Yaesu VX1R - Audio has become unintelligable

Discussion in 'Radio Circuits, Repair & Performance' started by G0LQU, Jul 16, 2012.

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  1. G0LQU

    G0LQU Ham Member QRZ Page

    My VX1R has gone from working perfectly for several years to suddenly developing this audio fault. It TX's OK with carrier (e.g.for repeater access with CTCSS) but my son reported that the audio from the built-in microphone has become unintelligable. If I whistle into the mike, this is transmitted, but not speech. My son also said it sounds like a transistor in the audio amplifier circuit has become "unbiased" as the sound is similar to a problem he had on an audio amp.

    2 simple questions:
    1. Does anyone know what the problem may be?
    2. Is it realistically possible to dismantle the rig and check anything!

    Mush obliged in advance for any thoughts.

    Peter G0LQU
     
  2. KE3WD

    KE3WD Ham Member QRZ Page

    The first thing I would do is substitute another electret condenser mic capsule.

    Have repaired quite a few rigs and HTs where the mic capsule died or got some moisture intrusion, with the full gamut of symptoms, from totally dead to things such as you report here.

    A quick check for that would be to plug in one of those handheld mics or headsets that has the appropriate connector and connections and see if proper operation happens when using that. If so, it si a safe bet that the built in condenser element is history and in need of replacement.


    73
     
  3. G0LQU

    G0LQU Ham Member QRZ Page

    Thanks for the advice. All is not lost then! I had thought of trying a speaker/mike but its about £20 here and would be wasted if that was not the problem. I'll try to loan one. I assume that if the electret mike was the problem it is possible to replace it?

    Peter G0LQU
     
  4. KE3WD

    KE3WD Ham Member QRZ Page

    Yes, it is certainly possible to replace the built in condenser capsule, I do it quite a bit.



    73
     
  5. G0LQU

    G0LQU Ham Member QRZ Page

    OK Many thanks for that. I'll have a go (but may need to keep you for further advice if I get stuck - QRX!)

    Most grateful

    Peter G0 LQU
     
  6. G0LQU

    G0LQU Ham Member QRZ Page

    Problem solved! I managed to dismantle the radio and noticed that one of the SM chips had a peculiar brown deposit covering three pins. It could have been an electrolytic cap. leak but I didn't see anything that looked like an electrolytic cap. (although I am not familiar with SM components). Anyway, I cleaned the deposit off with a toothbrush and some IPA. (the chip was an audio amp so I thought it was highly suspicious!). on re-assembly - the audio was fine!

    Thanks for the help and encouragement to do this job!

    Peter G0LQU
     
  7. KE3WD

    KE3WD Ham Member QRZ Page

    Hi Peter,

    What you found is called, "Sonybond" adhesive. That formula is no longer used, but the stuff is out there in many consumer electronic devices. Brown in color, when it deteriorates, it is known to crystallize and also become ... conductive.

    You did the right thing by simply physically removing the bad stuff using small pointed or edged tools.

    And now you know where it came from and that it is not anything leaking in there.


    73
     
  8. G0LQU

    G0LQU Ham Member QRZ Page

    Thank you so much for that. I know its daft but I had become quite attached to that little rig and to get it going again with my limited technical knowledge was a great feeling for me. This forum gave me the confidence to "take it apart" and I'll always be grateful!

    best '73
    Peter G0LQU
     
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