Show how to obviate shoats when using new tubes A point not previously brought out the shielded grid tube is that if with other receiver tubes a hum Is heard from B eliminator or last audio the shielded grid tube P properly 1 opeil y operated will reduce the bum materially while valle the shielded f grid tube works without a metal shield covering jt include a shield since hum la Is reduce ih the Instance ed at cited above and besides other forms af pf interference avolt fed also ground the shield by connection to either filament post i in id making g ihla his connection remember that when the tube Is used as a 1 radio frequency amplifier it the all clip on th the 0 cap touches the 7 metal shield shiela a sh short orf of the input results no signals are heard beard so if you hear noth noali ing look to this possible cause of trouble when the tube Is used us its a space charge dector with top cap connected to B plus then if 1 the clip and shield touch the 1133 B voltage may be directly applied to the filament and this might ruin the tube so be careful it la Is almost impossible to causi cause such a short without gross carelessness as the shields have hard rubber tion that well protects the two circuits radio world |