|Radio and Electronics (DED Philippinen, 66 p.)|
|7. COMPONENTS OF MODERN RADIO RECEIVERS|
If you open a modern radio receiver, you will find, that all its components are extremely small. This is because the buyers of those radios want them to be as light as possible and the producers are trying to built them as cheap as possible.
To have light and small radios is on the one hand a big advantage. But on the other hand the tiny components, necessary for such small radios cause three major problems which you have to cope with if you want to repair this kind of radios instead of destroying them:
- small components have also a small mass. Small masses are heated up very easily. Most electronic components unfortunately are easily spoilt if they are heated up to much. Therefore while soldering in such radios you have always to take care,
- that the soldering iron is fitting for the job (as smaller the component, as smaller the iron).
- that the soldering tin is fitting for the job (thin tin takes less time to get molten)
- that you never heat up the soldering point longer than necessary to limit the heat energy flowing to it, or
- if it is not possible to avoid heat, to cool the soldered terminal down by holding it by a pair of plier or touching it thoroughly with a screwdriver.
- small components have mostly very thin terminmalwires too, so you should always be extremly careful when bending or pulling any component in such a radio.
- on an extremly small component you cannot write down any specifications. In order to enable you to find specification even though, there are used special colour codes. Generally you should not rub away any colour or letter on such a component. It might be you need this part of the specifications to repair the device properly.
Inside the radio you will find too that all the components are soldered to one or more sheets of brown or white plastic material which has on one or both sides copper or tinned conductor paths. These sheets are called PRINTED CIRCUITS. These plates are actually the whole wiring of this radio. To make it possible to have a rather complicated whole wiring on these sheets it is often necessary to print the conductorpaths extremly thin. This fact makes it necessary to keep in mind the following:
- Don't bend the printed circuits - you might break a single conductor and you hardly will be able to find this fault anymore.
- heat them up only very carefully - you might destroy the conducting paths and then there is much more to be repaired than before.
- touch the conducting paths only if it is unavoidable-they might oxidate and then give no more good connection.
- if you want to check the circuit, always think about another method before starting to dissolder anything - you might spoil the conducting path.
- if you ever broke a conducting path you can repair it by a piece of wire (insulated or not depends on the case you find) but be careful not do cause a short circuit anywhere by a drop of tin (even a very small drop can cause a lot of trouble). In case of a short circuit you might spoil a few other components.
In order to be able to have a good general view of all electronic components we devide the whole lot into groups. The first of those groups is the group of PASSIVE COMPONENTS.
They are called passive, because they are only reacting on the signal connected to them. They do not control any other value. Examples of those passive components are the resistor, the capacitor, and the inductor. In most of those cases a passive component will have only two wires - but a few of the other groups have two terminals too. The second group of components are the ACTIVE COMPONENTS.
They are called active, because they control currents or voltages on their own, according to orders. Examples of those active components are diodes, transistors and thyristors. Except the diode all of them have more than two terminals.