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  • #12573
    BlaineA
    Forum Participant

    Hello all.
    just came across this Macroni model 80 radio, my winter project.Removing radio from cabinet and dusted the old girl I noticed something missing ,In the schematic the two components that I believe are crystals , 1 located under R4 other under R6 . ,And one is missing.Can these be replaced with a diode and if so what type.Will try to upload schematic..

    • This topic was modified 2 years, 8 months ago by BlaineA.
    #12576
    Dan Walker
    CVRS Member

    What you see under R4 and R6 are not crystals, they are bias cells. You can replace them with a small 1.5 battery, the kind you use in hearing aids.
    They just supply a negative voltage to the grid of the tub
    . Dan in Calgary

    #12577
    BlaineA
    Forum Participant

    Thank you very much .I assumed they were crystals as part list shows a listing for crystal.
    Learned something new.

    #12599
    Dan Walker
    CVRS Member

    I finally found some photos of the replacement of bias cells.. This is the system I use.
    The battery holders are a little big for the 1.5 volt batteries , so I hot glue the smaller batteries in place
    You can use any method you want , but make sure the polarity is correct.
    Dan in Calgary.

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