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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 4th Mar 2013, 4:31 pm   #21
Nicklyons2
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Default Re: Valve Life

Quote:
Originally Posted by Sideband View Post
According to Wikepedia:

'The longest recorded valve life was earned by a Mazda AC/P pentode valve (serial No. 4418) in operation at the BBC's main Northern Ireland transmitter at Lisnagarvey. The valve was in service from 1935 until 1961 and had a recorded life of 232,592 hours. The BBC maintained meticulous records of their valves' lives with periodic returns to their central valve stores.
Rich
Hmm, I think I know where Wikipedia got ther info from; the Mazda Valve Data book 1968. And from my copy, a picture of the 'offending' device - and very fine it looks too. I'm thinking that at the time this record was achieved transistors hadn't been around long enough to equal this record. In fact if my maths is vaguely close the very first transistors would have had to survive until 1974 to equal it.
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Old 5th Mar 2013, 2:22 am   #22
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Default Re: Valve Life

According to a Mazda Ad in the October 1945 WW, their standard SP-41 valve had been selected for use in submarine repeaters because it had been found to be particularly reliable, still being serviceable after 11,000 hours use. This would no doubt have been continuous use at constant temperature, which would have assisted reliability.
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Old 5th Mar 2013, 8:34 am   #23
Radio Wrangler
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Default Re: Valve Life

There certainly was a fear of valve unreliability. Remember how they were treated separately in warranty clauses? 3 months for the bottles and a year for the rest of the set.

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Old 5th Mar 2013, 12:24 pm   #24
HamishBoxer
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Default Re: Valve Life

Over the many years i have done repairs,50 plus years life is nothing for a valve.
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Old 9th Mar 2013, 3:08 pm   #25
Neil Purling
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Default Re: Valve Life

When that Mazda AC/P pentode failed did they actually have a dust-covered spare in the stores?
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Old 9th Mar 2013, 4:06 pm   #26
Nicklyons2
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Default Re: Valve Life

What I know of the BBC in that era would suggest they would indeed have a spare but it wouldn't be dusty! the main transmitters had proper cleaning ladies and canteen staff, the places were spotless. Remember too that many of the transmitters from the pre-WWII era carried on until the frequency changes in the early 1970s (when R1 left 247m and moved to 275/285m).
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