[Amps] Has anyone ever actually build an 833A linear?

[Carl]

>   Mike Waters wrote:
>
>> How about adding a tertiary winding to the step-up transformer, and use
>> that for the out-of-phase neutralizing signal? One end of the winding to
>> ground, the other end to a neut. capacitor connected to the plate?
>
>> You may be right on the requirements of the drive signal to the swamped
>> grid. I have a couple of ideas there.
>
>   The thing about 833s boils down to when 1 kW INPUT was the rule, 813's 
> were available for $5 to $15 NOS each and a pair in P-P using B&W 1 kW 
> coil sets worked 160 to 10 meters class "B" for 1 kW in.  (look in 
> handbooks published before 1955)
>
>   833s were used in older (from the 40's) broadcast transmitters with no 
> fans or blowers for 500 and 1,000 Watts unmodulated carrier out with long 
> life and trouble free operation.  The power capacity of the 833 was just 
> not necessary for HAM HF operations.  One tube giving you 500 Watts was 
> frequently done, but only where GOOD pulls were available, few radio 
> stations stations using 833s removed a GOOD tube, unless a HAM worked 
> there and wanted a free used tube.  4-400s are in the same category, just 
> different transmitter makers.
> -- 
>   Ron  KA4INM - Youvan's corollary:
>                 Every action results in unwanted side effects.
>

Many hams have always run over the legal limit and a single 833 is 
equivalent to a pair of 813's power wise. Their service life was no 
different than most any other tube in BCB service. When RF output dropped 
they were swapped with the pair in the modulators and when the modulator 
current dopped they were finally replaced. They either went to hams or 
scrap.
 Running a pair of 250TH's were more common on the ham bands due to surplus 
availability and a very common socket, plus they worked a lot better at 20M 
and up. The 304TL, 450TH and 6C21 were also used and later a pair of 
4-400A's or the 4-1000A were everywhere.

Carl
KM1H