[AMRadio] Two 807s modulating 4D32 final tube in Viking1

WA5VGO hbrnut at suddenlink.net
Thu Jan 1 19:10:30 EST 2015

The 807's will be about 7000 ohms. The 4D32 will be about 3500 ohms. An exact match isn't necessary. I suggest finding the closes combination that will allow connecting the windings in parallel. The transformer (at least in theory) should be a little hardier if the windings are connected in parallel as opposed to series. 


> On Jan 1, 2015, at 5:33 PM, John King via AMRadio <amradio at mailman.qth.net> wrote:
> I am replacing he modulation transformer in a Johnson Viking 1 transmitter and need some experienced and knowledgeable input. to assist me., Does anyone know the approximate impedance of two 807 tubes with at least 600 vdc on the plates that the modulation transformer must match?
> Secondly, does anyone know the impedance of the 4D32 that the secondary of the modulation transformer must match?
> I have a Stancor  A-3893  60 watt poly-pedance multi-tap modulation transformer.The data sheet can be seen on the AM Window web site.
> I feel sure that it will match the two 807s to the single 4D32. It was used previously in the modulator circuit that used two 6146 modulator tubes  as shown in the ARRL handbooks of the 1960s. I need to know what taps to use. Has any used this poly-pedance modulation transformer in a modulator? Your input will be appreciated. Thanks and 73, John, K5PGW
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