ECA TEP194

Abstract

<u>INTRODUCTION</u> <br>Since the advent of commercial television, the picture tube operating anode voltage in TV receivers has been increased from time to time, requiring that more and more X-radiation shielding be provided by the glass envelope of the picture tubes. These periodic changes are delineated by the grouping of JEDEC X-Radiation Limit Curves for monochrome TV picture tubes according to the time periods when tubes were produced from glass manufactured, (1) prior to 1959, (2) between 1959 and 1965, (3) between 1966 and 1969, and (4) beginning in 1970. TV picture tubes are grouped according to the time periods when tubes were produced from glass manufactured, (1) prior to 1970, (2) between 1970 and Similarly , the JEDEC X-Radiation Characteristic Limit Curves for color 1973, and (3) beginning in 1973. <br>Prior to 1970, the glass envelopes used f or TV picture tubes were designed to provide the required attenuation of X-radiation for the normal operating condition of TV receivers and the maximum ratings of the picture tubes. Beginning in 1970, the attenuation was increased to assure that the X-radiation from TV receivers did not exceed the Federal Performance Standard ⁽¹⁾ under abnormal or failure mode operating conditions. Such abnormal conditions often resulted in the picture tube being subjected to anode voltages which exceeded its maximum ratings. <br>In order that the TV set designer could make maximum utilization of the JEDEC X-radiation Limit Curves, these curves were developed for anode voltages well in excess of the maximum anode voltage rating of the picture tubes. curves thus provided picture tube characteristics to the TV set designer for anode voltages nearer to those voltage values actually encountered under failure mode conditions. <br>The JEDEC curves for tubes utilizing glass produced prior to 1970 were developed and published to provide a historical record of the X-radiation characteristics of such tubes as they were originally designed and manufactured and to provide the necessary reference guidelines for developing information for the service industry with regard to the use of replacement tube types. The X-radiation characteristics were not always included in the defining data for tubes types registered with JEDEC prior to 1970. <br>Therefore, when a substitution tube type was required as a replacement in a TV receiver it was not always obvious that the original X-radiation shielding was being maintained. Now, by the use of these curves and JEDEC registration data, reliable picture tube replacement charts for use by the service industry can be published.