300 Ohm headset question

Discussion in 'Avionics and Upgrades' started by Scott Johnston, Nov 17, 2020.

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  1. Scott Johnston

    Scott Johnston Filing Flight Plan

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    Good afternoon,

    I did a search for "headet" and "potentiometer" and came up with nothing in this forum so here goes the question. Can any of you tell me the standard value for headset potentiometers? I'm dealing with a David Clark "clone" that has a faulty pot. The headphones Ohm out to 150 Ohms. The pot I pulled out of the unit was stamped 81K but I highly doubt that's the range. I would expect to need a 150 Ohm potentiometer in series to manage volume on the headset. Any experts out there? I was a Avionics Tech on the EA-6B Prowler in the Navy but I never had a headset go bad in the field.

    Many thanks,
    Scott
     
    Scott Johnston, Nov 17, 2020
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  2. GeorgeC

    GeorgeC Administrator Management Council Member

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    GeorgeC, Nov 17, 2020
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  3. Dana

    Dana En-Route

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    You can't check headset impedance with an ohmmeter, AC impedance is different from DC resistance.
     
    Dana, Nov 17, 2020
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  4. Scott Johnston

    Scott Johnston Filing Flight Plan

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    The pot doesn't say 81K it says B1K! Makes total sense after looking at GeorgeC's PDF file that he linked. At this point I've ordered what I need. Thanks all.
     
    Scott Johnston, Nov 17, 2020
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  5. flyingron

    flyingron Administrator Management Council Member PoA Supporter

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    You can not reliably measure impedance with a DC ohmmeter.
     
    flyingron, Nov 17, 2020
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  6. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    But you can measure the pot - which is what the OP asked about.
     
    Capt. Geoffrey Thorpe, Nov 17, 2020
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  7. flyingron

    flyingron Administrator Management Council Member PoA Supporter

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    He didn't measure the pot, he said he "ohmed out the headphones" at 150.

    His idea of how the pot works is defective either. It's not expected that the pot be equal to the overall impedance.
     
    flyingron, Nov 17, 2020
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  8. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    I stand corrected.
     
    Capt. Geoffrey Thorpe, Nov 17, 2020
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