Tuner repair question

Discussion in 'Radio Circuits, Repair & Performance' started by N4NOO, Dec 22, 2019.

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  1. N4NOO

    N4NOO Ham Member QRZ Page

    I have a Palstar AT4K tuner that has a broken "connector". The inductor shaft has a "plastic" piece between the inductor and the shaft that comes thru the face of the case. This little part has broken. Anyone ever encountered this and if so, how did you repair it?
    Thank you,
    Rick - N4NOO 3.jpg 2.jpg 1.jpg
     
  2. W5RKL

    W5RKL Ham Member QRZ Page

    What is the control shaft's "O.D"?

    There are plenty of "flexible" couplers available on eBay, you just need to know the O.D. dimension
    the coupler will accept. Most, not all, shaft's are 1/4" O.D. shafts.

    73
    Mike W5RKL
    https://www.w5rkl.com
     
  3. G0GSR

    G0GSR Ham Member QRZ Page

    Email Palstar, they are very helpful with spares.
    Its an insulated, flexible coupler.

    Frank
     
  4. K9YLI

    K9YLI Ham Member QRZ Page

    Marlin P Jones. mpja.com.. all kinds and sizes of insulated couplers..
    and lots of other neat stuff...
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    As posted above, Palstar can probably sell you an exact replacement part but if that doesn't work out there are many insulated couplers available from other sources like here:
    https://www.rfparts.com/capacitors/capacitors-shaftcoupler.html

    or here:
    http://www.surplussales.com/shafthardware/ShaftH-10.html

    or here if your shafts aren't standard 1/4" size:
    https://www.mcmaster.com/flexible-shaft-couplings

    In addition to replacing the broken coupler you should check for excessive friction or binding of the roller inductor as something caused that flexible coupler to break. It could just be a poorly mounted roller inductor that results in excessive eccentricity of the two shafts and forced the coupler to flex more than necessary every time it was turned which looks like it might be the case from your first photo. Ideally the shafts would line up very close to a common axis so the shaft coupler doesn't have to flex too much as it rotates.
     

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