choose a screwdriver that's a good fit</span> 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.
*If you <span style="background-color:yellow">feel the screwdriver starting to slip</span> 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? ===
=== ... 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.
So, you've undone all the screws and you still can't get inside. Often, there's <span style="background-color:yellow">one more screw</span> 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".
<span style="background-color:yellow">If it doesn't come apart easily</span>, search online for the device make and model, appending the keyword "disassembly".


==Electrical Skills - Battery Items==
==Electrical Skills - Battery Items==
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===Safety===
===Safety===
Just two things to be aware of (take advice if you're not sure what to do):
Just two things to be aware of (take advice if you're not sure what to do):
*Take care with those [[Compact_cameras|cameras]] and flashguns in which the flash consists of a glass tube. These contain a [[Glossary:Capacitor|capacitor]] which may retain sufficient electrical charge to give you a nasty shock, long after the item is switched off.
*Take care with those <span style="background-color:orange">[[Compact_cameras|cameras]] and flashguns</span> in which the flash consists of a glass tube. These contain a [[Glossary:Capacitor|capacitor]] which may retain sufficient electrical charge to give you a nasty shock, long after the item is switched off.
*Treat [[Batteries#Rechargeable_lithium_batteries|lithium batteries]] with respect. Shorting the terminals together or physical abuse can create a serious fire hazard.
*Treat <span style="background-color:orange">[[Batteries#Rechargeable_lithium_batteries|lithium batteries]]</span> 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.
Otherwise, you can safely work on virtually all items powered by a battery or small solar cell.


===Rock-bottom theory===
===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:
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:
*[[Glossary:Electricity|Electricity]] can only flow if it can flow all the way around a [[Glossary:Circuit|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".
*<span style="background-color:yellow">[[Glossary:Electricity|Electricity]] can only flow</span> if it can flow <span style="background-color:yellow">all the way around a [[Glossary:Circuit|circuit]]</span>, 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 [[Glossary:Conductor|conductors]].) Electricity cannot flow through most other materials (known as [[Glossary:Insulator|insulators]]) such as plastics, rubber, wood, glass, provided they're dry.
* Electricity generally <span style="background-color:yellow">flows easily</span> through <span style="background-color:yellow">metals</span> and to some extent through water or anything damp. (These are called [[Glossary:Conductor|conductors]].) Electricity cannot flow through most other materials (known as [[Glossary:Insulator|insulators]]) such as plastics, rubber, wood, glass, provided they're dry.
*[[Glossary:Volt|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.
*<span style="background-color:yellow">[[Glossary:Volt|Voltage]]</span> (measured in volts) is a measure of <span style="background-color:yellow">electrical pressure</span>, 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.
*[[Glossary:Amp|Amps]] are a measure of the amount of current flowing through a circuit.
*<span style="background-color:yellow">[[Glossary:Amp|Amps]]</span> are a measure of the <span style="background-color:yellow">amount of current</span> flowing through a circuit.


=== Rock-bottom practical===
=== Rock-bottom practical===
*If two wires touch which shouldn't, or a wire touches part of a metal case, this creates a "[[Glossary:Short_circuit|short circuit]]", offering very little [[Glossary:Resistance|resistance]] to the current. In the worst case, this may create a fire hazard.
*If two wires touch which shouldn't, or a wire touches part of a metal case, this creates a "<span style="background-color:yellow">[[Glossary:Short_circuit|short circuit]]</span>", offering very little [[Glossary:Resistance|resistance]] to the current. In the worst case, this may create a <span style="background-color:orange">fire hazard</span>.
*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.
*An item may stop working or work unreliably if there are <span style="background-color:yellow">loose connections</span>, dirt or corrosion on the contacts in a plug or socket, or in a battery compartment.
*A simple [[Glossary:Multimeter|multimeter]] is quite cheap and it's not hard to [[How_to_use_a_multimeter|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 [[Glossary:Fuse|fuse]] and to check for a weak or dead battery.
*<span style="background-color:yellow">A simple [[Glossary:Multimeter|multimeter]]</span> is quite cheap and it's not hard to [[How_to_use_a_multimeter|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 [[Glossary:Fuse|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 [[Basic electronic components#Fault-finding_and_Repair_3|swollen electrolytic capacitors]] and how to [[How_to_use_a_multimeter#Diode and Transistor testing|test rectifier diodes]].
* Faults may be indicated by <span style="background-color:yellow">signs of overheating</span>, such as discolouration or charring on components or a circuit board. Also, learn to recognise <span style="background-color:yellow">[[Basic electronic components#Fault-finding_and_Repair_3|swollen electrolytic capacitors]]</span> and how to <span style="background-color:yellow">[[How_to_use_a_multimeter#Diode and Transistor testing|test rectifier diodes]]</span>.


==Electrical Skills - Mains Items ==
==Electrical Skills - Mains Items ==
Line 74: Line 74:


=== Electrical Practice ===
=== 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.
*Mains leads consist of 2 or 3 wires. The <span style="background-color:yellow">brown wire</span> is the Live and is the most dangerous. The <span style="background-color:yellow">blue wire</span> is Neutral and carries the current back to the mains plug. The <span style="background-color:yellow">green and yellow striped wire</span> (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.
* The 2 or 3 wires are <span style="background-color:yellow">individually insulated</span>, and are all enclosed in an <span style="background-color:yellow">outer insulated sheath</span>. 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.
*When making a connection such as wiring a plug, make sure you <span style="background-color:yellow">cut back</span> the inner insulation from the wire <span style="background-color:yellow">sufficiently far, but no further</span>.
*Any wire that could possibly be pulled, the outer sheath must be clamped to prevent any strain being put on the electrical connections.
*Any wire that could possibly be pulled, the outer sheath <span style="background-color:yellow">must be clamped</span> to prevent any strain being put on the electrical connections.


=== In the real world ===
=== 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 flow of electricity <span style="background-color:yellow">always meets some resistance</span>, which absorbs energy. According to the device, this energy might be turned into <span style="background-color:yellow">physical motion, light, heat</span>, or it might be used to <span style="background-color:yellow">process information</span> 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.
*A <span style="background-color:yellow">loose connection</span> may have significant resistance, and if the current flow is heavy, this may cause <span style="background-color:orange">dangerous overheating</span>. Screw terminals and all other connections <span style="background-color:yellow">must be tight</span>. 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.
*PVC insulating tape <span style="background-color:orange">must never</span> be used as the principal means of insulating an exposed wire or connection.
*A [[Glossary:PAT_Test|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_testing|PAT test]] is not complete without a visual inspection as well, which in practice, reveals the majority of faults.
*A <span style="background-color:yellow">[[Glossary:PAT_Test|PAT test]]</span> 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_testing|PAT test]] is not complete without a visual inspection as well, which in practice, reveals the majority of faults.


=== A milligram of theory ===
=== A milligram of theory ===
*The power of a device is measured in [[Glossary:Watt|Watts]] (W) or kilowatts (KW). 1kW = 1,000W.
*The <span style="background-color:yellow">power</span> of a device is measured in <span style="background-color:yellow">[[Glossary:Watt|Watts]]</span> (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 [[Glossary:Fuse|Fuse]] rating must equal or exceed the Amps drawn by a device.
*Power is equal to <span style="background-color:yellow">Volts multiplied by Amps</span>. Alternatively, you can calculate the Amps by dividing the Watts by the Volts (normally 240V). A [[Glossary:Fuse|Fuse]] rating must equal or exceed the Amps drawn by a device.


[[Category:Fixing]]
[[Category:Fixing]]

Revision as of 16:10, 12 July 2022

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

Warning03.png
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 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 the kitchen drawer that was your grandfather's 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.

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.

A milligram of theory

  • 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.