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uniden washington no tx output

Discussion in 'CB and Export Equipment and Accessories' started by 479tx, Feb 10, 2013.

  1. 479tx

    479tx Member

    Oct 12, 2011
    Likes Received:
    Uniden Washington, no tx power. Looking at it for a friend. This thing is really nice inside and out except for the stupid channel mod/unlocked clarifier crap.

    Excellent RX, but no rf output.

    - mic changes transmit indicator to red, receive drops out like it should (mic is wired correctly)
    - PA works
    - in AM mode, if you switch the meter to %mod, I see the meter move with modulation (although no rf output)
    - LSB/USB no indication on %mod meter
    - LSB/USB no rf output

    Bad final? Is there an easy way to check with it inline?

  2. 479tx

    479tx Member

    Oct 12, 2011
    Likes Received:
    Well, before doing much troubleshooting I swapped the 1969 final with a known good one. Same thing, no visible RF output on a watt meter @ 20 watt scale in AM or SSB.

    I plugged a radio in right next to it and I can hear the TX audio on AM when the monitor radio is on the same channel.

    Went checking for voltages and realized the internal power supply has some kind of problem, only ~2.3v on the rail at idle. Plugged radio into an external power supply and checked voltages:

    13.8v on the AM regulator
    13.8v on the final & driver at ide
    6v on the final & driver on AM TX
    13.8v on the final & driver SSB TX

    the above seems good, I still have yet to replace the driver, if the driver was bad but final was good could this cause what I'm seeing? Maybe the driver and final were blown all along and I just need to replace the driver as well.
  3. Robb

    Robb Yup

    Dec 18, 2008
    Likes Received:
    The easiest and best way to check the driver or final is to unsolder their leads from the board and then test them.

    Look at changing out the regulator with the TO-220 case in the PS.
    But test the output voltage from the xformer to the rectifier first.

    If this radio has the 8719 PLL chip; then be sure to do the service bulletin #1226 procedure.
    A MUST for any Uniden chassis with the MB3756/8 volt regulator.
    #3 Robb, Feb 10, 2013
    Last edited: Feb 10, 2013

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