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Thread: VX-8DR MIC/SP clicking sound from speaker problem

  1. #1

    Unhappy VX-8DR MIC/SP clicking sound from speaker problem

    Hi

    Recently I bought a CT-M11 cable for my Yaesu VX-8DR to attach a custom headset to it. But there is a problem: when radio speaker is idle (not emitting any sounds like from receiving something or after pressing buttons) the clicking sound appears from the speaker attached to the MIC/SP connector (the one on top with many pins).
    I've checked it with oscilloscope and it looks like a single spike exactly every 400mS.
    Changing volume setting does not affect clicking volume, also no clicking appear on built in speaker or on the earphones connected to with 3.5mm jack on the side of the radio.

    It's really strange and annoying and definitly not possible to use headset with those clicks.
    I was wondering if anyone had the same problem? Is it hardware related or can be solved by softwatre?

    I've already sent a letter to the official Yaesu support and if they answer something usefull - I will post here.

    Thanks.

  2. #2

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    Are you on a local repeater frequency ? High voltage power lines nearby ? A line transformer nearby ?

    Are there other hams in your area that you can contact to see if they have the same problem ?
    --
    73, Jim/N4AAB got my Extra class license on Aug 10, 2017. Vanity call in Oct, 2014.
    My Ham radio site has no popups, no music, no banners.
    'Through the thorns to the stars' from Ghost-in-the-Shell anime.

  3. #3

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    Hi, thanks for your answer

    The sound is definitely an internal problem of the radio: It does not depend on input frequency (basically I can replace antenna with dummy load and it will still be there)
    Also no sources of EMI nearby my workbench.

    Unfortunately I found no owners of this radio nearby. Official support is not answering (despite their webpage tells they will answer in 2 days, ha-ha)

    I found a repair manual for this radio: http://www.radioaficion.com/hamfiles...service-manual
    And on page 91 there is a circuit responcible for speaker and headphones an this 7 pin connector, which is built on NJM2151A chip
    Datasheet: https://www.mouser.com/ds/2/294/NJM2151A_E-59797.pdf
    So I think I will disassamble the radio and probe it.

    Also if anyone has schematics of external speaker/microphone MH-74A7A - I would be just hapy to see it, maybe they just have some additional speaker disabling circuit inside it to suppress clicks.

  4. #4

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    You say this is occurring with an external mic/speaker, correct? Does the same thing thing happen with the speaker built into the radio? If You disconnect the adapter cable and headset and the problem goes away, then it's not the radio. It's in the adapter and/or headset.

  5. #5
    Super Moderator 5B4AJB's Avatar
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    Its not a power-saving feature turned on? I noticed this on my Icom P2E when I first got it.
    Go through the menus & disable any power saving options, see if that helps...

  6. #6

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    Quote Originally Posted by 5B4AJB View Post
    Its not a power-saving feature turned on? I noticed this on my Icom P2E when I first got it.
    Go through the menus & disable any power saving options, see if that helps...
    Man! Unbelievable! You are right! It was "Save RX" function: It puts radio to sleep for some time and then wakes it to check for incoming signals. I changed those sleep intervals (menu item #79) and the period between clicks changed accordingly, I turned it off and clicks disappeared. THANKS! The bad news is: now the battery will draw faster.
    BTW, it means that speaker amplifier is not decoupled properly, which is disappointing, especially for that radio price...
    Last edited by dramin; Sun 26th May 2019 at 18:52.

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