On Fri, 18 Dec 1998 10:54:06 -0800 Rich Measures <measures@vc.net>
writes:
>John Fielding wrote --
>>>What's the difference?
>>
>Carl Heuther, KM1H, wrote --
>>The 250R has a minute (Eimacs word) .2pf increase in output C over
>the
>>7580. Both have a higher perveance than the 250B and require a
>slightly
>>more negative bias voltage.
>>At 1500V Ep any version can be made moderately clean. At 2000V they
>are
>>horribly dirty.
>
>? Carl: . By looking at any of the constant-current curves, one can
>
>see that the closer the instantaneous anode/plate voltage comes to the
>
>screen's supply.V, the greater the departure from ideal straight-line
>linearity. On Eimac's constant-current curves for a screen
>potential
>of 400v for the 7580]4cx250R, the curve for 1.2a is quite flat between
>
>2000v and 600v. Thus, with a supply potential of 2000v, 1400v of
>rather
>linear movement in the instantaneous anode potential is possible.
>However, if a 1500v supply were used, only 900v of linear movement in
>instantaneous is possible, and the most linear part of the curve
>between1500v to 2000v is lopped off. How could eliminating the most
>linear part of the curve make the tube "horribly dirty"?
>- cheers, Carl
Since you believe what is published Rich ( when it is convenient ) how
come you cant agree with published Eimac results?
I also tend to disbelieve claims that I can not verify with HP quality
test equipment. You make a lot of claims that I can not verify here with
a similar amp.
The consensus from several continents appears to agree that the
7580/4CX250R is dirty at higher Ep. Why do you always want to play word
games and ignore some basic facts supported by measurements?
Please, dont repeat the old canned drivel...try something new for a
change. You are beginning to sound like ur old buddy ...
73 Carl KM1H
>
>Rich...
>
>R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
>
>
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