Tips and Jottings

Radio Record, Volume III, Issue 23, 20 December 1929, Page 31

Tips and Jottings

Stripping Insulated Wires. WHERE cotton or silk coverings have . to be removed so that tappings can be made, the use of a safety razor blade will be found very convenient. The. blade should be-kept parallel with the wire, or nearly so, to prevent cuting into the conductor.. Any fluff which cannot be cut off may be singed, off with a match or lighted taper. The covering of very smail wires may sometimes be drawn back with the fingers to enable enough wire to be bared.to make a joint or other connection. Rubber covering may often be pulled off after a small incision has been made in it, but should this not be possible a slit may be made in the-rubber, and the insulation pulled back, when it will be found that the insulation will split easily. This maybe continued until enough wire has been bared. © A Substitute for Ebonite. [ft is not generally appreciated by the average wireless experimenter that sulphur is an excellent insulator, rivalled only by porcelain and amber, Among its advantages may’ be mentioned the fact that it does not absorb moisture from the air. In addition, it can be easily melted and*éeast in position and takes a.good polish. Sulphur should have a much wider application than hitherto, one suggestion being for insulating holes when mounting wireless components on a. wooden panel in Heu of ebonite. The main disadvantage of sulphur is that it is not as tough as ebonite. , Defective Grid Leaks. A GRID leak that varies in value will cause an overlap to appear one day which vanishes again on the next, and will make the set oscillate furiously on one occasion and not at all on another, These are, of course, extreme cases, but a "self-variable" grid leak will be a constant source of trouble. Trouble of this sort will not occur if ir es nN SR RSENS

cate is taken to purchase only reliable makes of grid leaks, Another objectionable effect, also caused by a defective grid leak, is a slight tendency of the set to burst into a "howl" just as if is brought up to the oscillation point. If this occurs it: will generally be found that the grid leak value is too high. Diaphragm Protection. VERY. often, horn-type loudspeakers, big and small alike, give bad tone owing to dirt; having collected ‘upon the diaphragm, or to the latter having become rusty. The remedy for this type of trouble is obvious, and it can be prevented from recurring. more or less simply by unscrewing the horn portion of the speaker and gluing a piece of thin but tough paper over the stem. For trial purposes only, the paper may be fasténed down by means of a tightly-fitting rubber band, but, as a permanent fitting, it is: best glued. down. This device entirely prevents dust and dirt from settling upon the diaphragm, and, if any slight diminution in the strength of reception is apparent, it can be removed by pricking a few holes with a needle in the paper cover, In most cases, however, no decrease in the reception of strength will be noticed. A Hand-drill Screwdriver. For rapid screwdriving it is an exe. cellent tip to make a screwdriver attachment to fit one’s hand-drill. This can be done from a short length of }in. ‘steel rod. One end is filed up or ground into the proper shape for a blade and is subsequently tempered by heating and dipping in oil. Box spanners can also be made in the home workshop to fit the hand-drill. ‘Take a piece of brass or mild steel tube whose internal diameter is such that it will just fit tightly over a nut of the size required. Ptit a short piece of studding into the nut and insert it into the end of the tube. Now hammer the outside of the tube near the end, shaping it to fit snugly on to the faces of the nut.