Show j r UV e 0 fill 6 A 4 diagram showing tube connected for the th purpose of flashing the filament I 1 by ARTHUR F 8 B in do boston ton herald S many radio fans have no doubt heard about some sort of a process by which inactive tubes may bo be restored to their former activity but according to the lie many questions concerning it there lins has been evidently a shroud of mystery cast over the process some know from observation and many others know through sad experience per peri lence ence that the vacuum tube con faint alna n filament that bec becomes onies luminous when a current passes through it tills this filament receives its current from tile A battery coutray to the popular belief the filament Is not put in the tube for illumination purposes ses but to serve as a source of the electrons necess necessary essaiy dry in III the mechanism allI sIll of the alie vacuum ubo tube A more moie I 1 technical term terin for the filament Is hot cathode cat liode all and simply means that it becomes a source of negatively charged pin particles tides known as electrons elections when it readies reaches the proper tempera ture tuie tills temperature is liy by passing a current through the fili for tills this reason it would per hups be more to the point to cill it ills current the healing instead of tile more coil common linon expression filament current treating filaments tho the first fil were ere of pure tungsten carbon platinum etc hut but it nalls goo koon dc di allt tile number of cle elections drons emitted by the liot hot cathode or nhu nent could bo bior increased by the surface of the filani filament ent with W certain chemical compounds the compo compounds ulla that proved to be the most active in this respect aro are the alkaline earth oxides such its as barium cal calcium chim strontium etc rohwer a still more active material was discovered in recent years gears and Is known as thor thorium litin oxide it inny ile be of interest to know that it Is of the titanium series of elements and Is used in tile lie fornia tion of incandescent agni illan S another vry ry interesting fact is hut it is radio accle because of 0 the lie compounds two general types of filaments have come collie into they flioy being tile lie oxide coated filaments and the thor fil the and 12 nrc are examples of the lie former laile the and tubes tire lire tit in the alie latter class As tile lie oxide coated filament cannot canna be rejuvenated I 1 will not discuss it tiny further in fit tills this article but will focus lily iny attention on tile hor thor style element this type of consists or of a tungsten core that lias has boon been trailed with thor thorium luin oxide not merely coated with the compound but actually impregnated so EO halt the of active wat u material uter erial lal on the surface of the filani ent Is comparatively small tit in comparison ison with willi tile total amount antoun t it Is because of ills his feature that a tube employing employ tug it a filani ent of this variety seldom beldom sees goes ota of service beci decitise tise of a burned out filament ll ament but because the he emission lias has dropped below the necessary value when tills this condition has fins been breathed the tube Is slid to ho be inactive the real of this expression Is that most of hie active material lias has been evaporated d from the eurlace of the filament and ns as a consequence the nui number liber of electrons emitted Is reduced to a very low value now how to flash a tube this process merely consists of burning the filani filament ent by passing a current through it but with the B battery tot totally illy disconnected wit why y should tile the 11 1 battery be disconnect enduring ed during the r n activating lilea measures sues well this Is bica enry because with the B battery connected the post uve ove high voltage charge on the plate would cause the he material to become exhausted ns as fast na as it came to tho the surface pin face which Is at best a very slow rule rate clience it Is necessary that we re above the cause of the exhaustion in it tile lie accompanying di diagram agrain I 1 liae have shown a tube connected for the purpose or of flashing the filament the only connections necessary tire lire tile the two leads front the filament posts of the lie socket connected in series alth a rheostat and a covolt 6 volt Nit battery tery As to the lie time required for lashing flashing I 1 suggest that those who try tills this process to impress the full sit volts across tho filament for abou one minute and then by means of the rheostat reduce the viol voltage tage until the filament burns tit at normal brilliancy then allow ill low the filament to burn for it a period of 12 hours or more it if the lie tube Is still found to be inactive after this treatment it may be for a second or so by connecting a 2212 22 volt tolt B battery to its filament and then cooked for a n longer period at normal brilliancy biancy the same reactivating process may be applied to the tube or any others having a thoi thor type of filament |