# Re: Tube watts & volts

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On Fri, 02 Jul 1999 22:23:07 -0600 Tesla List <tesla-at-pupman-dot-com> writes:
>Original Poster: Ed Phillips <evp-at-pacbell-dot-net>
>
>Tesla List wrote:
>>
>> Original Poster: Grayson B Dietrich <electrofire-at-juno-dot-com>
>>
>> I'm a little confused on two areas,
>>
>> Is the voltage rating of a tube, say, 1500 for an 811-A, peak or
>rms?
>
>	Doesn't matter much, if the tube isn't gassy.

That means, the getter is still a shiny silverish color, and not white?

You're not
>going to run
>it for long periods of time and the plate lead does come out the top,
>so
>the stress on the glass is small.

I've gleaned that the 1500 is a DC, static rating. I was planning on
removing windings from the secondary of a MOT, and using it to power my
setup. The current output of two such Xfrmrs I have is 2100Vac. I'm
thinking I'll drop that till peak is 1600 or so. Just to be safe.

>
>
>> The other question I have is the wattage an 811-A can handle. In the
>back
>> of Brent Turner's book, it is listed as having a plate wattage
>capability
>> of 65 watts,
>
>That's plate DISSIPATION (the difference between the total power input
>and the total power delivered to the load circuit).  If the oscillator
>efficiency is 75% (kinda low), the power output of the tube would be
>about three times the plate dissipation.  Says you should easily be
>able
>to push a couple of hundred watts or more out of the 811A.

How is the figure of about 3X for 75% efficiency arrived at? I recall
that most class-C amplifiers run at about 80% efficiency... is that
correct?

I'm trying to decide how to find the current I'll need from the plate
transformer. Is that equal to the plate current, with the grid current
added in somehow? (How is that done?)

>
>Ed
>
>

I know I'm asking  a lot of begginner questions for tube work, so a
great-big megathanx to anyone who's answering my posts.

Grayson Dietrich

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