Radio today (Jan-Mar 1939)

SERVICING FOR PROFITS (Continued from page 35) filings is to use a piece of ordinary adhesive or scotch electrical tape which may be pushed into the gap with a piece of wire or centering shim. Third: The correct position is such that the voice coil extends an equal amount on either side of the upper pole piece. This may be determined by eye since this may be done with sufficient accuracy. Fourth: If a spacing ring is necessary it should be cemented to the speaker first applying a coat of radio cement to both surfaces. The upper spacing ring may be applied at this time. Fifth: After the cement has set, speaker centering shims should be used to properly center the voice coil. While cementing (step four) the voice coil is centered by eye. Sixth: Tighten spider center screw if the cone is of the type in which the spider is held by one or more screws. Seventh: Remove centering shims. Eighth: Feed a sine wave 60 cycle signal to the voice coil as mentioned before. The output should be absolutely free from frequencies other than the fundamental and the power line frequencies are an exceptionally good source. P.M. dynamics P. M. dynamic speakers require special care in removing any particles of magnetic material from the gap, as in step two above. It is inadvisable to disassemble' the speaker since the magnet will lose some of its magnetism in most cases. Speakers which are badly rusted from out-door operation should be cleaned and remagnetized. Most P. M. speakers made today have an enclosed voice coil assembly. A paper spider having concentric corrugations is cemented to a ring and this must be done at the same time as the rim of the cone is cemented to the speaker. In some cases an inside spider is found on the original speaker. These cones are supplied with an extra spider which replaces the original. It is important that in cases such as these the speaker centering shims must be put in position while cementing in order to properly position the spider. Ample cement should be used to insure a good bond. After testing, the dust button or felt dust cover may be cemented in place. WORDS OF SERVICE MEN HAVE DRAG When a service man is called upon to repair a recently-purchased receiver, it is a foolish idea to make any kind of an unfavorable remark about it, to the owner. This is an important aspect of business procedure, according to Charles Golenpaul of Aerovox, who brought up the matter at a recent RSA meeting. It is well for the service man to remember the endless time, effort and money required of the set manufacturer before the receiver finally reached the consumer. The fact that the instrument requires fixing is bad enough, without the radio man implying that the buyer is stuck with shoddy merchandise. It is much better tactics to compliment the customer on his choice. Service men are likely to make sour cracks about receivers because they want to appear to be expert, because they are sore at some particular set manufacturer, or because they are just careless. But every time they open their mouths in this vein, thousands of dollars worth of radio promotion is abruptly cancelled. The Voder shown in operation actually creates its own speech. MACHINE CREATES TALK Newest development from the Bell Telephone Labs is the Voder, an electronic device which can talk in understandable English, French, German, etc. The device does, however, have a slight electrical accent. Unlike previous devices, the Voder pictured herewith actually creates sound just as the human vocal chords do. The synthesis of speech and other sounds is controlled by the extremely rapid fingering of 23 keys. A foot control gives inflection to the sound. Basically the device consists of a continuous tone generator (saw-tooth oscillator) and a hiss generator together with numerous band pass filters. From the two basic sounds and proper use of the filters (selected by the operator at the keyboard), it is possible to construct any sound. The inflection control changes the pitch Neat and convenient service bench of Radio Sound Service Engineering Co. in Washington, D. C. Note that use of sloping panel and shelf keeps most of the test equipment off the bench, thereby stepping up efficiency. 40 Radio Today