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Re: [TenTec] Transformer and schematic help needed

To: Roger Hughes <roger.h@comcast.net>
Subject: Re: [TenTec] Transformer and schematic help needed
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Reply-to: geraldj@storm.weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 30 Dec 2008 20:41:50 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
On Tue, 2008-12-30 at 14:24 -0600, Roger Hughes wrote:
> HI Gerald. Old heathkit SB23b.

SB23B won't do 1500 volts, nor 3/4 amp. Nor will the SB-200 power
supply.

> I can't remember model. for transformer. Also 
> the SB-200 heath amp can be easily  converted to 6m Amp. My friend did one, 
> but I have no idea. He got the mod off the web.Each one if those should be 
> cheap. They may be worth a check. 73 Roger.

Not when I have a box with three good 4CX250B in parallel for 6m. I
don't need a power supply, Jeff does, and he also has the final built
already.

Also three grid driven 4CX250B take only 10 watts of drive, while the
converted SB-200 would take at least 100 watts (because its grounded
grid instead of a gang of grid driven tetrodes). And probably won't put
out the 1150 watts key down that the three 4CX250Bs will.

73, Jerry, K0CQ

> ----- Original Message ----- 
> From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
> To: <tentec@contesting.com>
> Sent: Tuesday, December 23, 2008 12:17 PM
> Subject: Re: [TenTec] Transformer and schematic help needed
> 
> 
> > On Tue, 2008-12-23 at 09:05 -0800, Jeff wrote:
> >>
> >> Wanted Transformer close to 1500V @.750Ma
> >>
> >> Hello Folks I am looking for a transformer that is 120 volt primary and 
> >> around 1500 volts on secondary with at least .750Ma rating. I do not want 
> >> any microwave oven transformer’s… Also don’t want any expensive PW Dahl 
> >> type I simply can not afford them although I wish I could.  I am retired 
> >> and on fixed income and I am trying my best to make  home brew 6 meter 
> >> amp running a trio of 4CX250B tube’s And all I need is now to make the 
> >> power supply. Any help would be most appreciated.
> >>
> >> Any one having great schematics they would send of a power supply would 
> >> be great to.
> >> Many thanks and Merry Christmas to all. Jeff
> >>
> >
> > So you wish a DC supply that puts out about 2 KV at 3/4 amp DC? That's a
> > lot of power on a 120 volt line, especially figuring the line current
> > waveform won't be nice, but will be peaked from the capacitor input
> > filter.
> >
> > Look for something like a Dentron MLA-2000 or 2500. It ran a pair of
> > 8121 at about that voltage and current. New PA tubes are a serious
> > expense so a used amp needing tubes tends to sell fairly cheaply.
> >
> > Look for a collection of control transformers with 600 volt and 480/240
> > primaries. Run them backwards with the primaries in series to get 750 or
> > so volts for a voltage doubler. What you save in transformers though
> > will be eaten up in filter capacitors.
> >
> > Last I heard Dahl was retiring due to health problems and closing the
> > business so that source may be totally gone, except used.
> >
> > 73, Jerry, K0CQ
> >
> > 

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