Use For Old Valves

Radio Record, Volume VIII, Issue 24, 21 December 1934, Page 42

Use For Old Valves

Old valves. that have been discarded because of loss of emission, but are otherwise intact, are very usefui for testing the continuity of wireless circuits after assembly or repair, and they may save a good set of valves if an error in wiring has been made and the "B" supply has got into the filament circuits. The bright emitter

valve of early days will give proof of the continuity or otherwise of the filament wiring-a four-volt valve of this type glows quite brightly on a twovolt supply. Rotation of the filament switch, if it igs of the push-pull type should not affect the brilliance of the filaments, as a flickering glow indicates dirty or loose connections, and

will result in crackling noises when the loudspeaker is connected up. A milliammeter in the plate circuit will indicate continuity, but the readinz given will, of course, be no guide as to what the behaviour of the ‘circuit will be when the new valves are fitted. To save trouble later, the valves when discarded may be marked with a gummed label indicating their type and eharacteristics, as these particulars easily get rubbed off the bulb if it is handled