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  • March 24, 2016 at 4:23 pm #7622
    Les Dickson
    CVRS Member

    I’m working on an Emerson BM215. (I’m fairly new to playing with old radios and my electronics knowledge is limited.)

    When I check the resistance on the volume control – with no wires connected – I get readings of 0 ohms to 83K ohms and 83K ohms to 0 ohms between the centre tab and the outer wiper tabs as I rotate the shaft. (The schematic shows 75K.) So far, so good.

    However, when I begin connecting wires one reading stays at 0 ohms as I rotate the shaft. This occurs as soon as I connect the wire from the antenna coil to the wiper tab. The continuous 0 reading occurs between the centre tab and the outer tab leading to the antenna coil.

    Is this normal? Does it suggest a problem with the coil?

    March 26, 2016 at 9:36 am #7625
    Les Dickson
    CVRS Member

    Adjustment to Resistance Reading
    The reading I get across the centre and outer wiper tabs is not actually 0 when the coil is attached to the volume control. By using a finer setting I get a reading of 34 ohms when the volume switch is off and a range of 23 to 40 ohms when rotating the volume shaft.

    March 26, 2016 at 10:39 am #7626
    Peter Heembrock
    Forum Participant

    After having a quick look at the schematic from radio museum I see that the antenna coil will dominate the volume control resistance reading since the coil will be about 50 ohms or less so yes this seems ok…the coils seem ok too…if they read zero there would be a problem ( or open ). Usually in sets like this the antenna coil usually fails open. So all sounds good so far.

    PH

    March 26, 2016 at 8:34 pm #7628
    Les Dickson
    CVRS Member

    Thanks ever so much for your help Peter. It’s much appreciated.

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