Some factors affecting transmitting valve life

A knowledge of the principles underlying the operation of vacuum tubes enables a user to appreciate what performance may be expected and to understand to what extent factors under his control may influence the life obtained. The object of the paper is to discuss briefly the principal factors which affect valve life, and to do this it is convenient to study the various modes of failure. A number of good operating policies will become evident as the reasons for failure are studied, and these will be stated as the occasionarises. Emission and filament failures in valves with pure tungsten filaments, thoriated tungsten filaments and oxide-coated cathodes are dealt with first. A few remarks are then made about glass failures and operating temperatures. Mechanical failures are mentioned very briefly, and finally certain important factors relating to storage and handling of valves are dealt with.