Useful Hints

Radio Record, Volume VI, Issue 51, 30 June 1933, Page 28

Useful Hints

WHEN considering the suitability of a particular type of rectifying valve to the supply the needs of an auc. set, it must not be forgotten that bias voltage will almost certainly be derived from the same source, and that the amount of this voltage must be subtracted from the total rectified voltage output before one can determine how much voltage will be available for the plates of the valves. For instance, a rectifier intended to give J) mils. at 250 volts would hardly do for a receiver taking that amount of current and fitted with an output valve rated at 250 volts maximum. A valve of this type would probably take something like 30 volts grid-bias, and if so, the maximum voltage available for its anode would be somewhere around 220 volts. HANDY light, which will be found especially useful when making adjustments in dark corners, may be

made from a fuse bulb holder, two 4in lengths of stiff copper wire, and two

eroco didle clips, all wired together

as snown in the sketch. This little gadget may be clipped on anywhere on the set, one clip of course going to the A+ circuit, and the other to the A-. OFTEN an earth lead corrodes badly at the point where it enters the ground, owing to electrolytic action. This trouble may be prevented by obtaining a two or three-inch length of brass, lead, or copper tubing, and running the earth lead through at its point of entry intu the ground. Fill the tube up with wax, taking care to see if possible that the earth lead runs centrally through it and does not touch any part of the tube. WHEN installing a multi-wire aerial, it is often a problem to devise a simple but. effective menns of bringing the aerial down leads into one common path. It is not an easy matter to solder two or more multi-strand aerial wires, and, of course, twisting them together will not be satisfactory. A suitable method is as follows :-Obtain a four-inch length of brass tubing of about tin. diameter, flatten one end of it. with a. hammer, and drill through this a hole large enough to ehable the , tube to be screwed to an ordinary lead--in tube. Now bring all the aerial down leat wires together within the brass ‘tube, pushing them down to the bottom. With the wires in position pour : molten lead into the tube until it is full.