The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all products and all products

    Tube tester



    Posts : 12
    Join date : 2011-01-22
    Location : Pittsburgh

    Tube tester

    Post by davek65 on Sat Jun 04, 2011 1:52 pm

    Hi all,

    I just bought a Accurate Instrument Co. Tube tester Mod 257 at a flea market for $30 .
    the case is in fairly good condition and the tester works . I tried testing one of the KT 88 tubes
    on it and shows good . What i wanted to know is anyone familiar with this one and is it any good.
    from schematics on line a test voltage of 25v is applied .I would like some input on this tester .

    I've been a member of this forum for a while i guess since i bought one of Bobs ST-120 kits . I love
    it . I think its the best out there and got lots of balls of output . I bought the ST 120 kit the
    first of the year .This is my first post.



    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey

    Re: Tube tester

    Post by Sal on Sat Jun 04, 2011 10:09 pm

    Hi Dave,
    For $30 you done good but be aware, it is a simple emission tube tester that will most part weed out the bad tubes but you cannot match tubes with it.

    Now I own over 20 tube testers and use my emission tube testers for quick tests, more so on antique radios but when I test audio tubes, I use a mutual conductance tube tester.



    Posts : 12
    Join date : 2011-01-22
    Location : Pittsburgh

    Re: Tube tester

    Post by davek65 on Sun Jun 05, 2011 8:55 am

    Thanks Sal,

    I should have known but didn't give it a thought . But since the ST-120 has separate bias adjustments
    for the output tubes i wasn't too picky on the tube matching . The mutual conductance TT's are
    a little pricey for me to buy just to have for only the ST-120 tube type audio component i have
    in my music system .In my younger years i probably would notice the difference but at 65 my
    ears aren't as good.I'm using a Carver SS tuner/preamp to feed the ST-120 so i don't do
    too much tube rolling .If the Carver breaks then I'll buy a tube preamp kit then probably a
    mutual conductance would be good.~Dave


    Posts : 58
    Join date : 2011-05-09
    Location : Albuquerque

    Re: Tube tester

    Post by Westy56 on Sun Jun 05, 2011 9:34 am

    Mu matching in an phase splitter is very important.


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