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Basic Tools
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| Here are some of the tools which are commonly used for satellite receiver repair. The heavy mallet is ideal for bending the wires of components after insertion in the holes. Gas pliers can be used to remove components without the need to de-solder. Use a wrench to undo stubborn tuner nuts, when a spanner is unavailable, and a rasp to smooth the threads. |
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| A heavy duty soldering iron is ideal for use with surface mount components. (Get it nice and hot over a gas burner). A variety of cramps will be needed to secure the board during hammering and soldering operations. Finally, no tool kit would be complete without a glue pot. Absolutely indispensable for fixing those lifted pads and tracks after somebody else messed it up! No, I'm not serious, but some people do actually appear to use these tools when attempting repairs! |
The Proper Tools Before you embark upon any repair or modification work you should have an understanding of the basic use of tools used in electronics.
You really can not do better than to take an electronics course at college, if only to get accustomed to using the tools and terminology used in electronics.
DANGER!
Once you remove the cover screws on a satellite receiver you expose yourself to a real danger of electric shock or burns. The intention of this section is to make you aware of some of the methods by which receivers can be repaired and modified and, while you might be encouraged to "have a go" yourself, please consider the risks involved not only to yourself but to others if you are doing a "favour" for a friend.
Inside the receiver is a section which carries mains voltages. That is the good news. In a receiver which uses a "switch mode power supply" there are even higher voltages present. This power supply is extremely dangerous. Keep your fingers and tools away from it! You will find that it is almost always marked with a warning notice or symbol.
You are recommended to take the receiver to a time-served repair engineer if you are in any doubt at all.
First, you need a set of basic tools. You are definitely not going to be successful if you use hedge cutters for cutting wires and a poker for soldering!
Screwdrivers
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| The most common screwdriver is the flat-blade one used for slot-head screws. People don't seem to realise, however, that this comes in different sizes. Use the one which fits the slot exactly. The blade should be square-ended NOT sharpened to a chisel point or rounded off because you tried to use it on a cross-head screw! Cross-head screwdrivers come in two different types and several sizes. One type is called "Phillips" and the other is called "Pozidriv ". If you use the wrong one it will slip and damage the slots. The two most useful sizes are #1 and #2, although you might also need #0 for very small screws. An unusual type of screwdriver is needed for receivers manufactured by Nokia. It is called a "Torx" driver and has a star shaped end. It is almost impossible to remove Torx head screws with anything other than the correct size Torx driver. The most useful size is a number 10 but some receivers used a number 9. |
Pliers
Pliers come in all shapes and sizes. For handling electronic components you will need a very small pair of needle-nosed pliers. A larger pair of snub-nosed pliers will be useful for holding a nut while you tighten the screw.
Cutters
One of the tools most people think they can do without until complaints arise from your spouse regarding misuse of the kitchen scissors! For cutting leads on components you need very small cutters. However, DO NOT use these for cutting thick cable or fence wire.
Soldering Iron
You can buy a very low-cost soldering iron which will be satisfactory if you seldom use it. Such irons usually take a long time to reach the usable temperature and lose their heat rapidly when used to heat up anything other than the smallest solder joint.
A better choice is a high wattage, thermostatically-controlled iron. The one which I have used for twenty years is rated at 45 Watts and I use a number 8 tip which keeps the temperature above 400 C. The tip is iron-coated and lasts a long time. (Iron-coated tips must not be cleaned with anything other than a damp sponge or the iron will peel off and the tip will be useless). The tip size you choose should be tiny about 1mm.
Solder
You need fine solder of 0.7mm diameter or less for soldering modern electronic components. The solder should contain cores of flux. The percentage of flux will be marked on the solder bobbin. You will see that the solder is a mix of tin and lead in 60/40 proportion and the flux percentage should be about 5%. A higher percentage might make soldering a little easier but leaves a residue on the printed circuit board which looks messy and makes it difficult to inspect your work. A lower percentage may be acceptable and leaves virtually no visible residue but is not recommended for a beginner. (I use 2.2% rosin cored flux class 5A, grade KP, 0.7mm diameter 60/40 tin/lead solder from Maplin).
The reason for having flux is that it melts and flows over the metal which you are soldering. In doing so it excludes air and prevents the metal from oxidising (which would make it impossible for the solder to stick to the metal). Flux also has a slightly acidic action and dissolves any oxidation which is already present.
The most common flux is a resin called "rosin" which comes from trees. However, a number of synthetically manufactured fluxes (such as X32 made by Multicore) are also used. These fluxes leave either less residue or a clear residue, which makes inspection of the solder joint easier and may result in a more reliable circuit, since flux is known to cause problems if left on the board. However, your eventual choice may be influenced by the smell of the flux and its action on your nose and eyes!
Soldering
To remove a suspect or faulty component from a printed circuit board is easy once you know how!
Many people swear by pump-action solder-suckers. These are like miniature bicycle pumps with an internal spring. You prime the sucker by pushing the plunger down until it locks. Pressing a button releases the spring-loaded plunger and it sucks up anything close to its nozzle. Great for zits! Not so great for printed circuits. The usual effect is that it sucks the copper pad right off the board, leaving you with nothing to solder the new component lead to.
By far the best method is to use a product which goes under various names such as "Multicore desolder wick®" or "Desoldering braid". This is very fine braid like the screening braid found inside coaxial cable. The difference is that it is impregnated with flux. Simply place the braid on top of the solder joint and press the tip of the iron onto it. When the braid is hot it will melt the solder which will be drawn up the braid by capillary action, aided by the flux.
Sometimes you will need to "prime" the braid by melting a spot of solder into it called "tinning" just to get it started.
When the solder is gone, use the tip of the iron to heat the component lead and push it upright so that it can be removed easily from the hole.
In the case of "plated through holes", where the copper goes all the way through the circuit board, you must make sure that ALL of the solder has come out of the hole. If it hasn't, resolder the joint with fresh solder then use the desoldering braid again.
Repeat this process for every lead or leg of the component then lift it out of the holes.
To solder a new component in, bend the leads (if necessary) to match the hole centres. Push the leads through the board, taking care not to lift the copper pads off the board. Bend each lead in the direction of the copper track, making sure that the component is flat on the board (unless the original was spaced higher to dissipate heat). Hold the end of the solder on the copper pad and press the tip of the iron onto the solder. Rotate the tip left and right while pressing and feed more solder in as it melts.
Common Soldering Problems
It is easy for an expert to tell when an amateur has attempted a repair! Broken copper pads and tracks are common. Amateurs tend to put too much solder on the joint (and everywhere else, too!) and leave nasty big stains of flux so they can't see the track breaks which they have left.
The solder joint should have a bright, shiny appearance and the component lead should stick out of it and not be submerged. The solder meniscus around the lead should be concave (curved inward) like a volcano. It should not look like a ball. If it does, then the solder has probably not made a good connection to the component lead.
Components should sit flat against the board, or be pushed down as far as they will go. Otherwise, when you touch them, the copper pads to which they are soldered will snap away from their copper tracks to leave an open circuit or an intermittent (on/off) connection. Even if you do not touch the badly mounted component, there is every possibility that vibration or a knock will cause it to move and damage the copper track. The only exception is that a component which may run hot, either normally or under fault conditions, may be required to be spaced away from the board. In such a case, the component legs should be kinked to hold it in place or heat-resistant sleeves or beads should be fitted to the leads. Always copy the mounting method of the original component.
When you bend a component wire underneath the board it should always lie along the attached copper track, if possible never away from the track. This position ensures that, if you need to desolder it, the copper pad will not be damaged.
A common mistake of the amateur is to melt the solder on to the tip of the iron then carry it to the joint. The problem is that the flux has evaporated by the time the solder gets there so a bad joint is inevitable.
Always put the iron tip onto the component lead and copper pad then apply the solder to the opposite side of the pad, forcing the solder on to the component wire and around the copper pad.
Feed in just enough additional solder to encircle the joint then take the tip away immediately. Hold the component still for a few seconds until the solder has solidified.
Movement of the component lead while the solder is still molten will cause a "dry" joint. The solder will be greyish rather than shiny silver and the connection may be no good. If this should happen, remove the solder with braid and re-solder the joint, carefully.
The above text is an extract from "The Repair Manual edition 5" by Martin Pickering The book continues by explaining how to recognise the various types of electronic component, including Surface Mount Devices, and how to solder and desolder them.
Martin Pickering can be contacted for advice about satellite receiver repair via the Internet:
You should first read the Frequently Asked Questions files here before filling out the questionnaire.
Be sure to state make/model of ALL equipment and describe the fault symptoms, history, tests you have made (swapping receiver, LNB etc.) and voltage measurements (LNB voltage). Technical advice can not be given by telephone.
HOW DO I PLACE AN ORDER?
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Version 1.1 updated on 3/5/99
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