If asked the question 'how long do the valves last in your radio or television receiver' few listeners, or viewers, would venture an answer. It is also doubtful if many users of commercial radio equipment would commit themselves. Would 30,000 hrs. be too long?
A trial system of multi-channel radio equipment was installed in 1949 between the Marconi works at Chelmsford and a site at Woolwich for the purpose of compiling data on the reliability of equipment, which means primarily the reliability of the valves employed. The system operated continuously for 24 hours each day.
The original valves were removed in 1953, a log having been kept of any replacements required in the interim period. Many of the valves employed are ordinary receiving types found in domestic sets and the data relevant to their performances are given in the table here.
Valves: EF91, EB91, EAC91, ECC91, ECC32, KT66, 5U4G & U52.
This data was originally published in the October, 1957, issue of the Marconi journal, Point to Point Telecommunications.