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Thread: Does the Filld Coil in this National amp act as a choke ?

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    Member HaroldBrooks's Avatar
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    Does the Filld Coil in this National amp act as a choke ?

    I asked that question about another one of my old amps a while back (Supro Supreme circa 1949) and the answer was no for the below Supro amp :

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    But for the amp below (A Valco cousin made by National), I believe the Field coil in the below National 1212 amp also serves as a power choke., is this correct ?

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    Quote Originally Posted by HaroldBrooks View Post
    I asked that question about another one of my old amps a while back (Supro Supreme circa 1949) and the answer was no for the below Supro amp :

    Click image for larger version. 

Name:	Supro 1600.jpg 
Views:	25 
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ID:	56111



    But for the amp below (A Valco cousin made by National), I believe the Field coil in the below National 1212 amp also serves as a power choke., is this correct ?

    Click image for larger version. 

Name:	National 1212.jpg 
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ID:	56112

    In the National 1212 amp the field coil definitely serves as a PS filter choke.

    In the Supro schematic I don't see a field coil, but if there is one it is most probably also wired as filter choke.

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    Don't forget the joker g1's Avatar
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    I think I've seen field coils wired from B+ to ground, in which case it does not act as a choke, but may be acting as 'ballast' to load down the supply.
    In your Supro example, I think this is the whole schematic, with the field coil shown as '1000ohm 25W'. If so, yes it is acting as a choke, not sure why it would not be deemed as so, unless there was confusion about whether it was a choke or a resistor.


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