PROTECT YOUR FILAMENT

Radio Record, Volume I, Issue 48, 15 June 1928, Page 13

PROTECT YOUR FILAMENT

a1 eae AN EASILY-MADE FUSE AXSY listener running a valve set should insert a delicate fuse: of some kind in the B battery circuit in order to protect valve filaments in case of an accidental wrong:connection or short-circuit. By placing one such fuse in the negative lead of the B battery, close to thes battery terminal, all yalye filaments in the set will be pro- } tected, as the fine fuse will "blow" before the high voltage has time to dam-~ age the filament. QccH fuses have been frequently described in this column in connection with eliminators and other apparatus. Over three years ago the writer accidentally dropped a wire and "blew" three valves costing about £2 each, and the tinfoil fuse was devised in order to prevent the recurrence of such a calamity. HIE construction of these fuses is an extremely simple matter, and it is a far better proposition to construct one and place it in position than to bemoan the loss of one or more valves and purchase others for their replacement. . IGARETTE tinfoil is the only essential material required, aud from this dre to be cut the finest pos- sible shreds about an inch long, 4 sharp pair of scissors being used. To make the euting easier, the tinfoil may first be pasted to a sheet of paper,

THE next requirement is a slip of ebonite about idin. long and 3-5 or din. wide. Two 1-8in. holes are drilled in this about an inch apart, and into each hole a brass bolt and washer are placed. A piece of fuse is then put into place with an end under each washer, the connecting. wires to battery and set being placed over the back of the bolts and the whole seeured by a nut on each. An active length of fuse of 4 to jin. is quite sufficient, and uneven cutting does not matter, as if there is a weak (narrow) place in the fuse, so much the better, as it will be more delicate and fuse more readily. Par those who do not enrve to econ-

struct, there is now on the market a Philips H.T, fuse of the "wander-plug" type which answers the purpose mentioned above. | (End of construction)