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Repairing the R-4B Calibrator

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  • querencias
    Any advice on how to trouble shoot the calibrator/ Get a fuzzykind of buzzing noise when it s turned on? Suspect the crystal or the flip-flops? Grant
    Message 1 of 3 , Dec 1, 2010
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      Any advice on how to trouble shoot the calibrator/ Get a fuzzykind of buzzing noise when it's turned on? Suspect the crystal or the flip-flops?

      Grant
    • Garey Barrell
      Grant - Your problem is almost certainly C192 and/or possibly C190. You can verify by just bridging a good cap across one of those with clip leads as the
      Message 2 of 3 , Dec 1, 2010
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        Grant -

        Your problem is almost certainly C192 and/or possibly C190. You can
        verify by just bridging a good cap across one of those with clip leads
        as the problem is high ESR, not leakage.

        If they are gone, the can cap C90 and tubular cap C91 are probably not
        long. A good fix is the re-cap kit from 'hayseedhamfest.com'. Tom has
        a complete set of all electrolytics for a very reasonable price. All
        electrolytics in that receiver are way past their life expectancy, and a
        'shorting' failure can take out a power transformer. Be sure you have
        the correct size fuse in place!

        73, Garey - K4OAH
        Glen Allen, VA

        Drake 2-B, 2-C/2-NT, 4-B, C-Line&
        TR-4/C Service Supplement CDs
        <www.k4oah.com>


        querencias wrote:
        > Any advice on how to trouble shoot the calibrator/ Get a fuzzykind of buzzing noise when it's turned on? Suspect the crystal or the flip-flops?
        >
        > Grant
        >
        >
      • Larry Taft
        New filter cap in the DC supply feeding the calibrator. Larry K2LT drakerepair.com
        Message 3 of 3 , Dec 1, 2010
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          New filter cap in the DC supply feeding the calibrator.

          Larry K2LT
          drakerepair.com

          On 12/1/2010 11:07 AM, querencias wrote:
          > Any advice on how to trouble shoot the calibrator/ Get a fuzzykind of buzzing noise when it's turned on? Suspect the crystal or the flip-flops?
          >
          > Grant
          >
          >
          >
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