Hints for Beginners

Radio Record, Volume VII, Issue 10, 15 September 1933, Page 26

Hints for Beginners

Curing "Chattering": If the best results are to be obtained from a moving coil loudspeaker it is essential that the coil should be free to move without touching the walls of the magnet. If the centring is at fault it can be set right in the following manner. Nearly all moving coil loudspeakers have 2 shall

screw similar to the one marked "A" in the accompanying sketch, which. holds the coil and the cone in position, This should be loosened and the coil moved carefullv from side to

side until the position is round wilere it has equal clearance around its circumference. When the central position has been found, tighten up the screw and notice if there is any improvement. Great care should be taken in handling the cone and coil, as the construction of many speakers is very delicate.

A Lead-in Hint: When 7/22 gauge wire is employed for an aerial, and the lead-in is taken direct to the set, it is usually difficult to connect it satisfactorily to the aerial terminal. Its stiffness prevents it from being easily bent around the terminal shank, while on screwing down the terminal the wire springs away. A very simple solution is to obtain a short piece of fairly thick insulated wire of the flexible variety, bare both ends and attach one to the end of the lead-in, This connection can preferably be made by soldering and then covering with insulating tape. The other end may then easily be looped and firmly fixed under the terminal. The Art of Soldering :Many constructors,

when making soldered connections, simply put together the two parts which are’ to be joined, dab on some flux (usually about ten times as much as necessary) and then hold the iron (heavily crusted with oxide) -against the parts and hope for the best. This procedure is very unlikely to lead to a soldered joint, and, moreover, if the parts are adjacent to ebonite or bakelift, there is considerable danger of the prolonged heating causing danger to these components. The essence of soldering under circumstances like these is to arrange matters so that the hot iron need be. applied only for a very few seconds. This can be done by having the parts properly tinned before they are placed together, and also by having the tip of the iron cleaned and properly tinned also. If the iron has been overheated and has become coated with scales, this should be removed. and if necessary the iron should be filed up with an old coarse file. The two parts to be joined should then be tinned separately. If this is properly done. all that will be necessary to make the join will be to place the two parts to- gether, and apply the iron, with a very small quantity of solder, to the parts. The solder will run within a second or two, and the job is complete.