[Amps] Looking for a design for a single 4cx250b tube on 50 Mhz-six meters.

[craxd]

Bill,

Wide open by cutting the bias as far down as it would go. Maybe -20 to 
-30 Vdc at the most. On top of driving the dickens out of the tube, 
maybe 20 watts pep going in, some running more. Plus this amp doesn't 
have any type of swamping for a large transceiver to drive it. Needless 
to say, the tube wont last that long. I know some others who built them 
running 3000 Vdc, with a higher screen of about 400 VDC if I remember 
correctly. They'd run for a while, but the major complaint was the tubes 
wouldn't last long. The best I've seen them run at is about 2500 vdc 
plate, and about 300-350 Vdc screen. Bias adjustment running from -30 to 
-90 Vdc. The output was about 400 PEP a piece. To be honest, I think the 
rating on that Pride might have been 600 watts input. That would have 
been about 300 watts out, unless they're saying 600 watts out, which in 
my opinion is ridiculous. I'd have to read the original manual to see 
what it says.

Will Matney


Bill Fuqua wrote:

> Wide open, does that mean class C SSB?
> 73
> Bill wa4lav
>
>
> At 03:10 PM 10/12/2004 -0400, craxd wrote:
>
>> Bill,
>>
>> That amp, which really said was an amateur amp, was mostly sold to 
>> the 11 meter folks. The larger the numbers, the more they sold it 
>> for. I've seen it's schematic listed now on several amateur sites, 
>> less the text portions. Some were built however, with a band switch. 
>> Actually, that was supposed to be 600 PEP, which is way over what it 
>> should be. The ones I've actually had my hands on did about 450-500, 
>> but that was wide open. I wouldn't run it that way very long. Cut 
>> back to where it should be, it will run ok. I just dont like the 
>> screen and bias circuit in it that well. This can be changed though 
>> in a homebrew amp anyhow.
>>
>> Bill Fuqua wrote:
>>
>>>     The manual claims that a single 4CX250B will produce 600 watts 
>>> peak output. It has unregulated bias supplies as well.
>>> I wonder if that is figuring peak voltage squared divided by 
>>> resistance rather than PEP value.
>>>
>>> 73
>>> Bill wa4lav
>>>
>>> At 12:12 PM 10/12/2004 -0400, craxd wrote:
>>>
>>>> Ken,
>>>>
>>>> If six meters is all your wanting, no higher, I'd take a look at 
>>>> the way the old Pride amplifier was made. The schematic for it is 
>>>> all over the net. The input and output tank will need to be changed 
>>>> for six meters but the circuit is almost the same. Pride made two 
>>>> models of this (both the same), I think one was called KW-One and 
>>>> the other a 300 if I recall. It dont have the best regulation for 
>>>> the screen and G1 bias, but it did work up to 10 meters using one 
>>>> 4CX250B.
>>>>
>>>> http://cbtricks.com/Amp/pride/index.htm
>>>>
>>>> Will Matney
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>>>
>>>
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