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Listing of bad valve batch numbers anyehere?

Discussion in 'Electronic Repair' started by N_Cook, Apr 25, 2013.

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  1. N_Cook

    N_Cook Guest

    2007 made Marshall 2266. Someone had been in there before and changed ECC83
    V3 and V4
    which function and tested fine. Impossible valve crackle
    V1 and V2 are probably originals , at least 07 dates agree
    V2 had a tested CH/R of 700K
    marked VLVE 0066 and grey shields dated 02/07
    V1 marginally acceptable (part of the valve sound) noise intrusion
    VLVE 0067 and shiney shields, dated 04/07
    with a tested CHR of 15M.
    Now both measure 25M or better, driving heaters to 13V for a couple of
    seconds and placed in my emergency- use pile of similar questionables
    Is this just random failures or are there know bad batches listed

    From an amp retailer insider source BlackStar amps have been hit by complete
    batches of amps with bad valves, did they take the same valve supplier they
    were used to at Marshall?
    In valve production is a routine final stage , over-driving the heaters to
    push back the oxide coatings of the heaters , if they happen to be marginal
    I know this fudge , like for the 700K one above is only temporary in that it
    will return after a few hundred hours of normal use, without vibration/abuse
  2. Phil Allison

    Phil Allison Guest

    "Nutcase Kook"

    ** LOL.

    Would that be the ECC81s they use for OUTPUT valves in their mini amps ?

    No kidding, the two halves operate in class A push-pull ( 300VDC supply) and
    deliver about 0.5 W into an 8 ohm speaker.

    But not for long ................

    ** The "supplier " is not too relevant.

    AFAIK China only has one factory making audio valves.

    .... Phil
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