Questions and Answers

Radio Record, 25 March 1938, Page 65

Questions and Answers

H.N. (Parinui): It is quite true "that, by using the 1G5G, the B current will be increased, from 8 ma at 185 volt for the 1D4, ete., to 12 ma, but this valve requires only 90 volt for B supply. As to the comparative costs -the initial cost, which is a running cost spread over the life of the battery, is reduced by one-third and although the current is increased, the running costs are lower. Assume that each block of 45 volt battery costs £1 and that the three blocks at 8 ma drain last for twelve months. B battery running costs are then £8 or 5/- per month. With the two blocks needed by the 1G5G the cost is £2 or 8/4 per month. A: The greater output from the C243N is accounted for by the fact that the B consumption is now 14 ma at 150 volt. Whether this extra output is required or not, is dependent on the type of spéaker and the size of the room-the 350 milliwatt output from the 1G5G seems to be ample for the usual good P.M. speaker and average room.