Automation for Quality Control Testing of Electron Tubes

Prior to the mid Forties most electron tubes were production-and quality-tested on an attributes (go-no-go) basis only. Quality-sample sizes were moderate and statistical paper work was at a minimum. Since that time quality-control testing has increased by leaps and bounds under the pressure for high reliability, performance, and uniformity. These factors have increased the quality-control work load to the point where an appreciable portion of the tube manufacturing cost is involved in the quality-control testing and statistical evaluation procedures. In an effort to hold down the rapidly mounting costs of quality testing and data evaluation, to improve operator accuracy, and to reduce the number of tests, a test set has been developed which performs many of the tests automatically. The set provides digital data output for each test on each tube in punched tape, reads out the tape, and prints a copy of the punched data. The punched tape is then fed to a computer which analyzes the data for the entire sample and prints out the answers for those statistical factors such as lot means, standard deviations, per cent deltas, etc., required for the attributes-variables acceptance criteria for lot acceptance. The test set is designed to perform those static and dynamic tests normally performed on a Vacuum-Tube-Bridge test console. It has twenty test positions and will measure and record ten different characteristics on dual section tubes. Provisions are included for manually feeding test data from other equipments into the punched tape for analysis by the computer as desired.