> Gentlemen,
>
> I posted to this reflector late last year with a query regarding using
the
> DJ5RE design with a GS35b on 144MHz - with great success! I am happy
to
> report that the project is coming along just fine, with the only
problem to
> date being the acquisition of suitable finger-stock to make a 'socket'
for
> the tube. I know I can do this by other means, but I'd like to take
this
> route...
>
> However, this is not the point of my posting.
>
> I'd like to feed the anode of the GS35b with 4 to 4.5Kv DC. Many
others have
> had great success with this level of voltage on the anode so I've
chosen
> this as my goal.
>
> I've managed to get my hands on an HV Transformer which features a
> 3950-0-3950 secondary, and a 10-0-180-200-220-240 primary. The only ID
on
> the unit is "M.E.P. M1921 SR/T 2468".
>
> The question is: How do I tame the beast so as to provide the required
level
> of DC from a 240v AC supply?
>
> I immediately thought of placing a 240/110 transformer in the primary
to
> feed the 'main' transformer with 110v onto the 240 primary tapping.
This
> would be fine, except that sourcing such a transformer in the UK has
proven
> difficult.
>
> So, a friend has suggested using a full-wave rectification setup with
a
> filter choke - but by my calculation this requires a choke of some 5H
or
> more! How do I build such a choke, or where can I purchase one?
>
> Maybe you know of a better way? Any help/suggestions would be greatly
> appreciated.....
>
> Happy New Year, Chaps!
>
> Phil Smeaton
> G0HSS
>
Phil,
John Nelson G(w)4FRX published a design for a Thyristor controlled HV
supply as part of a series on the 4CX250/350 in the " Short Wave
Magazine", June '81 to Jan '82. This enabled a wide range of control of
final HT voltage, along with regulation due to feedback.
I'm not too sure how many were built, or whether RFI problems were
significant. The article claimed that these could be tamed.
Hope this helps and good luck with the amp.
73 and HNY,
Steve G8IZY.
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