Show excess load on tubes Is not good judgment it la Is unfortunate in a way that vacuum tubes are very much like faithful horses in performing the he duties imposed upon them tubes like horses will work and strain at tasks that should never have been im posed upon them they cri crack it under the strain according to roger koger at AL wise radio engineer e ligi neer tile the failure to realize that adjustment by ear of tile alie voltages furnished by U B power devices almost invariably results la in the use of excessive plate voltage to la frequently responsible for dissatisfaction ow on tile the part of the listener at tile lie service obtained from the tube tills this Is id particularly ua birly true of power powei tubes with which reception as judged by the ear car improves as the tube la overloaded as regards plate pi voltage A complete discussion of the prop er plate and grid latt cry voltages to use usa for every type of of tube la Is too lengthy to be taken up in this article but 0 few general hints will prove of oi value complete specifications aud and operating characteristics of tubes are given in the sheet of instructions regarding reg it arding their proper use which tube manufacturers supply in n the lie cartons in ID which their tubes are puked these specifications ficat ions regarding the proper filament voltage plate voltage and grid bins bias to use with such tubes and tile the uses to which the tubes can be put pill should lie be studied carefully before th the e set Is designed and wired so that full ad vantage can be taken of the knowledge gained by tile the manufacturers in the experimental and development work which tins been done with the tubes As A s a concrete instance it might be inela mentioned tinned that with a grid bias of 40 volts bolts the normal plate current drawn drain by a type power tube at volts Is 20 milliam milliamperes beres whereas with alib no grid bias the plate current may jun j un run ag as high us its milliamperes dissipating so routh much heat in the me tube that the tolate plate of the tube will be heated io to redness with all the e growing popularity of battery eliminators the tendency teti dency has ha s grown to adjust tile the voltages supplied to the receiver by such units entirely by ear since these and the conditions under which they are used vary greatly it Is almost impo sible to io determine the correct settings merely by listening to the receiver and adjusting the unit until reception souis bouis all right i 1 the variable adjustments of these should ae be s set t accor accurately t to the receiver with which they anre used a high resistance voltmeter being e ean w aloyed for tile the purpose when once adjusted they should be left severely clone alone unless a change in tallor tuba types are made this adjustment should preferably be made by a a radio radii service man who is properly improperly equipped with instruments to make the necea sary tests the man who installs the eliminator Is the logical man to adjust it to the set nothing less than a reading of the voltage delivered dell vered at each tall ap should he be abc acc accepted e apted as a sat Is factory test on hi part |