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  • March 7, 2015 at 10:48 am #6628
    Pentode
    Forum Participant

    I am fixing up a 1954 AM Marconi radio. I recap it and it runs good once tuned to an AM station however I get motorboating between the stations. Any ideas? I check the tubes and shields but all looks good.

    March 9, 2015 at 6:06 am #6649
    Peter Heembrock
    Forum Participant

    Sounds like it could be an AGC related issue…have you checked all resistor values as well?
    Has the set been re-aligned?

    March 9, 2015 at 8:28 am #6653
    Dan Walker
    CVRS Member

    Google ”Motorboating” What it is, and why.. The article might give you some helpful information.

    March 9, 2015 at 10:18 am #6654
    Peter Heembrock
    Forum Participant

    See attached pdf article from may back…

    Attachments:
    1. How-To-Fix-a-Receiver-That-Squeals-and-Motorboats.pdf
    March 9, 2015 at 8:43 pm #6665
    Rob Uthe
    Forum Participant

    Also make sure that your coupling cap replacements aren’t too high (eg 0.1 uF instead of 0.01 uF).

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