How to increase Motorola HLN5459A Microphone Gain?

Discussion in 'Microphones, Speakers & Audio Processing' started by TA3N, Nov 21, 2020.

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  1. TA3N

    TA3N Ham Member QRZ Page

    Hello my friends,
    I have Motorola HLN5459A on my Motorola Astro but the microphone gain is very low. Modulation is very low. How can i increase microphone gain? I tried to increase it from the radio settings but it did not work. Can I modify the microphone to increase it? Or do you have any suggestion? Thank you. 73.

    You can find the Motorola HLN5459A photos in the attached files.

    TA3N
    Sezgin Kenar
     

    Attached Files:

  2. W9GB

    W9GB Ham Member QRZ Page

    Did you TEST the Elecret microphone element?
    They can FAIL, but are DIRT CHEAP (usually less than $3 USD ... anywhere)

    There is a Transistor on the PC board (Q1302, M8208) that serves as pre-amplifier.
    IF that failed ... it would cause your problem. TEST It !
    How to Test an NPN transistor? VOM/DVM : Internet has instructions & videos.

    ====
    Motorola HMN 1052A microphone
    PC Board, inside that microphone, is part number: HLN5459A
    Here is the Parts List, PC Board Layout, and Schematic Diagram (circa 1989)
    http://www.radiomanual.info/schemi/ACC_microphone/Motorola_HMN1052A_sch.pdf

    Possible M8208 substitutions (standard global electronics part distributors):
    2N4424
    https://my.centralsemi.com/datasheets/2N4424.pdf
    2N3904
    https://my.centralsemi.com/datasheets/2N3903.PDF
     
    Last edited: Nov 21, 2020
  3. TA3N

    TA3N Ham Member QRZ Page

    Thank you for the information, my m8208 and Electret microphone element are working pretty well but I want to increase microphone gain. My modulation recieved by the other stations is very low so I want to increase the modulation. If i change it to the parts you suggested, will it increase the microphone gain? Or do you have any other suggestions?
     
  4. WA0YDE

    WA0YDE Ham Member QRZ Page

    Replacing the microphone element is THE FIRST THING to try. They still work, but sensitivity falls off. I have replaced hundreds!
     
  5. WA0CBW

    WA0CBW Ham Member QRZ Page

    Does it have the correct input voltage?
    Bill
     
  6. COLLIN35

    COLLIN35 QRZ Member

    I'm also having the same issue, but if I got any solution I'll let you know GarageBand for PC
     

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