Drake R-4A Slipping Preselector

Discussion in '"Boat Anchor" & Classic Equipment' started by WA4NJY, Nov 15, 2017.

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  1. WA4NJY

    WA4NJY Ham Member QRZ Page

    My R-4A preselector control has a slip at times. There is a "disc" looking device on the shaft directly behind front panel. Is this some kind of clutch to limit the force that can be exerted on the slug gang? If so, maybe someone has oiled it when it should be dry. A slight assist with my finger allows the slug gang and knob to move properly. Any input will be appreciated.

    Thanks,
    Ed WA4NJY
     
  2. WA4NJY

    WA4NJY Ham Member QRZ Page

    Have found some good info. Seems the problem may be wear in the vernier. May look for a good replacement. Doubt the eyes are up to a repair.

    Ed
     
  3. N8AFT

    N8AFT Subscriber QRZ Page

    Likely just a drop of light oil on the vari-cap shaft bearing surfaces will suffice, and make sure the knob is tight.
     
  4. KL7AJ

    KL7AJ Premium Subscriber QRZ Page

    Yep....I had the same issue.
    Oil is your friend.
     
  5. W5RKL

    W5RKL Ham Member QRZ Page

    The problem is caused by wear on the vernier shaft assembly, not the slug assembly.

    I copied the picture below from the link above the picture.

    Note the smaller shaft has a cut out or valley area on the right end. Also note there are
    4 ball bearings. Those ball bearings ride on the "cut out" area of the smaller shaft. The
    smaller shaft and ball bearings is inserted into the larger shaft shown on the upper left.
    The ball bearings provide friction between the smaller shaft and the larger shaft, hence
    a vernier drive assembly.

    Over time the ball bearings and cut out area wear resulting in reduced friction between
    the 2 shafts, hence slippage occurs.

    I had the same slippage on m R4B receiver. The fix was to replace the dual shaft vernier
    system with one that doesn't slip. The slug assembly is not replaced, only the dual shaft
    bearing assembly.

    http://history.k4lrg.org/Projects/Magic_of_Boatanchors/index.html


    [​IMG]

    Here's a link to a possible fix. I couldn't get this fix to work with my R4B
    vernier assembly so I replace the entire dual shaft vernier assembly with one
    from a Drake parts radio (Drake R4<any> or T4<any> receiver or transmitter) that didn't slip.
    I found a T4X parts chassis on eBay that had a complete vernier assembly that didn't slip.
    Now the R4B Preselector works just fine.

    https://www.google.com/url?sa=t&rct...oXP9KfNcytqE9w&bvm=bv.103073922,d.dmo&cad=rja

    73
    Mike W5RKL
    www.w5rkl.com
     
  6. WA4NJY

    WA4NJY Ham Member QRZ Page

    Thanks for the info gents. Mike is on the right track. I found some info from Gary, K4OAH that may be a way to save the vernier in my R-4A if a known good one is not found.

    73, Ed
     
  7. KE4OH

    KE4OH Ham Member QRZ Page

    Ed, please share that info if you can. I have the same issue with my Drake 2-C preselector. Oil did not work. I imagine it is the same part as installed in the R-4A.

    73,
    Steve KE4OH
     
  8. WA4NJY

    WA4NJY Ham Member QRZ Page

  9. W5RKL

    W5RKL Ham Member QRZ Page

    Ed,

    That link is the same as the link I included in my response.

    I could never get that fix to work which is why I went the parts chassis route.

    73
    Mike W5RKL
    www.w5rkl.com
     

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