[Amps] Homebrew is back..

[Vic K2VCO]

I am presently running one graphite-plate (WWII vintage) 813 and one metal-plate RCA 813 
in my class-C amplifier. I'm running them at about 2050v and 500 ma in CW service, and I 
haven't noticed any color on the plate of the metal one. I get a solid 800w out on most 
bands. I am planning to boost the primary voltage of the plate transformer.

I am presently looking for more NOS 813s.

On 3/29/2011 9:17 AM, Bill Fuqua wrote:
>      I have seen tantalum plate 813s made in the 60s.  RCA made them if I
> recall.
> They actually had more area than say a 4-125A which has the same dissipation.
>
> It just gets a little hotter and brighter to dissipate the heat via radiation.
> Just like the 4-125A, 250th etc.
>
> 73
> Bill wa4lav
>
> At 01:09 PM 3/29/2011 -0400, Diane&  Edward Swynar wrote:
>> Hi Carl,
>>
>> "...Tap the 10M coil in the center with the Tune cap which gives a 4X stepup
>> for the required C. Do not add a seperate L coil. The last 4x 813 amp I
>> built used the vacuum variable with the tap and it ran full power even at
>> the high end of 10M."
>>
>> ********************************************
>>
>> Yes, thanks for that info...
>>
>> A very nice classic example of that very technique may be seen in early/mid
>> 60's editions of the ARRL HANDBOOK: the piece I'm thinking of deals with
>> mono-band amplifiers, all employing paralleled 813s...
>>
>> MUST READING if you're thinking of ever using one of these venerable jugs on
>> 10...!
>>
>> BTW Carl, have you ever seen an 813 WITHOUT that rugged graphite plate...? I
>> found a couple at a Hamfest a few years ago wherein the plates---I
>> swear---look like the plates used in 811A's, only fed with steroids!
>>
>> "Tin plate" construction all the way. How they can dissipate the graphite
>> plate's 125-watts I do NOT know...
>>
>> I've never tried them on the air yet---and can find no reference in the
>> books on them either...
>>
>> ~73~ de Eddy VE3CUI - VE3XZ


-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/