[Amps] The ongoing 4CX250B verbage!

[R at contesting.com]

On Apr 4, 2006, at 2:26 AM, Steve Thompson wrote:

>
>
> exray at bellsouth.net wrote:
>
>> Yes there are better tubes available today...but the old 4CX250 
>> family is the granddaddy of all of them. If you come across a pair, 
>> and they should be inexpensive,  there are many good designs which 
>> have been published thru the years.
> I reckon it's also a good apprenticeship. If you encounter the quirks
> that 4CX250s can throw at you, you'll learn a lot about tube amplifier
> design. Over here, you can buy them for the price of a beer or two so
> learning doesn't have to be tearful if things go wrong.

An important precaution with 250Bs is to use a shunt regulator at the 
screen so that reverse screen current can not cause a runaway condition 
that destroys the tube.  Also, in HF/MF service, it's not a bad idea to 
terminate the grid in a R, so as to improve VHF stability. - end
>
> Steve
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Rich Measures, 805.386.3734, AG6K, www.somis.org