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Reliability of valves/tubes - quiz question

Discussion in 'Electronic Repair' started by N_Cook, Oct 1, 2008.

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  1. N_Cook

    N_Cook Guest

    As far as heaters are concerned. I went to a lecture by Tony Sale of
    Colossus rebuild fame
    http://www.codesandciphers.org.uk/lorenz/mk2.htm
    About 2,500 valves in this computer.
    They power up Colossus each day via a motorised variac.

    How many valve failures a year, due to failed heaters in those 2,500, would
    you expect ?
    Please reply here

    Answer tomorrow
     
  2. N_Cook

    N_Cook Guest

    They are all old contemporary valves. I should have said how many failures
    for whatever reason in those 2,500 per year ? considering that they are
    powered up slowly from cold, to reduce that reason for failure .
     
  3. N_Cook

    N_Cook Guest

    In the 40s Colossus was left on 24/7 on the recommendation of Tommy Flowers
    , Dollis Hill engineer, for maximum filament life.

    Answer tomorrow will be what Tony Sale actually experiences in running the
    Bletchley colussus 7 days , only days , a week
     
  4. Arfa Daily

    Arfa Daily Guest

    I seem to recall reading that during the service time of the original
    machine, not a single valve failed. Were they KT66s or 88s ...?

    Arfa
     
  5. N_Cook

    N_Cook Guest

    About 5 valves a year need replacing.

    IIRC about 1,000 of them are thyratrons, 2 are needed for each single bit of
    memory storage. The mark 1 did not have them and required running 2 loops of
    paper tape , the mark 2 required only 1 paper tape loop
     
  6. Guest

    Say, it runs 8 hours a day, every day... That is 2922 hours of operation a
    year. By rough estimate, every 5 years the complete valve supplement will
    be renewed. That is 500 valves a year. When it runs only 4 hours a day, it
    will be half this number, etc.
     
  7. Guest

    I should have consulted both the life expectany figures of the tubes, and
    the rest of the thread before answering too late. Is 5 valves a year a
    long term average?
     
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