[Amps] Sweep tube amp

Thu Jul 2 11:29:52 PDT 2009

The sweep tube amplifier shown in the link was custom built for Browning by a now defunct company?that was located in?Joliet, Illinois called Contex. (Also known by many other names,?some of which were?BROWNING and ABC). It was a no-bias sweep tube amp that used two tubes with 13 to 17?watt plate dissipations running at 100 watts,?(and more unless properly tuned). It was one of the 'dirtiest' amplifiers ever built and went thru tubes like a hot knife thru butter. Cherry red plates in 30 seconds of keydown time and no cooling fans!?? Back then, (1960's), those 6JG6 tubes only cost a dollar (or less in quantity) each so?the tube abuse?didn't mean much at the time, but if you price them now you will find?those tubes and all 'equivalent' tubes are?very rare and high priced. The rareness was caused in a large part by the CB use of these CONTEX / ABC / BROWNING, amplifiers by operators who usually didn't know how to tune them. At least Contex rated them as 60 watt amplifiers based on their typical maximum output while Browning rated them at 180 watts which was the theoretical input power that would have been required for a 60 watt output. They had about a 10 DB gain for input powers less than 6 watts peak,?and were single banded to 11 meters.?The outside sheet metal and chassis design may have been supplied by?Browning, (Laconia, New Hampshire),?so that the amplifier would match the design of the Browning Golden Eagle CB radio.

?I?have enjoyed?researching the history for these cheap and dirty CB linears and have found that most, if not all, had originated as a result of ham operators trying to make a quick buck! Contex was just one more example of a HAM gone bad who got very rich as a result.
?One perfect example was the ham who started the D&A amplifier Company, (Scottsbluff, Nebraska),?who was so successful that he was frequently advertised?the perfect?example of a very successful NTI (National Technical School) graduate, and was shown next to his delivery van in many full page adds in various electronics magazines that were printed in the late 60's and 70's. ( I believe the D&A stood for Delaney and Adams, but have never verified that fact ).

?Any other trivia anyone may have related to CB linears and their origins would be?welcomed as I have recently considered writing a book on the subject.

Dennis O.
dennis12amplify at aol.com
Living just outside Joliet Illinois

-----Original Message-----
From: ny9h <ny9h at arrl.net>
To: amps at contesting.com
Sent: Thu, Jul 2, 2009 9:02 am
Subject: Re: [Amps] Sweep tube amp

Big bucks,,,,,  for thi classic  "10 meter" amp....

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=190316129891

\bill

06:37 AM 6/27/2009, Felipe Ceglia - PY1NB wrote:
Hi Angel,

>I one recent CQ DL magazine, may 2009 (the one with the CW op YL on
>cover), there is a project for a funf-tube PL519 amplifier. If I recall
>it correctly it does not use a HV trafo, but for sure the output tank
>was PI.
>
>If anyone have any information about the Fuchreis tuning network, I
>would like to hear about it.
>
>73,
>
>Felipe - PY1NB
>
>Angel Vilaseca wrote:
> > Gentlemen,
> >
> > I just bought an old amp that uses 5 PL 519 TV sweep tubes in parallel.
> > As it reads on the box, it was home made on June 1983 by HB9 AWI.
> > The amp does not work anymore, but it is superbly built. The builder,
> > HB9AWI, obviously put a lot of effort into it.
> >
> > I would like to restore it. It is so well made and so typical of ham
> > state of the art at the end of last Century.
> > No inexpensive Russian power tubes were obtainable at these cold war
> > times! On the other hand, old color TV sets with sweep tubes still alive
> > were plentiful. The PL519 had the reputation of being quite rugged. Most
> > frequently, it was the line output power treansformer of the TV set that
> > failed, not the tube.
> >
> > Unfortunately, there was no schematic included with the amp..
> >
> > The seller told me the design of the circuit was by DL9AH. It is quite a
> > non-typical design:
> > For one, the tank circuit is not a Pi, nor a Pi-L! It is called a
> > Fuchkreis. It seems it was invented by an Austrian ham called Fuchs. I
> > never saw anything like it.
> > The power supply is a transformerless design. Apparently, it delivers +
> > and - 300 Volts. So needless to say, the cathode circuit of the five
> > PL519s is quite unconventional too. The bias circuit uses two pentodes,
> > a PL 504 (a b&w TV sweep tube) and a smaller one. Never saw anything
> > like this either!
> > There is a separate 10-turn potentiom
eter for each PL519 to adjust the
> > current through each tube. Quite sensible when you use five second-hand
> > tubes, that may have already lived a number of years as sweep tubes in
> > TV-sets.
> > The power supply, the bias circuit, the relays circuit all have lots of
> > VK200s and decoupling caps everywhere.
> >
> > As I just said, in a true ham spirit, it may use cheap tubes, but
> > obviously a lot of care was used to design and build this piece of
> > equipment.
> >
> > So, really, I would like to restore it. I tried finding the DL9AH design
> > on the web, but no luck!
> >
> > Does the phrase " Sweep tube amp, DL9AH design" ring a bell? Especially
> > for european hams?
> >
> > Any information about the design, or schematic welcome.
> >
> > Vy 73
> >
> > Angel Vilaseca HB9SLV
> >
> >
> > _______________________________________________
> > Amps mailing list
> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
>--
>Felipe Ceglia - PY1NB
>-------------------------------------------------------------------------------------
>PR1T team member /// Rio DX Group member /// Araucaria DX Group member
>http://www.dxwatch.com /// http://reversebeacon.net ///
>http://riodxgroup.dxwatch.com
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