ICOM A20 PLL unlocked ( "u" displayed - error) ?

Discussion in 'Mobile Radio Systems' started by QHPLT, Jul 24, 2018.

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  1. QHPLT

    QHPLT QRZ Member

    HI there !

    A small "u" is shown where the Memory number should be....
    Can it mean that the PLL is not working properly ?
    Cant recieve , cant Transmit (at least at the Freq. i set)

    Any ideas ? It needs only a re-tuning ? Or replacing some Caps ?
  2. QHPLT

    QHPLT QRZ Member

    I have a func. gen and a 200Mhz DSO so i can "maybe" find and fix the problem if it will be a know way to do it.
  3. W9GB

    W9GB Ham Member QRZ Page

    The iCOM A20 is an Aviation industry hand-held radio, over twenty years old, that was discontinued before 2010.

    This web site is devoted to Amateur Radio ... you would be best served posting go an Internet web site and Discussion forums dedicated to to Aviation/Navigation communications.

    Icom America only has two (2) Amateur / Marine and Avionics repair centers, outside of Icom America’s HQ in Pacific Northwest. Both of those Icom service centers are adjacent to Lake Michigan (Chicago and SW Michigan).

    The Icom IC-A2 and IC-A20 are not longer supported Avionics products.

    Icom IC-A20 Processor Reset Procedure
    Push [F] & [CLEAR] buttons and turn the radio on.

    Icom A2/A20 External Microphone Wiring

    Pacific Northwest Flying

    Service Manuals for your radio can be purchased from Icom, Manual houses,
    or scanned copies (Google search).

    iCOM IC-A20 Manual (Japanese web site)
    Last edited: Jul 25, 2018
  4. GJ6WRI

    GJ6WRI XML Subscriber QRZ Page

    I have messaged you my reply, and should solve your problem.
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    Is the fix top secret ?

    I hope it works.
  6. GJ6WRI

    GJ6WRI XML Subscriber QRZ Page

    No! Not secret, I had just replied to his question directly emailed to me via the qrz mail.
    The U does indeed mean Unlocked, and relates to the PLL not being "locked"
    Replacing the crystal is all that is normally needed to resolve the issue.
    The radio is only good as an emergency backup due to the fact it isn't 8.33 compliant/compatible.
    KA9JLM likes this.
  7. QHPLT

    QHPLT QRZ Member

    So far i was able to fix this issue by re-tuning the PLL by using the Service manual... only a Voltmeter is needed for that (for more tuning.. scope and other devices)

    Despite this.... the reference freq. is off by 850 - 900 Khz so.... crystal has an issue here most probably.
    KA9JLM likes this.
  8. W9GB

    W9GB Ham Member QRZ Page

    Since International Crystal Manufacturers (ICM) of Oklahoma City shutdown last year,
    problematic for good custom crystal source in North America.

    For Europe, contact QuartSLab with specifications for replacement.

    68 London Road
    Dunton Green
    Sevenoaks, Kent
    TN13 2UG
    United Kingdom

    Telephone from United Kingdom: 020 7100 6357
    Telephone International: +44 20 7100 6357
    E-mail: sales2@quartslab.com

    Last edited: Jul 29, 2018
  9. QHPLT

    QHPLT QRZ Member


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