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ZL1ANM > OLDSET 20.07.09 21:42l 34 Lines 1302 Bytes #999 (0) @ WW
BID : ZL1ANM-569
Read: GUEST
Subj: Re: Interest in vintage radios
Path: IZ3LSV<IK2XDE<DB0RES<ON0BEL<ZL2BAU<ZL1AB
Sent: 090720/2033Z @:ZL1AB.#06.NZL.OC #:31680 [AUCKLAND] FBB7.00i $:ZL1ANM-569
From: ZL1ANM@ZL1AB.#06.NZL.OC
To : OLDSET@WW
>You mean you never found a hum bucking coil,Neil.
>
>....don't know why we always found that amusing :-)
>
>
>
>
>==================================================================
>
>I remember pulling old radios to pieces for spare parts in the mid-60's
>when I was a teenager, and yes, the early models did have a winding on
>the loudspeaker through which the B+ was fed. It served a dual purpose
>as you say: B+ filter choke, and magnetising current for the speaker's
>iron core. Hum would become a problem if the winding's leads or speaker
>audio leads happened to become reversed by a careless serviceman, since
>it was intended that the hum induced in the magnet core would negate
>any hum present in the audio output.
>====================================================================
>73 from Ian, G0TEZ...
Wasn't a hum bucking coil a single winding on an iron core that was
connected in series with the loudspeaker and positioned close to the
power transformer in order to pick up some hum voltage? Wasn't there
a wirewound pot also, to allow for minimizing the level of hum. And
the phasing had to be correct, else it wouldn't work.
73 de Neil ZL1ANM
T4 1.5à24
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