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    Jon Burgstrom
    Forum Participant

    Hello all,

    I am a new member interested in the Stark Tube Tester model series 9-66.

    I would really appreciate it if someone could inform me of what the differences are in the Stark Models 9-66, 9-66A and the 9-66AU? I believe they follow the Hickok 533, 533A but I am unsure, especially with concern to the 9-66AU. If you have any Internet resources on the 9-66AU model that may be helpful I would surely appreciate a link to that as well.



    Murray Dickerson
    CVRS Member

    Hello Jon:

    The original Stark 9-66 just had test sockets for all the older tubes including 4,5,6,7 pin tubes, up to Octals, Loctals, 7 and 9 pin miniature type tubes; in other words, tubes that had been produced up to the early 50’s.

    The 9-66A included an auxiliary panel (screwed into the test lead compartment) that had special purpose tube sockets for European and industrial tubes. These sockets were still limited to a maximum of 9 pins like the older set in the 9-66.

    The 9-66AU was a later version upgrade that included most of the former tube sockets in the 9-66A, but also added the later version compactron types up to 12 pins. These tubes started to appear in the late 50’s and were used extensively in TVs to reduce tube numbers and production costs.

    Note that all of the test settings were still the same as in the earlier models. Another way of saying that is that the 9-66AU was downward compatible. However, the 9-66 and 9-66A’s were not upward compatible with the 9-66AU since 12-14 position setting switches were needed to accommodate the newer compactron types that only the 9-66AU could handle.


    Jon Burgstrom
    Forum Participant

    Hi Murray,

    Thank you for your response. If you can, could you answer a couple of other questions? Did the 9-66AU also lower the grid signal from ~5.0 Volts AC to 2.5 Volts AC? I have only been able to find info on the 9-66 on the internet. Do you know of any links that discuss the differences between the models in any greater detail?

    Thank you in advance,


    Dale Dieterle
    Forum Participant

    I bought a Stark 9-66A back in the late 1960’s,or 1970’s. I bought a universal add-on adapter, that came with installation instructions from Stark. This adapter screwed into the top compartment of the tester.The 9-66 models are based on the Hickok 533 circuits.There is four models,
    the 9-66, 9-66U, 9-66A, 9-66AU. The only difference is the tube sockets that were added. The 9-66 has nine sockets, 9-66A has twelve sockets. The
    9-66U has sixteen sockets including the adapter, that was factory installed. The 9-66AU has nineteen sockets installed at the factory. The 9-66 uses a 18 point filament switch,and the 9-66A, and 9-66AU use a 20 point switch,it has a off setting as well as a .63 volt setting. The 9-66’s use a signal voltage of 5 vac., same as the Hickok 533.
    Hickok built tube testers for other company’s such as the Philco’s 9100
    tube tester witch is identical to the 533A circuits.

    Have a nice day,
    Dale Dieterle

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