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HELP hifi am audio in a cybernet pll02a clone like ge 3-5819a or rca 14t305

Discussion in 'CB Radio Modifications' started by kc2koj, Aug 29, 2013.

  1. kc2koj

    kc2koj
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    can someone help me out and take a look at this schematic and tell what to change out or to bypass to get fuller hifi tx am audio... looking for loud natural with good range for bass and treble ....what caps should I change or would I be better off trying to inject mic input at a different point ....Thanks ^^ ab v c^^


     

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    #1 kc2koj, Aug 29, 2013
    Last edited: Aug 29, 2013

  2. JoeDirt

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    C94 is what you want to bypass the audio amplifier, your only limiting factor will be the audio transformer.
     
  3. kc2koj

    kc2koj
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    can you please explain .....what should i do ?????? should i pull c94 and just bridge soder points... or inject mic input there... or would i be better off changing value of c94 thanks
     
    #3 kc2koj, Sep 5, 2013
    Last edited: Sep 5, 2013
  4. kc2koj

    kc2koj
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    after looking things over a little more i think you ment inject mic input on + side of c94 if i were to pull i would have no rx sound out speaker right .....anything eles i can change to give better tx audio ..........and on the rx side anything i could change there to make improvements .....anyone with any advice please chime in thanks
     
  5. JoeDirt

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    You want to inject to the negative side of the cap.

    Yes it looks like you lose RX, might need a relay.

    Improving RX would be a chore, you also still limited on TX and RX by the audio transformer.
     
  6. JoeDirt

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    You're almost better off getting a Cobra 148 or Grant XL, You can make improvements on this radio but not much.
     
  7. loosecannon

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    so, just a disclaimer, ive never done this to this chassis before, but it looks to me like these changes would help:

    C80- .001uF (TX)
    C81- 1uF (TX)
    C83- 1uF (RX and TX)
    C82- 100pF (RX and TX)
    C75- .47uF (RX)
    C94- 470uF (RX and TX)

    joedirt is right about the audio transformer choking the bandwidth, but you should still notice some improvement.

    the parts values i chose for the changes are just guesses.
    the changes should be done one at a time, and the effects noted.

    the general rule is to increase the series capacitance and decrease the parallel capacitance, which is what ive done in the changes i suggested.

    for example, i chose 1uF for C83. you may find that this is way too bassy, and you might want to try a .47uF, or maybe even a .22uF capacitor.

    one thing to note here is that electrolytics should not be your first choice.
    ceramic and mylar caps are better for audio tailoring.

    good luck, and please do post your results for the benefit of others who my run across this thread in the future.
    LC
     
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  8. kc2koj

    kc2koj
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