Jeff,
You may have to find some older tube books on ebay or one of the online book
sellers from the 40's and 50's. You may also want to give Eimac, or maybe MPD
(GE) a call and see if they have any other sheets available with different
voltages. Just tell an engineer what you need and they may help. Another place
to look is an older amp manufacturer who used the tube with the voltages your
looking at. Sometimes they can have old test data sheets from jobs of the past.
Best,
Will
*********** REPLY SEPARATOR ***********
On 1/26/06 at 11:28 AM Xmitters@aol.com wrote:
>In a message dated 1/26/06 10:13:31 AM Central Standard Time, r@somis.org
>writes:
>
><< The curves for 500v may be converted to other voltages by applying the
> 3/2 power law.
> >>
>The 3/2 power law is only applicable over a fairly narrow range. This
>approach is especially problematic when the control grid voltage is
>positive at the
>published screen voltage and it goes negative at the desired screen
>voltage.
>You also run into problems when calculating where the zero plate current
>line is
>going to be with the desired screen voltage compared to the published
>screen
>voltage. This comes about when you ratio out the desired versus published
>screen voltage. To scale the grid voltage axis, you then multiply the
>published
>control grid voltages by this scale factor. Well, this approach does not
>work
>when you have to relocate the zero control grid voltage point at the new
>screen
>voltage. Zero times anything is zero.
>
>I verified this by examining several tubes that have curves for more than
>one
>screen voltage. I chose an observation point (plate voltage and plate
>current) on one curve, then noted the grid voltage for that point. I found
>the same
>observation point on the other set of curves. I then applied the 3/2 power
>law.
>In some cases it was close, in other cases it was off by a mile.
>Especially
>in the case where the grid voltage for that observation point stats out
>mapped
>with a positive grid voltage, and then goes negative at the higher screen
>voltage.
>
>For relatively small deviations in screen voltage from published to
>desired,
>the 3/2 law works quite well.
>
>
>Jeff Glass, BSEE CSRE
>Northern Illinois University
>WB9ETG Since 1970
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