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Cobra 29 meter stopped working.

Discussion in 'CB Radio Forum' started by Sasquatch308, Jun 15, 2019.

  1. Jun 15, 2019 #1
    Sasquatch308

    Sasquatch308 Bobtail Member

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    Jun 15, 2019
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    The meter quit working on my Cobra WX NW ST radio. The needle bounces when you shake the radio so the needle isn’t stuck. When you key the mic the needle just flinches. Is there a way to check the meter to see if it’s the meter or something else wrong with the radio? I pulled the cover and the solder joints look good, and I put a dmm on the back of the meter and measures 80mV with the mic keyed.
     
    Sasquatch308, Jun 15, 2019
    Sasquatch308, Jun 15, 2019
    #1
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  3. Jun 16, 2019 #2
    Night Stalker10

    Night Stalker10 Road Train Member

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    Is the swr/cal/rf switch in rf mode?
    The easiest way to check a meter, is if you have an old working meter, is to clip the wires to the original meter, and see if it works. Of course not everyone has a spare meter.
     
    Night Stalker10, Jun 16, 2019
    Night Stalker10, Jun 16, 2019
    #2
  4. Jun 16, 2019 #3
    Sasquatch308

    Sasquatch308 Bobtail Member

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    Jun 15, 2019
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    Yes it’s in RF mode. No I don’t have a spare meter. Have a couple old radios at home, but won’t be back till next week.
     
    Sasquatch308, Jun 16, 2019
    Sasquatch308, Jun 16, 2019
    #3
  5. Jun 19, 2019 #4
    Night Stalker10

    Night Stalker10 Road Train Member

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    There are a couple of things it could be. D12 is the rectifier diode for the meter. With the positive probe of your DMM on the cathode side of diode 12, it should read around 1.1 volts DC with the mic keyed. Capacitor C81 is a 4.7 microfarad filter capacitor, if it’s bad or has a bad solder joint, it could keep the meter from working. Also the VR pot that adjust the 4 watt power out on the meter is VR5. If this is an older radio, sometimes these pots need to be cleaned. You can use a pencil and gently push on the board to see if the meter starts to work, while the mic is keyed. Just an easy way to check for cold solder joints.
     
    Night Stalker10, Jun 19, 2019
    Night Stalker10, Jun 19, 2019
    #4
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