[Amps] 3CX800 stray C to chassis?

[Conrad PA5Y]

Thanks Steve that is very useful.

Regards

Conrad


On 22/08/2017 21:48, Steve Thompson wrote:
> Some years ago I measured some valves, including 3CX800. I don't think 
> I have kept the results but the general result was that the C was 
> about twice the data sheet value, and wasn't changed by the mechanical 
> setup unless the metalwork was really close - much closer than you 
> would want when looking at a layout.
>
> Steve
>
>> As I do not (yet) own a decent LCR meter does anyone have a decent 
>> ball park figure for the stray C to chassis for a 3CX800A7? The side 
>> walls are 1.25 inches away from the tube and the lid is 2.5 inches 
>> above.
>>
>>
>> Also thanks for all the help with my previous questions. I should 
>> mention that this is a retrofit to an existing 2m amp and C1 is 6pF 
>> maximum and I would like to use this part if at all possible.
>>
>>
>> I have a design that works on paper for strays C of 4pF with a Q of 8 
>> using an L-Pi-L configuration as recommended by a few of you. The 4pF 
>> stray value does not seem unreasonable but it is a guess. I am sure 
>> that someone must have measured this.
>>
>>
>> Regards
>>
>> Conrad PA5Y
>
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