On Sun, 27 Sep 98 12:47:01 -0800 Rich Measures <measures@vc.net> writes:
>> >this would require very large wattage resistors to
>>>meet eimacs 50 joule and less energy dissapation,
>
>I doubt that the 50 joule limit is needed for larger tubes.
Far far less Rich. The YC-156 as an example carries an Eimac
recomendation of 4 Joules limiting. They go on to suggest 10 Ohms at a
minimum of 200W.
Looking thru some spec sheets it appears that a wide variation in
limiting exists amongst tubes.
The YC-156 appears to be a nice compromise between the 3CX3000A7 and the
8171 inasmuch the Ep can still be modest and it can do 7500W without an
IPA if driven by a FT1000D.
A small LA-1000NT type of IPA will drive it to 15KW. No socket, grid or
screen supplies makes it attractive.
Th AM CBers dont like the tube because it can not take their typical
brain dead abuse and lack of design ability....so it is still pretty
cheap on the "pull" or expired warranty date code market
>>......
>>>Igor
>>
>>High power and cheap are not often attainable Igor!
>
>amen, Carl.
>
>>At 9KV you will need several resistors in series to stay within the
>>individual voltage ratings.
>>225W wirewound resistors are not that expensive new; about $11 each
>for
>>Ohmite at Mouser.
>>
>A problem is that Ohmite 225w rated resistors do not have a fault
>rating.
> For a fault-rated resistor, one needs to go to Cesivid, Inc. - 716
>
>286 7610 Or, one could perform fault tests on non-fault rated
>resistors to see where they come apart. . . My experiences with
>tetrodes with handles suggests that limiting I fault-peak to c.100
>times
>the anode/plate I rating is adequate. Thus, for an 8171, 25 ohms will
>
>probably do the job, provided that it does not break down during a
>glitch.
Good point and probably followed by the Continentals of the world. I cant
ever remember seeing anything but Ohmite quality in the many commercial
5-10KW amps I have worked on in the past 35 or so years. I have several
surge assemblies here that were removed from scrapped amps and they all
use the generic 100-200-225W resistors.....no Carborundums, etc.
73 Carl KM1H
>- later, Igor.
>
>Rich. Measures. Web site: www.vcnet.com/measures
>
>
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>
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