> w5jgv.com/downloads/RCA%20*833A*.pdf
> shows a pair of them can run the legal limit and a single one can get
> about 1200 PEP out, but this is with a plate dissipation of only 350
> watts so a lot depends on the duty cycle. The filaments ae 10V @ 10A
> thoriated tungsten so unlike many of the big power tubes the
> filaments are not terribly power hungry.
I would be somewhat concerned about the quality of an amplifier using
the 833. Both the Matchlett and RCA data sheets show power outputs
in the 200 - 250 W range per tube in "Class B telephony" service.
I don't know if that is low level AM or if the efficiency falls off
that much between class C (plate modulated or FM service).
The 1980 Handbook does not give power output but indicates that
efficiencies of "55 to 65% can be expected." The design was for
1 KW input in class AB2.
73,
... Joe, W4TV
> -----Original Message-----
> From: amps-bounces@contesting.com
> [mailto:amps-bounces@contesting.com] On Behalf Of Roger
> Sent: Tuesday, March 16, 2010 7:10 PM
> To: Greg Weinfurtner
> Cc: amps@contesting.com
> Subject: Re: [Amps] Building 833 Amplifier. Hints and Suggestions?
>
>
>
>
> Greg Weinfurtner wrote:
> > Hi all,
> > I am new to the list so be kind! I went through all of the
> > threads
> > on amps@contesting.com concerning an amplifier using 833's
> and pretty much
> > came up with very little usable information. Why 833's?
> Why do I still
> > deer hunt with a muzzle loader with just iron sites? Why do
> people still
> > build tube regens? Just 'cause I guess it is a challenge
> and the 833 is a
> > magnificent looking tube all aglow!
> >
> Others may not share my views but:
>
> I find the 833 intriguing but I've always thought it was
> ugly<:-)) OTOH
> I too have wanted to build up an amp using them.
> w5jgv.com/downloads/RCA%20*833A*.pdf
> shows a pair of them can run the legal limit and a single one can get
> about 1200 PEP out, but this is with a plate dissipation of only 350
> watts so a lot depends on the duty cycle. The filaments ae 10V @ 10A
> thoriated tungsten so unlike many of the big power tubes the
> filaments
> are not terribly power hungry.
>
> With forced air cooling they are referring to 40 cfm out of a
> 2" nozzle
> directly over the tube with the flow directed between the
> plate and grid
> connections. Using a "swamped grid" approach takes about
> 40-50 watts
> of drive for a pair of them to get over the legal limit out.,
> but that
> can vary widely depending on plate voltage.
>
> I think a pair of those with the ability to view them while running
> would be impressive.
>
> Due to the physical geometry I'd think (but don't know) that the
> isolation of the input circuitry from the output would take a
> bit more
> care than with modern tubes.
>
> I've been looking at the idea of building up a similar amp
> using a pair
> of the GU81M Russian tubes. Those things are BIG!
>
> more below.
> > I was an Electronic Design Specialist for Ohio
> University for
> > over
> > 22+ years and have built a hybrid solid state 160 meter SSB/CW 100
> > 22+ watt
> > transceiver (Using a pair of 6146's) from the ground up, (
> > http://oak.cats.ohiou.edu/~weinfurt/160mrindex.html
> )including a 500 hz CW
> > filter. Age is mid 50's and was in Tube/Solid State
> transition during
> > college years. Yep, slip sticks to calculators to SMD's.
> BSS (Bachelor of
> > Specialized Studies in Shortwave RF Engineering) is from
> 1994, so that and
> > being an EDS helped keep me in the loop until I recently retired.
> >
> > I have all the parts to put together 160 meter single band
> > amplifier. I realize that it is a low mu tube of about 35,
> and would
> > probably not make a great grounded grid tube... but maybe
> at 160 meters a
> > pair of them could reach legal limit with less than 100 watts input?
> >
> > I have 5 each of 833A pulls, with only 6 months of
> use. I got
> > these from the engineer in charge and he said that usual
> pull time is at
> > least over a year or unless some failure occurs. But, the
> owner of the
> > station demanded that he do it every 6 months no matter
> what the condition
> > and he kept the 'like new' ones. Yes they are old, 20 years or so.
> >
> > I would prefer help from someone who has actually used the
> > 833 in
> > some type of RF circuit. But anyone with engineering
> experience with a
> > behemoth of this type knowledge would be great! I plan to
> set up a web
> > page and with my progress to keep those helping informed of
> my advancement
> > into the past!
> >
> > Characteristics for the 833A are
> > at: http://oak.cats.ohiou.edu/~weinfurt/833A.pdf
> >
> >
> **********************************************************************
> > **************
> > Plan.
> >
> > 1 Two of them in parallel or Push-Pull?
> >
> Single band you can take your pick. Use link coupling with
> PP. Parallel
> is a bit simpler.
> > 2 Grid driven with a 55 ohm, 75 watt non-inductive resistor
> to ground.
> >
> > 3 Pi output network or Pi L ? Or Link coupled output?
> >
> Single band, take your choice.
> > 4 Operation is CW and occasionally SSB. Bias voltage on Cathode
> > developed
> > across about 60v Zener to ground?
> >
> According to the data sheet, you might want to run around -90
> as a stand
> by bias to limit dissipation.
> > 5 Power supply is capable of 3000 VDC at 1 Amp.
> >
> That "to me" appears to be a bit toward the low end for these. But
> running higher voltage gives a plate load impedance of over 10K ohms.
> > 6 Forced air cooling up from pressurized bottom chassis to
> box on top
> > housing tubes and output components.
> >
> No. Due to the rather unique physical geometry of these tubes the
> maximum cooling air is needed between the plate and grid
> seals keeping
> the temperature down to a max of 145C. 40 cfm from a 2"
> nozzle directed
> down and between the plate and grid terminals.
> > 7 Tubes mounted in vertical position. Heat sinks for pin
> connections.
> >
> That might be a tad unstable...BTW the only permissible mounting
> position according to the data sheet is vertical.
>
> 73 and good luck,
>
> Roger (K8RI)
> > Greg Weinfurtner AEE BSS
> > NS8O
> > 40192 State Route 689
> > Meigs County
> > Albany, Ohio 45710
> > United States of America
> > _______________________________________________
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> > Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> >
> >
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