Tips and Jottings

Radio Record, Volume VII, Issue 7, 25 August 1933, Page 26

Tips and Jottings

[uE simplest and best cure for microphonic howl is to apply "damping" to the glass bulb of the detector valve. This may be accomplished either by covering the bulb completely with sticking plaster, or with a soft lead cap. A. half-inch nut stuck to the bulb with plasticene or chewing gum is also quite fifective. "THD ability to solder joints efficiently is "undoubtedly ‘half the battle in set construction. Certainly it is possible to obtain satisfactory results from the set, with .no soldered joints, but the chances of possible failure or of undesirable noises occurring in the finished set are greatly diminished where soldering ‘has’ beet employed

throughout. After all, there is nothing very difficult about making a soldered connection if the following points are borne in mind. Never attempt to work with tbe iron too hot or too cold, The best indication of the correct temperature is to hold the bit against a piece of paper. It should be sufficiently hot just to scorch it, but not to burn it, With the iron correctly heated, file the end until it is quite clean, and dip it into a tin lid on which has been applied a small amount of fluxite. Then apply a strip of solder to the burnished portion of the bit. The solder should run quite easily and should leave the bit end brightly nickeled in appearance. Next clean the two parts which it is desired to solder, apply a small amount of fluxite, and then, by holding the bit on the prepared parts, the two should weld together quite easily. AN old shaving brush with the bristles trimmed down until they are about an inch in length is an excellent adjunct to the radio worker's outfit. It ean be used for removing traces of flux from a wired up panel, for removing brass steel filings from inaccessible positions, for cleaning soldering irons, and for a variety of other purposes. s * WHEN an ebonite panel is cut, it will be found that the cut edye is very rough in appearance in comparison with the finish of the original edge. To obtdin a similar finish for the new edge, the panel must first of all be clamped in a vice and the marks from the saw removed with a mellum flat file. Work the file diagonally across the edge, taking care not to cut too deeply at any one point. Next lay the file flat along the edge and push it straight along with firm strokes, keeping the whole length of it pressed down on the work. Now wrap @ strip of emery cloth round the file and work with this in straight lines backward and forward until all the file marks have disappeared. Repeat with the finest emery paper. Finally, moisten a piece of rag with turpentine, rub this into the edge, and polish off with a clean, soft rag. Fs % N not a few cases peculiar and very unpleasant "zizzes’" in loudspeakers of the balanced armature type may be traced to actual vibration of the baffle board. Some of these instruments produce in themselves a great deal of vibration, and these vibrations are transmitted to the board. The result is that whenever a note of the natural frequency of the board occurs, resonant effects are observed. One way of overcoming this difficulty is to make a stand for the unit and its cone and to place it behind the baffle so that the front edge of the chassis just clears it.