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Help Uniden Grant XL

Discussion in 'General CB Services Discussion' started by paulsbox, Feb 14, 2018.

  1. paulsbox

    paulsbox
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    Uniden Grant XL PB-208 board. Can't get VCO frequencies to set. Alignment calls for AM L23 34.985 LSB L22 34.9835 USB L59 34.9865. I can not adjust it down any lower than 35.167 mhz. Changed the 11.325 crystal, changed L23 and check some diodes nothing made any difference.


     

  2. 357

    357
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    Walkin' the dog

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    possible conductive glue?
    are you on the correct channel to align it?
     
  3. paulsbox

    paulsbox
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    Yes, shows channel 19..
     
  4. nomadradio

    nomadradio
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    Analog Retentive

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    This makes it sound as if the PLL is out of lock.

    An unlocked PLL should not permit the radio to transmit, at all. FCC rules require a circuit that detects this "unlocked" condition and disables the transmitter when this happens.

    Do you have a 'scope or a way to borrow one?

    Never have learned how to troubleshoot a PLL circuit without a 'scope.

    73
     
  5. Robb

    Robb
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    Yup

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    There is yet another possibility here. If the clarifier has been unlocked WITH extending the range of the slide ('jumping the resistors'); then the center freq of the clarifier will be more like at the 2 o'clock position - rather than at the 12 o'clock position. Try that next.

    That is the reason I don't bypass those resistors as most clarifier mods ask to do. Sure it extends the clarifier slide; but it also makes it susceptible to drift, too much slide to dial someone in (IOW - too sensitive), and leaves the clarifier in a skewed position for its center slot. See this a few times. Just saying . . .
     
  6. paulsbox

    paulsbox
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    The radio will rx and tx, its just off frequency you can really tell on ssb. I tried turning the clarifier, but it still doesnt allow me to get below 35.167. yes i have a frequency counter, scope, vom, & signal generator.
     
  7. kaos513

    kaos513
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    crystal might be bad
     
  8. paulsbox

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    which one, i replaced the 11.325 and the 10.240 checked ok on counter.
     
  9. sonoma

    sonoma
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    did this radio have extra channels on it at one time?
    check pin 10 of the PLL and see if it is soldered to ground or not.
     
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  10. paulsbox

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    Update found problem, had the wrong ceramic capacitor in circuit. Had a 220pf a was suppose to be a 470pf. Thanks
     
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  11. sonoma

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    good find. it is very hard to try to help some one when a person has put a wrong part in line.
    good find.
     
  12. kaos513

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    great find !
     
  13. loosecannon

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    i noticed you posted that the alignment instructions stated L59 for the USB adjustment, and the Grant XL does not have an L59.

    which alignment procedure were you using?

    also, there are only two 470pF caps in the loop oscillator circuit, C117 and C212.

    which one of these caps was it?
    the reason i ask is i'm having trouble seeing how such a minor change in part value made such a big difference in the frequency?

    was the 220pf cap there from the factory?
    LC
     
  14. paulsbox

    paulsbox
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    It was c117, it had a 220pf don’t know if someone changed or not. It did have a expo kit in it. There is a L59, there was 2 different board on the grant xl, mine has the pb-208 board the other bleary that was used was the same as the older 148’s
     
  15. loosecannon

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    gotcha.

    thanks for the info on the PB-208 version. I've either never seen that version or have forgotten that i've seen one. LOL
    LC
     

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