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DEE3052 EQUIPMENT REPAIR
Transcript of DEE3052 EQUIPMENT REPAIR
SYLLABUS AND SYNOPSIS
ELECTRONIC EQUIPMENT REPAIR provides the knowledge and skills on troubleshooting and repairing the electronics equipment.
This course focuses on the identification of faults in audio amplifier, regulated dc power supply, radio CD player, colour TV receiver and domestic electronic appliances.
This course also provides knowledge and skills on troubleshooting and repairing the electronic laboratory equipment.
PROVIDE A REPORT AND PRESENTATION SLIDESHOW ON THE LEVEL OF SAFETY AND THE PROPOSED IMPROVEMENTS FOR THE FOLLOWING AREAS (ATTACH PHOTOGRAPHS IF APPLICABLE).
1. LECTURE ROOM
2. ELECTRICAL LABORATORY
3. NEAR POLYTECHNIC (PARKING LOT FOR MOTOCYCLE)
4. LIVING QUARTERS (HOSTEL)
5. TREATMENT ROOM (IN CLINIC)
6. CHEMISTRY LAB
7. STORE IN WORKPLACE (POLYTECHNIC)
9. FRONT COUNTER/ RECEPTION
REPORT: MIN 20 Pages
Font : Verdana
Spacing : 1.5 space
Submission due date: Friday, 3rd July 2015
1.1.1 Safety and Laboratory procedure
1. Makmal dan bilik persediaan ialah kawasan larangan. Tidak sesiapapun dibenarkan masuk tanpa kebenaran guru.
2. Peralatan sains, bahan kimia dan bahan biologi dalam makmal tidak boleh dibawa keluar tanpa kebenaran guru.
3. Peralatan sains, bahan kimia atau bahan biologi hanya boleh digunakan atas arahan dan panduan guru.
4. Semua peralatan sains, bahan kimia atau bahan biologi yang telah digunakan hendaklah dikembalikan ke tempat asalnya.
5. Semua radas hendaklah dibersihkan sebelum dan selepas digunakan.
6. Eksperimen tidak boleh dilakukan tanpa pengetahuan dan kebenaran guru.
7. Setiap kerosakan, pecahan atau hal kemalangan perlulah dilaporkan dengan segera kepada guru atau pun kakitangan makmal.
1.0 HAND TOOLS AND SOLDERING TECHNIQUE
Safety and laboratory procedure, hand tools that are used in troubleshoot and repair activities. Types of soldering tools and desoldering tools, soldering technique, good and bad soldering, type of bad soldering.
2.0 TESTING EQUIPMENT
Analogue and digital multimeter, oscilloscope,
AF/RF signal generator, transistor tester and colour TV test pattern generator.
3.0 DIAGNOGSIS TECHNIQUE
Process of disassemble and assemble electronic equipment during repair activities. Faults analyzing techniques: visual techniques, injection and tracing techniques, voltages and resistances measurement technique. Testing and identifying the terminals of a passive and active component using test equipment and data sheet.
4.0 POWER SUPPLY
Function of power supply block diagram, power supply circuit diagram, fault in power supply circuit and troubleshoot DC power supply unit.
5.0 AUDIO AMPLIFIER
Principle, operation and troubleshoot of simple audio amplifier.
Principle and troubleshoot of PA system.
6.0 DOMESTIC ELECTRONICS APPLIANCES
Basic principle of radio and colour tv receiver: block diagram and function of each block, schematic diagram, identify every stage, signal tracing and injecting techniques, DC voltage and resistances measurement at given test point of radio CD player and colour TV receiver and faulty components replacement.
7.0 ELECTRONIC LABORATORY EQUIPMENTS
Basic principle of audio generator and RF generator: block diagram and function of each block, schematic diagram, signal tracing and injecting technique, DC voltages and resistances measurement at given test point and faulty components replacement.
The student will be divided into 2 group; for N002 and N108.
N108: Min 6 lab, N002: Project
Student must follow lab rules and regulation
Suatu Akta memastikan keselamatan, kesihatan dan kebajikan orang-orang yang sedang bekerja, bagi melindungi orang lain terhadap risiko kepada keselamatan atau kesihatan berkaitan dengan aktiviti orang-orang yang sedang bekerja, untuk menubuhkan Majlis Negara bagi Keselamatan dan Kesihatan Pekerjaan, dan bagi perkara yang berkaitan dengannya.
8. Dilarang bermain-main dengan segala peralatan dan kelengkapan di dalam makmal.
9. Tidak dibenarkan berpindah dari tempat duduk yang dikhaskan ke tempat lain tanpa kebenaran guru.
10. Kerusi makmal hendaklah diatur dengan kemas. Keadaan dalam makmal hendaklah bersih dan kemas selepas tiap-tiap waktu makmal.
11. Kertas tidak boleh digunakan untuk menghidupkan api penunu bunsen.
12. Kayu mancis dan benda-benda lain yang masih berbara mesti dipadamkan sebelum dibuang ke dalam tong sampah.
13. Kayu mancis, kertas turas ataupun sebarang sampah dalam bentuk pepejal tidak boleh dibuang ke dalam ataupun ke bawah sink, tetapi mesti dibuang ke dalam tong sampah yang disediakan.
14. Makanan dan minuman tidak dibenarkan dibawa masuk ke dalam bilik makmal.
15. Beg pelajar tidak dibenarkan dibawa masuk ke dalam bilik makmal.
16. Air pili di dalam makmal tidak boleh diminum.
17. Tidak dibenarkan menggunakan peti pertolongan cemas tanpa pengetahuan guru.
18. Langkah-langkah keselamatan mersti dipatuhi setiap masa.
1.1.2 Hand Tools
a tool held in the hand and operated without electricity or other power.
a. Long Nose Pliers
Consist of long, narrow tapered jaws. the jaws may be smooth or they may have serrations for improved gripping. this tools works well in confined areas where the finger accessibility is limited, for holding wires or positioning small parts. they will not withstand severe gripping or twisting forces. long nose pliers are often used in PCB assembly, to set bend allowance of components, and to assiste in component insertion.
b. Side Cutter
Used to remove the excess wire length along the accumulation of solder that usually builds up on the wire after a soldering operation. The size of the diagonal cutter determines the AWG gauge that it will be capable of cutting. Typically a 4 inch (10cm) diagonal cutter will cut a wire such as AWG 24 and smaller. Diagonal cutter should not be used as strippers as they may weak / break the conductor in the insulation. its is a good safe practice when cutting to point the conductor end downward to the floor to prevent the flying conductor ends from causing eye injury.
Tweezers are tools used for picking up objects too small to be easily handled with the human hands. They are probably derived from tongs, pincers, or scissors-like pliers used to grab or hold hot objects. In a scientific or medical context they are normally referred to as forceps.Tweezers come in a variety of tip shapes and sizes. Blunt tip tweezers have a rounded end which can be used when a pointed object may get entangled, when manipulating cotton swabs, for example. Flat tip tweezers, have an angled tip which may be used for removing splinters. Some tweezers have a long needle-like tip which may be useful for reaching into small crevices.
d. Wire Stripper
Used to remove insulation from wire, to prepare the wire for electrical connection during assembly or service of electrical equipment. the most popular wire stripper is the 'Miller Stripper'. This stripper contains a single slot adjustment within the handle to allow for different gauge of wire.
To minimize the damage to conductors, be sure to set the tool for the proper gauge wire, and hold it perpendicular to the wire when pulling off the insulation. Do not use this stripper as a wire cutter, as it will put the cutting edges out of alignment, making the stripper useless.
The most common tools used for securing various stylrs of screws used on electrical/ electronic equipment. they are available in a wide variety of handles, shank lenghts, shapes and driver styles.
Handles: Hardwood or plastic - may have a rubber grip for electrical protection, positive gripping and comfort or large flute to improved gripping.
Shank: a tempered steel alloy that can withstand the distortion caused by the torque during normal use. the shank may have either a round or square cross section. Shank lengths vary from about 8 cm to 40 cm. For general electronic assembly and repair, shank lengths of 25cm is used.
Driver: available for all screw head configurations. Most common style used in electronics are the standard (blade), Philips and Hexagonal (Allen)
1.2.1 Type and Function of Soldering Tools
A soldering iron is a hand tool used in soldering. It supplies heat to melt solder so that it can flow into the joint between two workpieces.
A soldering iron is composed of a heated metal tip and an insulated handle. Heating is often achieved electrically, by passing an electric current through a resistive heating element.
Soldering irons are most often used for installation, repairs, and limited production work in electronics assembly.
There is no proper soldering iron temperature just for a given type of solder - the iron temperature should be set for both the component and the solder. When soldering surface mount components, a small tip and 600F (315C) should be sufficient to quickly solder the joint well without overheating the component.
b. Solder Wick
Desoldering braid, also known as desoldering wick or solder wick, is finely braided 18 to 42 AWG copper wire coated with rosin flux, usually supplied on a roll.
The end of a length of braid is placed over the soldered connections of a component being removed. The connections are heated with a soldering iron until the solder melts and is wicked into the braid by capillary action. The braid is removed while the solder is still molten, its used section cut off and discarded when cool.
A soldering gun is an approximately pistol-shaped, electrically powered tool for soldering metals using tin-based solder to achieve a strong mechanical bond with good electrical contact. The tool has a trigger-style switch so it can be easily operated with one hand. The body of the tool contains a transformer with a primary winding connected to mains electricity when the trigger is pressed, and a single-turn secondary winding of thick copper with very low resistance. A soldering tip, made of a loop of thinner copper wire, is secured to the end of the transformer secondary by screws, completing the secondary circuit. Since the tip has a much higher resistance than the rest of the tubular copper winding, the tip gets very hot while the remainder of the secondary warms up.
b. Soldering Gun
1.2 Soldering Technique and Tools
a. Soldering Iron
1.2.2 Heating power of soldering tools
1.2.3 Desoldering tools
a. Solder Sucker / Desoldering Pump
A desoldering pump, also known as a solder sucker, is a manually-operated device which is used to remove solder from a printed circuit board.
1.3 Soldering Technique
a) Preparing a solder
HAND TOOLS AND SOLDERING TECHNIQUE
The choice of solder is also important. There several kinds of solder available but only a few are suitable for electronics work. Most importantly, you will only use rosin core solder. Acid core solder is common in hardware stores and home improvement stores, but meant for soldering copper plumbing pipes and not electronic circuits. If acid core solder is used on electronics, the acid will destroy the traces on the printed circuit board and damage the component leads.
An alloy of 60/40 (60% tin, 40% lead) is used for most electronics work. These days, several lead-free solders are available as well. Kester "44" Rosin Core solder has been a staple of electronics for many years and continues to be available.
Tinning The Soldering Tip
Before use, a new soldering tip, or one that is very dirty, must be tinned. "Tinning" is the process of coating a soldering tip with a thin coat of solder. This aids in heat transfer between the tip and the component you are soldering, and also gives the solder a base from which to flow from.
Step 1: Warm Up The Iron
Warm up the soldering iron or gun thoroughly. Make sure that it has fully come to temperature because you are about to melt a lot of solder on it. This is especially important if the iron is new because it may have been packed with some kind of coating to prevent corrosion.
Step 2: Prepare A Little Space
While the soldering iron is warming up, prepare a little space to work. Moisten a little sponge and place it in the base of your soldering iron stand or in a dish close by. Lay down a piece of cardboard in case you drip solder (you probably will) and make sure you have room to work comfortably.
Step 3: Thoroughly Coat The Tip In Solder
Thoroughly coat the soldering tip in solder. It is very important to cover the entire tip. You will use a considerable amount of solder during this process and it will drip, so be ready. If you leave any part of the tip uncovered it will tend to collect flux residue and will not conduct heat very well, so run the solder up and down the tip and completely around it to totally cover it in molten solder.
Step 4: Clean The Soldering Tip
After you are certain that the tip is totally coated in solder, wipe the tip off on the wet sponge to remove all the flux residue. Do this immediately so there is no time for the flux to dry out and solidify.
b) Soldering A Printed Circuit Board (PCB)
Soldering components onto a PCB involves preparing the surface, placing the components, and then soldering the joint.
Step 1: Surface Preparation:
A clean surface is very important if you want a strong, low resistance solder joint. All surfaces to be soldered should be cleaned well.
Once you have cleaned the board down to shiny copper you can use a solvent such as acetone to clean any bits of the cleaning pad that may remain and to remove chemical contamination from the surface of the board.
A few blasts with compressed air will dry out the board and remove any junk that may have built up in the holes.
Step 2: Component Placement
After the component and board have been cleaned, you are ready to place the components onto the board. Solder a few components at a time before turning the board over and placing more. In general it is best to start with the smallest and flattest components (resistors, ICs, signal diodes, etc.) and then work up to the larger components (capacitors, power transistors, transformers) after the small parts are done.
Step 3: Apply Heat
Apply a very small amount of solder to the tip of the iron. To heat the joint you will lay the tip of the iron so that it rests against both the component lead and the board. It is critical that you heat the lead and the board, otherwise the solder will simply pool and refuse to stick to the unheated item. The small amount of solder you applied to the tip before heating the joint will help make contact between the board and the lead. It normally takes a second or two to get the joint hot enough to solder, but larger components and thicker pads/traces will absorb more heat and can increase this time.
If you see the area under the pad starting to bubble, stop heating and remove the soldering iron because you are overheating the pad. Let it cool, then carefully heat it again for much less time.
Step 4: Apply Solder To The Joint
Once the component lead and solder pad has heated up, you are ready to apply solder. Touch the tip of the strand of solder to the component lead and solder pad, but not the tip of the iron. If everything is hot enough, the solder should flow freely around the lead and pad. You will see the flux melt liquify as well, bubble around the joint (this is part of its cleaning action), flow out and release smoke. Continue to add solder to the joint until the pad is completely coated and the solder forms a small mound with slightly concave sides. If it starts to ball up, you have used too much solder or the pad on the board is not hot enough.
Once the surface of the pad is completely coated, you can stop adding solder and remove the soldering iron (in that order). Don't move the joint for a few seconds as the solder needs time to cool. If you do move the joint, you will get what's called a "cold joint". This is recognized by it's characteristic dull and grainy appearance. Many cold joints can be fixed by reheating and applying a small amount of solder, then being allowed to cool without being disturbed.
Step 5: Inspect The Joint and Cleanup
Once the joint is made you should inspect it. Check for cold joints (described a little above and at length below), shorts with adjacent pads or poor flow. If the joint checks out, move on to the next. To trim the lead, use a small set of side cutters and cut at the top of the solder joint.
a) Good Solder
The Ideal Solder Joint
The ideal solder joint for through-hole components should resemble the diagram below.
A 'Cold Joint' is one where the solder did not melt completely. It is often characterized by a rough or lumpy surface. Cold joints are unreliable. The solder bond will be poor and the cracks may develop in the joint over time.
Repair: Cold joints can usually be repaired by simply re-heating the joint with a hot iron until the solder flows.
Prevention: A properly pre-heated soldering iron with sufficient power will help prevent cold joints.
b) Bad Solder
i. Cold Joint
At the other extreme, we have the overheated joint. The solder has not yet flowed well and the residue of burnt flux will make fixing this joint difficult.
Repair: An overheated joint can usually be repaired after cleaning. Careful scraping with the tip of a knife, or little isopropyl alcohol & a toothbrush will remove the burnt flux.
Prevention: A clean, hot soldering iron, proper preparation and cleaning of the joint will help prevent overheated joints.
ii. Overheated Joint
iii. Insufficient Wetting (Pad)
These two joints both show signs of insufficient wetting of the solder pad. The solder has wetted the leads nicely, but it has not formed a good bond with the pad. This can be caused by a dirty circuit board, or by failing to apply heat to the pad as well as the pin.
Repair: This condition can usually be repaired by placing the tip of the hot iron at the base of the joint until the solder flows to cover the pad.
Prevention: Cleaning the board and even heating of both the pad and the pin will prevent this problem.
iv. Solder Starved
A solder starved joint simply does not have enough solder. It may make good electrical contact, but it is hard to verify by inspection. In any case, it is not a strong joint and may develop stress cracks and fail over time.
Repair: Re-heat the joint and add more solder to make a good strong joint.
v. Solder Bridge
The left two solder joints have melted together, forming an unintended connection between the two.
Repair: Sometimes the excess solder can be drawn off by dragging the tip of a hot iron between the two solder joints. If there is too much solder, a solder sucker or solder wick can help get rid of the excess.
vi. Lifted Pad
This photo shows a solder pad that has become detached from the surface of the circuit board. This most often occurs when trying to de-solder components from the board. But it can result simply from overworking the joint to the point where the adhesive bond between copper and the board is destroyed.
1. QUIZ ( 4 )
2. EOC (1)
3. LAB (MIN 6 + PROJECT)
4. ESSAY (1)
5. THEORY TEST (1)
LILY YUZIE BINTI MD YUSOF