Bad Audio Transmit on Icom 2720

Discussion in 'Radio Circuits, Repair & Performance' started by KE5IRN, Jan 24, 2008.

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  1. KE5IRN

    KE5IRN Ham Member QRZ Page

    I just purchased a used Icom 2720 from one of those ham trade equipment boards.  This is my second 2720.  My first 2720 is first rate!  No problems!  This second 2720 exhibits the following:

    -it has good RF power output at antenna (as judged by other hams on the local repeater)
    -it is full quieting into the repeater

    -the audio volume is exceptionally low.  this is a problem.  bad audio amp in the radio?
    -this audio problem exists even when I trade out microphones from my good Icom unit

    -I am using an Astron VS-35 power supply
    -When attempting to transmit full power (35 W) on 70cm, the system instantly trips the household circuit breaker

    What is the problem?  How do I fix it?
  2. K9YLI

    K9YLI Ham Member QRZ Page

    How does your tone signal gget to the repeater.
    If tone level is ok and not distorted, then likely the first audio amp
    as I think the tone is inserted after the first amp.
    I didnt look at my schematic recently.
  3. KI6NNO

    KI6NNO Ham Member QRZ Page

    Do you have a 0.3A circuit breaker in your house??? [​IMG]

    I can't think of anything that would cause the breaker-tripping problem other than 70cm RF getting into your house wiring (there's no 35W option on 2M). That's definitely something I'd fix before worrying about the audio, if the audio problem isn't just a matter of setting a menu option.

    The 2720H has both Wide (5KHz) and Narrow (2.8KHz) deviation capabilities. Go into the SET menu and check that Wide FM ("OF") is selected (left band only).

    The mic gain is set during power up. Hold SET and push POWER for 1 sec. Go to the mic gain menu and make sure the mic gain is set to high "H".

    Also, the 2720 has had issues with RF getting into the mic. Take a look at to address this and other 2720 issues.

    Hope this is helpful.
    73, Dave
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