[Amps] 4-1000 amp

[R L Measures]

On May 29, 2006, at 2:51 AM, Chris Pedder wrote:

> At 09:29 29/05/2006, R.L. Measures wrote:
>
>>   The 3-1000Z has a grid that does a marginal job of shielding the
>> input from the output -- which means it has more feedback-C than need
>> be.  The 3cx1200A7 is the external anode version of the 3-1000Z and
>> it apparently uses the same grid and filament.  Both tubes have a
>> reputation for squirreliness -- especially with higher anode PS
>> voltages.  Eventually, Eimac discontinued making the 3-1000Z and the
>> 3cx1200A7 evolved into the 3cx1200Z7, which has less feedback-C --
>> and better stability.  Unfortunately, the ...A7 and the ...Z7 are not
>> interchangable.
>
> I cannot help but wonder why you keep pedalling this one. I have  
> been, yet again, to the Eimac/CPI data sheets which read as follows:
>
>
> grounded grid capacitance in pf
>
>                      in          out          feedback
> 3CX1200A7            20          10.3          0.6
> 3CX1200Z7            17.6         9.7          0.8
>
> This does not accord with your comments. Are the Eimac figures  
> incorrect?

Yes.  On other sheets the Z7 has 0.08 pF, not 0.8pF.   Does it make  
sense that the improved version would have more feedback?
>
> Chris
>
>
>

R L MEASURES, AG6K. 805-386-3734
r at somis.org