Yes for many years 833s were solid performers in a number of 1KW
(output) Am Broadcast transmitter designs. That means at least 4 KW PEP
output power or about 5KW pep input. Typical setup two in the RF and two
class B push pull modulators. They typically out performed the newer
4-400 designs in both power margin and life. The only reason 4-400s
became popular was the lower drive requirement which to me was a bad choice.
Roger wrote:
>
> Joe Subich, W4TV wrote:
>
>>
>>
>>> 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 data sheet is interesting in that is shows a wide range of output
> power from the 200-250 watts above to over 1200 watts. They show a
> maximum plate voltage of 3000 and turn around and put more than 4000 on
> the plate with a resulting PEP output of over 1600 watts for a pair of
> tubes.. It appears to be more than just the class of operation. IOW
> reading the sheet it appears if you can keep the tube cool within specs
> be it convection cooled or forced air cooled, (145 deg C on grid and
> plate seals) the tube can do the job. OTOH I have no idea as to what
> the IM products are at these various voltages and power.
>
> Just like the Russian GU81M they appear to be capable of a lot more than
> you would expect. A pair of the GU81Ms for instance is listed at being
> capable of 3KW out in SSB, or CW with no forced air. One user told me
> the only way to hurt one would be to take a hammer to it. I don't
> think the 833A is quite that versatile with only a 350 watt plate, but
> still...
>
>> 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.
>>
>>
> To me the data sheet would indicate a pair of them are certainly capable
> of the legal limit out if you don't exceed the seal temps or melt the
> plates.
>
> 73
>
> Roger (K8RI)
>
>> 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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>>>>
>>>>
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>>>
>>>>
>>>>
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>>>
>>>
>>
>>
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