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Uniden 66XL help and tune tips

Discussion in 'General CB Services Discussion' started by CB590, Dec 31, 2019.

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  1. CB590

    CB590 W9WDX Member

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    8AA9365E-382E-46D9-91D6-4027C9FC444D.jpeg

    Got this coming in. Was cheap enough and appears minty and supposedly only has talkback and tune. Does 4w and swings to 20w on guys Dosey.

    Would turning L10 down lower my dk?? Or is there something else I should look to adjust?? I may decide to run an amp with it hence the questions.

    What other things should I look for when I pop the top as far as cut things??



    Happy New Years and thanks folks.
     
    Shadetree Mechanic likes this.

  2. CB590

    CB590 W9WDX Member

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    How do I disable or remove the talkback someone installed.

    Here's the pics. L13 slug missing. Mic jack has resistor going to top of L7 can on right.

    200AC24A-30DB-4FBD-81F8-186C2EEAF734.jpeg

    And corner where speaker plugs in

    2C8975AF-1724-42DC-BA0F-1C7814E8FA46.jpeg
     
  3. Robb

    Robb Yup

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    The talkback resistor is on the underside of the board between the PA jack and the speaker jack . . .
     
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  4. CB590

    CB590 W9WDX Member

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    Not seeing anything

    57FEE14D-CF4A-42EE-B0A3-0A1A6AFD751B.jpeg

    4422225B-0496-43AC-952D-D61BF2494173.jpeg
     
  5. hotrod

    hotrod Well-Known Member

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    those are great lil am radios. i dont remember the tune up process but i was thinking theres 3 cans total ...but i cant remeber
     
  6. Low_Boy

    Low_Boy Well-Known Member

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    Possibly the metal ring in the jack is touching the shassis. That will give you talk back.
     
  7. CB590

    CB590 W9WDX Member

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    Could this be it here?? I magnified the pic from earlier.

    looks like something to ground going on, or is that normal??

    7AF9ADB0-2044-4C17-A65C-F675265A2026.png
     
  8. NZ8N

    NZ8N Active Member

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    PC66 Talkback.jpg

    75 Ohm resistor, here is your talkback, in kind of a hokey place to put it, most people put it across the PA and speaker jack terminals on the foil side of the board.
     
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  9. CB590

    CB590 W9WDX Member

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    I took this as well from the bottom. Wonder that that little capacitor is for on that side??

    CFE1B3DA-47A3-4B64-B052-58040C873D9B.jpeg
     
    #9 CB590, Jan 3, 2020
    Last edited: Jan 3, 2020
  10. CB590

    CB590 W9WDX Member

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    So the resistor from the Mic jack to the top of L7 "can" is the culprit??

    I had remembered reading like 3-4 years ago about people doing it that way.
     
  11. NZ8N

    NZ8N Active Member

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    PC66 Talkback usually here instead.jpg

    Yes, it is usually between these 2 terminals.
     
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  12. NZ8N

    NZ8N Active Member

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    PC66 Overmod mod.jpg

    PC66 Jumper JP6.jpg

    Now, back to the original post about dead key adjustment, with this installed, it has a "swing kit" or "supermod kit", which lowers the dead key and the capacitor causes it to swing high on positive peaks of the audio. This replaces JP6. Depending on the resistor value under the capacitor, will determine the dead key. They usually cut off the negative peaks, having Zero carrier between spoken cyllables. Very hard to adjust correct modulation without an oscilloscope to watch the pattern.
    If you put a jumper wire on the back side of the board, shorting across this resistor/cap mod temporarily, repeak the radio, then take the jumper off, thereby re-enabling the mod, the carrier should lower with the mod. Could also make it switchable.
     
    #12 NZ8N, Jan 3, 2020
    Last edited: Jan 3, 2020
    Shadetree Mechanic and CB590 like this.
  13. loosecannon

    loosecannon Sr. Member

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    the other guys have you handled on the talkback thing.

    on that little cap on the bottom of the board, can you tell us which two components are being connected by it?

    the solder to the case of the radio is just for the bypass caps that connect PC board ground to chassis ground.
    CB radios used to all be made with what is called a floating ground, so that you could put them in positive ground vehicles.
    that's why the chassis ground is not just wired right to the PC board ground, but is done through capacitors.


    EDIT: NZ8N's method will work also.

    as for lowering your deadkey, don't de-tune the can, as that just creates an impedance mismatch in the final section of your radio, and will lower swing as well as deadkey.

    the way to do it is to add diodes in series with D10, the anti spiking diode located near VR3. i believe it's a 1N4003.
    each diode you add in series will drop the voltage going to the collector of the driver and final by .6 volts, and therefore, will lower the deadkey.
    keep adding them till you get to the deadkey you want.
    the great thing about doing it this way is that all the audio will still be passed 1:1 by the diode since it's already biased ON when you key up.
    try it, you'll like it.
    LC
     
  14. CB590

    CB590 W9WDX Member

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    Could they have just cut JP6 all together and attached the cap legs to that?? It kinda looks like no resistor under it.

    I was planning on running with my Palomar Elite 400 which can handle the 20w or so swing. And at the moment with this 66xl my meter is showing a hair under 100w dk. When I talk the power actually goes downward towards 60w and SWR climbs.

    I did notice the L13 slug is missing also. Which is another tuning point for power. :/
     
  15. CB590

    CB590 W9WDX Member

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    Talkback is now undone. (y)

    The dropping of dk may have to just wait or be left alone. I'm not a tech at all. I always send things out, which you know is $20 each way to ship.

    I have a harbor freight 30w iron that needs a new tip and no tools for more than soldering a wire or clipping one off.

    Lowering the dk was just a thought. Just wish classic radios were left alone and not with torn out slugs and dodadds added.
     

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