When Your Set Stops Look for the Cause Don't Go Without Music

Radio Record, Volume IV, Issue 23, 19 December 1930, Page 9

When Your Set Stops Look for the Cause Don't Go Without Music

A Synopsis of what Colin’ W. Smith told 2YA Listeners

LTHOUGH the title of my. talk may sound somewhat foreboding, I .would like to assure listeners right from the onset that I am not going into technicalities. I know perfectly well that grid-leaks and by-pass condensers and oscillations and regeneration are frightfully confusing to the average listener’ who wants merely to turn a switch and listen-in. But although radio is so simple there are yet many things that can go wrong, and the listener himself can attend to without calling in a service man. The natural starting-point for such a discussion is when the set does not start when it is turned on. Now there are very many different classes of "silences," as we might term the fault, and you must first determine which kind it is. If there is no light behind the dial and no humming in the speaker, the electricity is not getting to your set. Turn on your light switch, and if your lamps do not light you will know the trouble is notin your radio, If they do, then one of two things has happened-either your fuse has been blown out, or something is not making contact. To test if it is the fusefit some other electrical device into the socket and see if it goes. In this manner you can soon find out if the trouble is readily apparent. Now we will suppose that the dial light showed when the set was switched on, but there was no hum or live sound. This means that either one of your valves has gone, or that the rectifying valve is not functioning. The rectifying valve is the one which has two plates, and what appears to be two filaments. See if this is lighting, and if it is not it must be replaced. If this is in order, then zvemove the shield from the valves, and see if they are all lighting. If everything appears normal you cannot do very much more than call in a serviceman. Please remember that you must not take on any"thing more than superficial examination yyourself. Listeners: should not attempt to make inside adjustments ‘to their radios, for not only are they likely to get a very severe shock, but the regulations will not allow any unlicensed to interfere with an electric set. You can quite safely touch any metal part of the set when it is in operation, providing all the shields are in position, so do not be afraid to interfere with the aerial or the earth, Many people do not take sufficient eare to see that their aerial and earth are in good condition before contacting a dealer and asking him to examine the set. I know of cases where a dealer has had to go many miles to turn on a switch. . It is the easiest thing in the world to see that aerial and earth are connected and that they are not touching anything they shouldn’t touch,

Much that I have said for the electrie set can be said for the battery set, but the main causes. of trouble are the batteries. They run fiat fairly quickly and although a set may be going reasonably well one night it can refuse to go when turned -on the next just because the batteries are in poor condition. Many will notice that when ‘the battery set is turned on it goes satisfactorily for a while and then drops rapidly. This is because the rest his aiiowed the battery to somewhat recuperate, but it is nevertheless . quite Cone. Another common fault are the connections left off, or put on

wrongly, while the separate speakev is not past giving trouble, Transformers are not as much trouble as they are supposed to be and they are often renewed when they are quite good. If you have a lightning arrester of the cheaper type and have this installed outside, then it can quite easily cause trouble by allowing the water to seep through and cause a bridge between aérial and earth. Weak Signals. "THE next cause of dissatisfaction in a radio set is weakness. In the modern a.ce. set this is usually due FUTTTTTTTT LS LTTEHTT TTL @ TTT PRAT TTT @TTTLTTTETTTTL@ EL TTTTTTTTTT Ee ETTTTTTTTTTT Pm TTT TATE

either to a- fault developing ~in the aerial or the earth systems or. a. defective valve, usually the — screen: grid. This type of valve is a highl) complicated piece of mechanism and. is not without weaknesses. It is not a bad plan to have an extra one on hand and if the set suddenly becomes weak to try it in the position of each of the valves to see if it will improve matters: When vaives have been in operation for about 1500 to 2000 hours, I am speaking now of the modern valve. they begin to weaken and the entire set should be replaced. Now you will be surprised how quickly 2000 hours can run away. Just count up the number of hours you keep your radio set going each week, and I am quite certain you will be surprised. When replacing valves it is not always necessary to use the same make of valves as before. We must all admit that some valves are better than others and it is not a wise plan to buy cheap valves thinking you are getting a good deal. You are not; you are getting a decidedly bad one, for not only do cheap valves have a short life, but they are what we call patchy; that.is, minor defects show up in them and they unbalance the set.‘ Just inquire from your dealer what he considers the best makes before making any replacements. The same is true for the battery set. Almost every year sees the introduction of new valves, that will probably suit your set quite well, and you should inquire either from a dealer or from someone who is conversant with these matters before replacing. Of course there are other causes of weak signals than valves, and I could talk for quite a long time about unbalanced circuits, grid-leaks and’ condensers, transformers, by-pass condensers and such like, for all these can very easily affect the volume of reception, but I know most of my listeners are not interested in such technicalities and I have no intention of stressing them. Anyone who is interested enough to want to delve into his set should drop me a note, I do not want to stress unduly the aerial and the earth because I have said quite enough about that already, but I think most folk will realise that. this can be a very strong factor in deciding whether your signals will be strong or weak. For those who use battery sets, too great a filament voltage is as bad as too little. Distortion, QNE of the most annoying troubles in these refined days is distortion. I mean by distortion that the sounds you réceive are being made very different from the natural sounds. Probably most listeners when they first buy a powerful set wonder why they cannot get the local station well. They find that when they turn the volume down the quality is very ‘poor

indeed. This is to be expected be- ; cause we have not yet a perfect vol--ume control and after it gets past a certain point the incoming wave is * distorted. Endeavour should be made to. work the set with this volume cen"trol on as far as Possible, ,. but. this igs-impossible on the local station, and the easiest way I have found to. get over the trouble is to take the aeriel off, Some sets are made with a switch so that the aerial can be cut off without any difficulty. Please do ‘not imagine that by cutting out at ‘this switch you are properly removing the aerial; You are not, and if. you : take: the’ aerial right away from your

set you will notice a decided drop in the volume. Another interesting point about the volume contro] is that when. q°certain™ point is reached the signals actually become weaker than they were pre-. viously. Do not let this worry ‘you,:as*’ it only indicates that the volume is" at a point where the valves are choked. . There ig another cause of distortion on an a.c. set that is readily under the control of the listener, and that is fail-~ ure to tune to the loudest point. With some stations you can get enough volume without tuning -to the loudest. point, but you are not getting true reproduction like this. The best way is

to furn volume very low and then work the tuning dial, and then, if there is one, the balancing condenser, until the Signal is at its loudest point, then: advance the volume control until the d sired output is obtained. Far too man; people just carelessly tune to a station and Jeave ‘it at‘ that.) These are about the only sources of trouble that .comes to my mind when tilking about a.c. sets. If there is anything else you should consult your service man. Distortion in the Battery Set. With the battery set there are very . "maany .other places where. distortion can take place. There are still a very large number of four and five valve sets whose valres are all alike. This. means they are not using a power valve and consequently cannot receive.true music and speech. Look at your valves and, if they are all the same, then you are not getting the best out of your set. The type of power valve depends on the number of valves in the set, but for five or six valves you want a power valve of the 171A type. I think all manufacturers make this type, so you should have no difiiculty in getting one to suit your conditions.: Smaller sets require a high gain power valve. Of these there are some excellent examples and some amplify the signal as much as do the ordinary valve in your set but they can handle quite a fair volume without distortion. Do not think that a power valve is going.to increase:the loudness of your set. If ahything, it will drop it, but it will better the fone, Just as essential as the power valve is the "C" or grid bias battery. I have mentioned that before and cannot stop now to say anything further about it. If you have a set with four or more valves a bias battery is essential for saving current, increasing the life of your valve, and giving you better tone. The speaker being the last link in the chain‘ between the artist and yourself is often blamed for distortion that is not due to it; but it is frequently responsible for a great deal. Old-fash-ioned speakers, although they might be connected to a good set, cannot give satisfaction, and if you want real qual- ity you must go to the newer types such as the. heavy cones or the dynamics. The horn speaker itself introduces considerable distortion, and it cannot handle much volume without causing trouble. : ‘ There are-other points which could enter into distortion in a battery set. For instance; the detector, if of the grid-leak type, cannot receive very loud signals without. causing trouble. Then again small transformers will not pass the required range of notes, while some of the more selective circuits cut out some of the notes before they get to the detector. But we cannot dwell on these points, and must, before we stop to-night, consider a further cause of trouble. ss Power. Interference, ONE of the most annoying features about any radio set, particularly those used ,in the towns, is the noise pick up. Power lines, tram rails, electric appliances, all. send out waves that the radio set picks up and amplifies. Out in the country farm plants and milking machines are quite capable of spoiling reception. If you know from where. the trouble is coming, arrange to have the aerial at right angles to it and ag far away as possible. You might even get better results by chang-

- ing | your ground connection, by improve ing the ground, by a shorter aerial, or ‘y a counterpoise earth. This latter is ‘nerely another aerial slung a few feet ‘rom the ground and connected with ‘he ground: terminal of-your radio. It -aust in no way come in contact with the true earth, Almost without exception the Post Office inspectors and the power boards are only too willing to help you: to overcome these problems, and they much appreciate it if you can help them in locating the trouble.: If you see a street lamp flashing.on and off or see sparks from any of the insulators on. the ‘power lines. during wet weather you can be fairly well assured that trouble is*coming from them, and if you let the radio inspector know something will be done for you. A little help in this direction is greatly*. appreciated by the authorities. Do noe get power interference and static con fused. Particularly at this time of-the year static is beginning: to make itself a nuisance. . ~