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  • #11211
    Bruce Hamilton
    Forum Participant

    The power supply filter choke for the radio I am trying to restore is open-circuit. The radio is a deForest D-637 and the choke is T9 on the circuit diagram. I have found a part no. a manual for a Rogers R-237 has the identical schematic. Any suggestions where I can find the ratings for the choke will be much appreciated.
    Bruce Hamilton

    Alistair Thomson
    CVRS Member

    For a design like the Rogers/DeForest with these 50µF caps, the coil inductance should be between 5 – 20 Henrys, with wire and insulation which can easily handle the current (which I haven’t calculated) and the voltage (say 250V) supplied to the circuit. I haven’t looked at the following link, because the software mentioned is for PC only, but it may (or may not) give you the info you need, after a bit of ferreting about for current / voltage estimates:

    Alternatively, you could take the very reasonable view that the issue with the existing coil is most likely to be in the flying lead connections, and you can find out, by unwinding, where the disconnection problem is. Much cheaper, and a bit more fun, than just replacement! As long as you’re prepared to walk away from the debris if it doesn’t work out – but then you’re still no worse off.

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