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Valve/tube, A/R fault

Discussion in 'Electronic Repair' started by N_Cook, Jul 15, 2010.

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  1. N_Cook

    N_Cook Guest

    Well that is what Avo calls it, I've never come across one before. ECC83
    with curious cyclic swirling breaking-surf whitish-noise and clicks.
    Putting on Avo 160 tester showed <>short in A/R setting, I've never had
    before, A/R here stands for cold checking Anodes To Remaining electrodes.
    DVM cold resistance checking pin to pin showed about 9K between an anode and
    its grid. I will replace it but is there any point in blasting with some
    high voltage to vaporize whatever is bridging, for a known
    unreliable/short-term spare. I'm aware that a valve with leaky C to H, then
    running the valve with 10 or 12V on the heaters insted of 6.3V so they glow
    like bulbs for a few seconds, will knock back the bridging deposit for a few
    months or even years.
  2. Meat Plow

    Meat Plow Guest

    Used to do that with a TV CRT rejuvenator. It had a specific function to
    remove shorts. Sometimes worked, sometimes didn't.
  3. N_Cook

    N_Cook Guest

    Same here. I still have it and use it about once every couple of
    years, now on monitors rather than tv crt's.


    Any idea what is causing this A/G resistance? Nothing to loose, I will blast
    it with some volts. But preliminaries I've seriously banged the envelope and
    heated it with hot air and the resistance has hardly moved from 8.7K ohm.
    C/H leakage I've never seen below about 100K IIRC and was highly variable on
    knocking the envelope.
  4. JW

    JW Guest

    Ack! When did Caputo start doing that?
  5. N_Cook

    N_Cook Guest

    60V supply over A-G, dropped the resistance to 4.6K . Tried on a 500V
    Megger, not expecting to do much as only battery powered. Small white flash
    from inside and ohmage shot up to over 200M. Testing on valve tester and
    checks out fine
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