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Uniden Tempo 2020

Discussion in 'Amateur Radio Modifications' started by kopcicle, Sep 18, 2017.

  1. kopcicle

    kopcicle Well-Known Member

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    It's parentage sometimes confused with Yaesu (the Tempo One was Yaesu) and the Uniden applied to other than the US radio which was Henry, The 2020 is an interesting Hybrid in two ways. First it uses the 12BY7A driver and the 6146 pair as do many other Hybrids. Second is the curious Hybrid synthesizer that not only uses a dial for the last digits but spans 100KHz in 5 steps. The Yahoo group dedicated to Tempo 2020 is a great resource.

    Now onto the "fun"

    My 2020 came to me with a broken sprocket set. This makes the radio useless. With many thanks to Wald, N4PL and Gregory, NR6C I proceeded to restore this radio.

    [​IMG]

    [​IMG]

    This is typical of ALL of these 30 plus year old radios . There have been adaptations of other sprockets and temporary fixes that used small clamps, tie wraps, tie wraps and glue or circlips. Forget about it , all of it . f you are going to get into the radio at all, do it right.

    [​IMG]

    A thing of beauty. These are 3D printed and machined centers. They are made from a much more stable plastic and should outlast the radio or operator. My only suggestion to to Greg was to include a couple extra setscrews as they are easily lost. It is so very rare these days that you can close your eyes, sign the check. and be happy. That is exactly what happened here. The ID of the sprockets was so close that minor stoning of the shafts was in order to remove burrs from the original set screws.

    [​IMG]



    As you can see if just one of these sprockets is off the radio is essentially junk. I'll admit to having to do the install no less than three times as I was "one off" the first two times. I got pretty good at getting into the front of the radio which I'll share next .

    Many thanks to W7CPA, N4PL and NR6C for the images and text
    W7CPA here
    http://www.arizona-am.net/PHOENIX/W7CPA/Tempo 2020 Restoration Notes.pdf
    NR6C here
    http://nr6c.com/TEMPO SPROCKETS.htm
    N4PL here
    https://groups.yahoo.com/neo/groups/TEMPO_2020/info
     
    #1 kopcicle, Sep 18, 2017
    Last edited: Sep 18, 2017
    LeapFrog and Robb like this.

  2. kopcicle

    kopcicle Well-Known Member

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    Front panel removal
    is required to change lamp inside drum, replace toggle switches and fix/replace
    sprockets.
    1.
    Remove top and bottom covers.
    2.
    Remove front bezel by unscrewing all stainless counter sunk Phillips screws top, sides and bottom. Carefully pull forward. This was a very tight fit on my 2020.
    3.
    Remove the following knobs:
    PRESELECT, PLATE, LOAD and BAND MHz.
    4.
    Remove the top Phillips to the right of center that secures the front to the chassis
    5.
    Remove the bottom Phillips to the left of center that secures the front to the chassis.
    6.
    Carefully rotate the front panel forward to clear the PRESELECT, PLATE, LOAD and BAND
    MHz shafts. It has hinges on the bottom that allow a 90 degree tilt forward over the edge of a
    desk – a very nice design.
    7.
    Be careful rotating the front panel down since the mode switch has exposed diodes on the back.
    I had one break off the lug.
    http://www.arizona-am.net/PHOENIX/W7CPA/Tempo 2020 Restoration Notes.pdf

    Above from W7CPA

    I recommend that the radio with out its covers be placed on the bench with the front 2" hanging off the bench to make the "side and tilt easier. Also these are old radios and the wiring on the bottom of the chassis needs to be protected. Just a inch or so of some support under the outside chassis rails will elevate the wire looms.

    While you are inside the front panel replace the bulbs and service anything else you may need to as it really isn't that difficult but it does take time.

    Next , audio...
     
  3. kopcicle

    kopcicle Well-Known Member

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    Using a crystal element (as delivered in a Turner 254 desk mic) the hum disappeared . The audio was a bit low so I dug into the TA7063p data sheet and found the spec was a 22k ohm feedback resistor . The bit in the radio was a 6.8K ohm . I installed a 15k ohm at R551 and replaced the 4.7uf output cap at C532 with a 10uf . There is a capacitive resistance network on the input to the TA7063p but didn't play with it . ( C529 , R547 a 10k through followed by a 100pf to ground and the 100p at C527 . Q506 then has its part to play . )

    I finally settled on an old Shure Brothers 520B controlled reluctance cartridge that just likes my voice.
    Do be aware that Ground is Ground but Shield is Shield . Confuse the two connections to the mic input and curious things happen.
     
  4. kopcicle

    kopcicle Well-Known Member

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    I had a conversation with Nomad Radio today and other than the usual BS I got talked into writing this up . It's a great radio that deserves a better fate than the junk heap just for the lack of sprockets.

    It's all Nomad's fault , that's my story and I'm sticking to it !

    NOTE:
    If you have a Kenwood Hybrid with the same issues , NR6C also produces those parts as well .
     

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